Rails Validation Check Again Null and Blank
Active Record Validations
This guide teaches you how to validate the state of objects before they go into the database using Active Record's validations feature.
After reading this guide, you will know:
- How to use the built-in Active Tape validation helpers.
- How to create your own custom validation methods.
- How to work with the error letters generated by the validation process.
Chapters
- Validations Overview
- Why Use Validations?
- When Does Validation Happen?
- Skipping Validations
-
valid?andinvalid? -
errors[]
- Validation Helpers
-
credence -
confirmation -
comparison -
exclusion -
format -
inclusion -
length -
numericality -
presence -
absence -
uniqueness -
validates_associated -
validates_with -
validates_each
-
- Common Validation Options
-
:allow_nil -
:allow_blank -
:message -
:on
-
- Strict Validations
- Conditional Validation
- Using a Symbol with
:ifand:unless - Using a Proc with
:ifand:unless - Grouping Conditional validations
- Combining Validation Weather
- Using a Symbol with
- Performing Custom Validations
- Custom Validators
- Custom Methods
- Working with Validation Errors
-
errors -
errors[] -
errors.whereand error object -
errors.add -
errors[:base] -
errors.clear -
errors.size
-
- Displaying Validation Errors in Views
1 Validations Overview
Hither'due south an example of a very uncomplicated validation:
class Person < ApplicationRecord validates :name , presence: truthful end irb> Person . create ( proper name: "John Doe" ). valid? => true irb> Person . create ( name: nil ). valid? => false As you lot can see, our validation lets u.s. know that our Person is not valid without a proper name attribute. The 2d Person volition not be persisted to the database.
Before we dig into more details, let'south talk about how validations fit into the big picture of your application.
1.1 Why Utilize Validations?
Validations are used to ensure that only valid data is saved into your database. For case, information technology may be important to your application to ensure that every user provides a valid email address and mailing accost. Model-level validations are the best style to ensure that but valid information is saved into your database. They are database agnostic, cannot exist bypassed by cease users, and are convenient to test and maintain. Rails provides built-in helpers for common needs, and allows y'all to create your own validation methods too.
In that location are several other ways to validate data before it is saved into your database, including native database constraints, client-side validations and controller-level validations. Hither'southward a summary of the pros and cons:
- Database constraints and/or stored procedures make the validation mechanisms database-dependent and can make testing and maintenance more difficult. Withal, if your database is used by other applications, information technology may be a good idea to use some constraints at the database level. Additionally, database-level validations can safely handle some things (such as uniqueness in heavily-used tables) that tin can be difficult to implement otherwise.
- Client-side validations can be useful, just are generally unreliable if used alone. If they are implemented using JavaScript, they may be bypassed if JavaScript is turned off in the user'southward browser. Even so, if combined with other techniques, client-side validation tin can be a convenient way to provide users with immediate feedback as they employ your site.
- Controller-level validations can exist tempting to use, but often become unwieldy and difficult to examination and maintain. Whenever possible, it's a adept thought to go on your controllers skinny, as information technology will make your application a pleasance to work with in the long run.
Choose these in sure, specific cases. It's the opinion of the Runway team that model-level validations are the virtually appropriate in well-nigh circumstances.
1.2 When Does Validation Happen?
There are two kinds of Agile Record objects: those that correspond to a row inside your database and those that do not. When you create a fresh object, for case using the new method, that object does not belong to the database yet. In one case y'all phone call relieve upon that object information technology will be saved into the advisable database tabular array. Active Tape uses the new_record? instance method to make up one's mind whether an object is already in the database or non. Consider the following Agile Tape class:
class Person < ApplicationRecord terminate Nosotros can see how it works by looking at some bin/rails console output:
irb> p = Person . new ( name: "John Doe" ) => #< Person id: nil , proper noun: "John Doe" , created_at: cipher , updated_at: nil > irb> p . new_record? => true irb> p . relieve => truthful irb> p . new_record? => false Creating and saving a new tape will send an SQL INSERT functioning to the database. Updating an existing record volition transport an SQL UPDATE operation instead. Validations are typically run before these commands are sent to the database. If whatsoever validations fail, the object will be marked as invalid and Active Record will non perform the INSERT or UPDATE operation. This avoids storing an invalid object in the database. You can choose to have specific validations run when an object is created, saved, or updated.
There are many ways to modify the state of an object in the database. Some methods volition trigger validations, only some will non. This means that information technology's possible to save an object in the database in an invalid land if y'all aren't conscientious.
The post-obit methods trigger validations, and volition save the object to the database only if the object is valid:
-
create -
create! -
save -
save! -
update -
update!
The bang versions (e.g. save!) heighten an exception if the tape is invalid. The non-bang versions don't: save and update return faux, and create returns the object.
1.3 Skipping Validations
The following methods skip validations, and will salvage the object to the database regardless of its validity. They should be used with caution.
-
decrement! -
decrement_counter -
increment! -
increment_counter -
insert -
insert! -
insert_all -
insert_all! -
toggle! -
touch -
touch_all -
update_all -
update_attribute -
update_column -
update_columns -
update_counters -
upsert -
upsert_all
Note that save as well has the power to skip validations if passed validate: false equally an statement. This technique should exist used with caution.
-
save(validate: false)
1.4 valid? and invalid?
Earlier saving an Agile Tape object, Rails runs your validations. If these validations produce any errors, Rail does not salvage the object.
You can besides run these validations on your own. valid? triggers your validations and returns true if no errors were establish in the object, and false otherwise. Every bit you saw in a higher place:
grade Person < ApplicationRecord validates :name , presence: true end irb> Person . create ( name: "John Doe" ). valid? => true irb> Person . create ( name: nil ). valid? => false After Agile Record has performed validations, any errors found can be accessed through the errors instance method, which returns a collection of errors. By definition, an object is valid if this collection is empty after running validations.
Note that an object instantiated with new will not report errors fifty-fifty if it's technically invalid, considering validations are automatically run only when the object is saved, such as with the create or save methods.
class Person < ApplicationRecord validates :proper name , presence: true stop irb> p = Person . new => #< Person id: nil , name: nix > irb> p . errors . size => 0 irb> p . valid? => faux irb> p . errors . objects . get-go . full_message => "Proper name can't exist blank" irb> p = Person . create => #< Person id: nil , name: zip > irb> p . errors . objects . first . full_message => "Name can't exist blank" irb> p . save => simulated irb> p . save! ActiveRecord::RecordInvalid: Validation failed: Proper name tin't exist blank irb> Person . create! ActiveRecord::RecordInvalid: Validation failed: Proper noun can't be blank invalid? is the inverse of valid?. It triggers your validations, returning true if any errors were plant in the object, and imitation otherwise.
i.5 errors[]
To verify whether or not a particular attribute of an object is valid, you tin utilise errors[:aspect]. It returns an array of all the error messages for :attribute. If in that location are no errors on the specified attribute, an empty assortment is returned.
This method is only useful later on validations have been run, considering it only inspects the errors collection and does not trigger validations itself. It's different from the ActiveRecord::Base#invalid? method explained to a higher place because it doesn't verify the validity of the object as a whole. Information technology but checks to see whether there are errors found on an private aspect of the object.
class Person < ApplicationRecord validates :name , presence: true end irb> Person . new . errors [ :name ]. whatever? => false irb> Person . create . errors [ :name ]. any? => true We'll cover validation errors in greater depth in the Working with Validation Errors section.
2 Validation Helpers
Active Record offers many pre-defined validation helpers that you can use directly inside your class definitions. These helpers provide mutual validation rules. Every time a validation fails, an error is added to the object'south errors collection, and this is associated with the attribute existence validated.
Each helper accepts an arbitrary number of attribute names, so with a single line of code you lot can add together the same kind of validation to several attributes.
All of them accept the :on and :message options, which define when the validation should be run and what message should exist added to the errors drove if it fails, respectively. The :on option takes 1 of the values :create or :update. In that location is a default error bulletin for each one of the validation helpers. These messages are used when the :message selection isn't specified. Let'south take a await at each i of the available helpers.
2.1 credence
This method validates that a checkbox on the user interface was checked when a form was submitted. This is typically used when the user needs to agree to your application'southward terms of service, confirm that some text is read, or any similar concept.
class Person < ApplicationRecord validates :terms_of_service , acceptance: true stop This bank check is performed only if terms_of_service is non nil. The default error bulletin for this helper is "must be accepted". You can also pass in a custom message via the message option.
class Person < ApplicationRecord validates :terms_of_service , acceptance: { message: 'must be abided' } stop It can also receive an :accept selection, which determines the allowed values that will be considered equally accepted. It defaults to ['1', true] and can be easily changed.
grade Person < ApplicationRecord validates :terms_of_service , acceptance: { take: 'aye' } validates :eula , acceptance: { accept: [ 'TRUE' , 'accustomed' ] } end This validation is very specific to web applications and this 'acceptance' does not need to be recorded anywhere in your database. If y'all don't have a field for it, the helper will create a virtual attribute. If the field does exist in your database, the accept selection must exist set to or include true or else the validation will not run.
2.two confirmation
Yous should use this helper when you lot accept two text fields that should receive exactly the same content. For example, yous may want to confirm an email accost or a password. This validation creates a virtual attribute whose name is the name of the field that has to be confirmed with "_confirmation" appended.
class Person < ApplicationRecord validates :electronic mail , confirmation: truthful end In your view template you could use something like
<%= text_field :person , :email %> <%= text_field :person , :email_confirmation %> This cheque is performed only if email_confirmation is not nix. To require confirmation, make sure to add a presence check for the confirmation attribute (we'll have a await at presence later on in this guide):
form Person < ApplicationRecord validates :email , confirmation: true validates :email_confirmation , presence: truthful cease There is as well a :case_sensitive option that you can use to define whether the confirmation constraint volition exist case sensitive or non. This pick defaults to true.
class Person < ApplicationRecord validates :e-mail , confirmation: { case_sensitive: faux } end The default error bulletin for this helper is "doesn't lucifer confirmation".
2.3 comparing
This check volition validate a comparison between any two comparable values. The validator requires a compare option be supplied. Each selection accepts a value, proc, or symbol. Whatsoever class that includes Comparable can be compared.
form Promotion < ApplicationRecord validates :end_date , comparison: { greater_than: :start_date } end These options are all supported:
-
:greater_than- Specifies the value must be greater than the supplied value. The default error message for this option is "must be greater than %{count}". -
:greater_than_or_equal_to- Specifies the value must be greater than or equal to the supplied value. The default mistake message for this option is "must be greater than or equal to %{count}". -
:equal_to- Specifies the value must be equal to the supplied value. The default mistake message for this option is "must exist equal to %{count}". -
:less_than- Specifies the value must exist less than the supplied value. The default mistake message for this option is "must be less than %{count}". -
:less_than_or_equal_to- Specifies the value must exist less than or equal to the supplied value. The default error bulletin for this option is "must exist less than or equal to %{count}". -
:other_than- Specifies the value must be other than the supplied value. The default error message for this option is "must be other than %{count}".
2.iv exclusion
This helper validates that the attributes' values are non included in a given set. In fact, this prepare can be any enumerable object.
class Account < ApplicationRecord validates :subdomain , exclusion: { in: %due west(www united states ca jp) , bulletin: "%{value} is reserved." } end The exclusion helper has an option :in that receives the set of values that will not be accepted for the validated attributes. The :in pick has an alias called :within that you tin use for the same purpose, if you'd like to. This example uses the :bulletin option to show how you can include the attribute's value. For total options to the message statement please see the message documentation.
The default error bulletin is "is reserved".
two.5 format
This helper validates the attributes' values past testing whether they lucifer a given regular expression, which is specified using the :with choice.
class Product < ApplicationRecord validates :legacy_code , format: { with: /\A[a-zA-Z]+\z/ , bulletin: "only allows letters" } end Alternatively, you can require that the specified attribute does not match the regular expression by using the :without option.
The default error message is "is invalid".
two.half dozen inclusion
This helper validates that the attributes' values are included in a given fix. In fact, this set can be any enumerable object.
class Coffee < ApplicationRecord validates :size , inclusion: { in: %w(small medium large) , message: "%{value} is not a valid size" } end The inclusion helper has an selection :in that receives the set of values that volition exist accepted. The :in option has an alias called :within that yous tin can apply for the aforementioned purpose, if you'd like to. The previous example uses the :message option to evidence how you lot can include the attribute's value. For full options please see the message documentation.
The default error message for this helper is "is non included in the list".
two.seven length
This helper validates the length of the attributes' values. It provides a diversity of options, and so y'all can specify length constraints in different ways:
class Person < ApplicationRecord validates :name , length: { minimum: 2 } validates :bio , length: { maximum: 500 } validates :password , length: { in: half-dozen .. twenty } validates :registration_number , length: { is: six } end The possible length constraint options are:
-
:minimum- The attribute cannot have less than the specified length. -
:maximum- The attribute cannot have more than the specified length. -
:in(or:within) - The attribute length must be included in a given interval. The value for this option must be a range. -
:is- The attribute length must be equal to the given value.
The default mistake messages depend on the blazon of length validation beingness performed. You can customize these messages using the :wrong_length, :too_long, and :too_short options and %{count} as a placeholder for the number corresponding to the length constraint being used. Yous tin notwithstanding use the :message option to specify an error bulletin.
class Person < ApplicationRecord validates :bio , length: { maximum: 1000 , too_long: "%{count} characters is the maximum allowed" } end Note that the default error messages are plural (eastward.g., "is likewise short (minimum is %{count} characters)"). For this reason, when :minimum is one yous should provide a custom message or utilize presence: true instead. When :in or :within take a lower limit of one, you should either provide a custom message or call presence prior to length.
two.8 numericality
This helper validates that your attributes have merely numeric values. By default, it will match an optional sign followed past an integer or floating betoken number.
To specify that only integer numbers are immune, set :only_integer to truthful. Then information technology will utilise the
regular expression to validate the aspect'south value. Otherwise, it volition try to convert the value to a number using Float. Floatsouth are casted to BigDecimal using the column'southward precision value or 15.
course Player < ApplicationRecord validates :points , numericality: true validates :games_played , numericality: { only_integer: truthful } end The default error message for :only_integer is "must be an integer".
Besides :only_integer, this helper besides accepts the post-obit options to add constraints to acceptable values:
-
:greater_than- Specifies the value must be greater than the supplied value. The default error message for this option is "must exist greater than %{count}". -
:greater_than_or_equal_to- Specifies the value must be greater than or equal to the supplied value. The default error message for this choice is "must exist greater than or equal to %{count}". -
:equal_to- Specifies the value must exist equal to the supplied value. The default error bulletin for this choice is "must be equal to %{count}". -
:less_than- Specifies the value must be less than the supplied value. The default error message for this option is "must be less than %{count}". -
:less_than_or_equal_to- Specifies the value must exist less than or equal to the supplied value. The default error bulletin for this pick is "must be less than or equal to %{count}". -
:other_than- Specifies the value must be other than the supplied value. The default error message for this option is "must be other than %{count}". -
:in- Specifies the value must exist in the supplied range. The default error message for this option is "must be in %{count}". -
:odd- Specifies the value must be an odd number if set to truthful. The default error bulletin for this option is "must be odd". -
:even- Specifies the value must be an fifty-fifty number if set to truthful. The default error message for this pick is "must be fifty-fifty".
By default, numericality doesn't allow null values. Yous can use allow_nil: true option to permit information technology.
The default fault bulletin when no options are specified is "is non a number".
2.nine presence
This helper validates that the specified attributes are not empty. Information technology uses the bare? method to check if the value is either nil or a blank string, that is, a string that is either empty or consists of whitespace.
form Person < ApplicationRecord validates :proper name , :login , :electronic mail , presence: true end If you want to be sure that an association is nowadays, you'll need to test whether the associated object itself is present, and not the strange key used to map the clan. This mode, information technology is non but checked that the foreign key is not empty but also that the referenced object exists.
class Supplier < ApplicationRecord has_one :account validates :account , presence: true cease In order to validate associated records whose presence is required, you must specify the :inverse_of pick for the association:
If you want to ensure that the association information technology is both present and valid, you lot besides need to use validates_associated.
class Order < ApplicationRecord has_many :line_items , inverse_of: :guild cease If you validate the presence of an object associated via a has_one or has_many human relationship, it volition check that the object is neither bare? nor marked_for_destruction?.
Since false.blank? is truthful, if y'all want to validate the presence of a boolean field you should use one of the following validations:
validates :boolean_field_name , inclusion: [ true , imitation ] validates :boolean_field_name , exclusion: [ nil ] By using one of these validations, you volition ensure the value will Not be nil which would result in a NULL value in most cases.
2.10 absence
This helper validates that the specified attributes are absent. It uses the nowadays? method to bank check if the value is not either zip or a blank cord, that is, a string that is either empty or consists of whitespace.
class Person < ApplicationRecord validates :name , :login , :email , absence: true finish If you desire to be sure that an association is absent, you'll need to examination whether the associated object itself is absent, and non the strange primal used to map the association.
grade LineItem < ApplicationRecord belongs_to :social club validates :gild , absence: true cease In order to validate associated records whose absence is required, you must specify the :inverse_of option for the clan:
form Order < ApplicationRecord has_many :line_items , inverse_of: :guild terminate If you validate the absence of an object associated via a has_one or has_many relationship, it volition bank check that the object is neither nowadays? nor marked_for_destruction?.
Since simulated.present? is false, if you lot want to validate the absence of a boolean field you lot should apply validates :field_name, exclusion: { in: [true, simulated] }.
The default error bulletin is "must be blank".
2.11 uniqueness
This helper validates that the attribute'due south value is unique right before the object gets saved. It does not create a uniqueness constraint in the database, and so it may happen that 2 different database connections create two records with the same value for a column that you intend to be unique. To avoid that, you must create a unique alphabetize on that column in your database.
class Account < ApplicationRecord validates :email , uniqueness: truthful end The validation happens past performing an SQL query into the model'south table, searching for an existing record with the same value in that attribute.
There is a :scope option that you can utilise to specify one or more attributes that are used to limit the uniqueness cheque:
class Vacation < ApplicationRecord validates :name , uniqueness: { scope: :year , message: "should happen once per twelvemonth" } end Should you wish to create a database constraint to preclude possible violations of a uniqueness validation using the :telescopic option, yous must create a unique alphabetize on both columns in your database. See the MySQL manual for more details about multiple column indexes or the PostgreSQL manual for examples of unique constraints that refer to a grouping of columns.
There is also a :case_sensitive choice that you can use to define whether the uniqueness constraint will be instance sensitive, instance insensitive, or respects default database collation. This option defaults to respects default database collation.
class Person < ApplicationRecord validates :name , uniqueness: { case_sensitive: false } cease Note that some databases are configured to perform case-insensitive searches anyway.
The default error message is "has already been taken".
two.12 validates_associated
You should use this helper when your model has associations that always need to be validated. Every fourth dimension you effort to relieve your object, valid? will be called on each one of the associated objects.
form Library < ApplicationRecord has_many :books validates_associated :books finish This validation will work with all of the association types.
Don't utilize validates_associated on both ends of your associations. They would call each other in an infinite loop.
The default error message for validates_associated is "is invalid". Notation that each associated object volition contain its own errors collection; errors do non bubble up to the calling model.
2.13 validates_with
This helper passes the record to a separate class for validation.
course GoodnessValidator < ActiveModel :: Validator def validate ( record ) if record . first_name == "Evil" record . errors . add :base of operations , "This person is evil" cease finish end class Person < ApplicationRecord validates_with GoodnessValidator end Errors added to tape.errors[:base] relate to the country of the tape as a whole, and not to a specific aspect.
The validates_with helper takes a grade, or a listing of classes to use for validation. There is no default mistake bulletin for validates_with. You must manually add errors to the tape's errors collection in the validator form.
To implement the validate method, you must have a record parameter defined, which is the record to be validated.
Similar all other validations, validates_with takes the :if, :unless and :on options. If you pass whatsoever other options, it volition send those options to the validator form as options:
class GoodnessValidator < ActiveModel :: Validator def validate ( record ) if options [ :fields ]. any? { | field | record . send ( field ) == "Evil" } record . errors . add :base , "This person is evil" end finish finish class Person < ApplicationRecord validates_with GoodnessValidator , fields: [ :first_name , :last_name ] end Annotation that the validator will be initialized only one time for the whole application life bike, and not on each validation run, so be careful almost using case variables inside it.
If your validator is complex enough that you lot want instance variables, yous tin can easily use a plain old Red object instead:
course Person < ApplicationRecord validate do | person | GoodnessValidator . new ( person ). validate end finish class GoodnessValidator def initialize ( person ) @person = person finish def validate if some_complex_condition_involving_ivars_and_private_methods? @person . errors . add :base , "This person is evil" stop end # ... end 2.14 validates_each
This helper validates attributes against a block. It doesn't have a predefined validation function. You lot should create one using a cake, and every attribute passed to validates_each will be tested against it. In the following example, we don't want names and surnames to begin with lower case.
class Person < ApplicationRecord validates_each :name , :surname practice | record , attr , value | tape . errors . add ( attr , 'must outset with upper instance' ) if value =~ /\A[[:lower:]]/ end end The block receives the record, the aspect's name, and the attribute'southward value. You tin can do anything you like to check for valid data within the block. If your validation fails, yous should add together an error to the model, therefore making it invalid.
3 Common Validation Options
These are common validation options:
3.1 :allow_nil
The :allow_nil option skips the validation when the value beingness validated is cipher.
form Coffee < ApplicationRecord validates :size , inclusion: { in: %w(minor medium large) , bulletin: "%{value} is not a valid size" }, allow_nil: truthful terminate For full options to the bulletin argument please see the message documentation.
3.ii :allow_blank
The :allow_blank option is like to the :allow_nil option. This option will allow validation pass if the attribute's value is blank?, similar nil or an empty string for case.
class Topic < ApplicationRecord validates :title , length: { is: v }, allow_blank: true end irb> Topic . create ( title: "" ). valid? => true irb> Topic . create ( championship: zip ). valid? => truthful iii.3 :message
Every bit you've already seen, the :message option lets y'all specify the bulletin that will be added to the errors collection when validation fails. When this selection is not used, Agile Record will use the respective default error message for each validation helper. The :message option accepts a String or Proc.
A String :message value can optionally contain any/all of %{value}, %{attribute}, and %{model} which volition exist dynamically replaced when validation fails. This replacement is washed using the I18n gem, and the placeholders must match exactly, no spaces are immune.
A Proc :bulletin value is given ii arguments: the object being validated, and a hash with :model, :attribute, and :value key-value pairs.
class Person < ApplicationRecord # Difficult-coded message validates :name , presence: { message: "must be given please" } # Message with dynamic aspect value. %{value} volition be replaced # with the actual value of the attribute. %{aspect} and %{model} # are also available. validates :age , numericality: { bulletin: "%{value} seems incorrect" } # Proc validates :username , uniqueness: { # object = person object being validated # information = { model: "Person", attribute: "Username", value: <username> } bulletin: -> ( object , data ) do "Hey #{ object . name } , #{ information [ :value ] } is already taken." end } finish 3.4 :on
The :on selection lets y'all specify when the validation should happen. The default behavior for all the built-in validation helpers is to be run on salvage (both when yous're creating a new record and when you're updating information technology). If you want to alter information technology, you can use on: :create to run the validation merely when a new record is created or on: :update to run the validation simply when a tape is updated.
class Person < ApplicationRecord # it will be possible to update email with a duplicated value validates :email , uniqueness: true , on: :create # it will exist possible to create the record with a not-numerical age validates :age , numericality: true , on: :update # the default (validates on both create and update) validates :name , presence: true end You can too apply on: to define custom contexts. Custom contexts need to exist triggered explicitly by passing the name of the context to valid?, invalid?, or save.
class Person < ApplicationRecord validates :email , uniqueness: true , on: :account_setup validates :historic period , numericality: truthful , on: :account_setup end irb> person = Person . new ( age: '30-three' ) irb> person . valid? => true irb> person . valid? ( :account_setup ) => false irb> person . errors . messages => { :email => [ "has already been taken" ], :age => [ "is not a number" ]} person.valid?(:account_setup) executes both the validations without saving the model. person.salvage(context: :account_setup) validates person in the account_setup context before saving.
When triggered by an explicit context, validations are run for that context, as well as whatever validations without a context.
class Person < ApplicationRecord validates :email , uniqueness: true , on: :account_setup validates :historic period , numericality: true , on: :account_setup validates :proper noun , presence: truthful end irb> person = Person . new irb> person . valid? ( :account_setup ) => false irb> person . errors . messages => { :email => [ "has already been taken" ], :age => [ "is not a number" ], :name => [ "can't be blank" ]} 4 Strict Validations
You tin also specify validations to be strict and heighten ActiveModel::StrictValidationFailed when the object is invalid.
class Person < ApplicationRecord validates :name , presence: { strict: truthful } end irb> Person . new . valid? ActiveModel::StrictValidationFailed: Name can't be blank There is also the ability to pass a custom exception to the :strict option.
class Person < ApplicationRecord validates :token , presence: true , uniqueness: truthful , strict: TokenGenerationException end irb> Person . new . valid? TokenGenerationException: Token tin can't be blank 5 Conditional Validation
Sometimes it will brand sense to validate an object only when a given predicate is satisfied. You tin do that by using the :if and :unless options, which can take a symbol, a Proc or an Array. Y'all may use the :if pick when you desire to specify when the validation should happen. If you lot want to specify when the validation should not happen, then yous may utilise the :unless option.
5.1 Using a Symbol with :if and :unless
You can acquaintance the :if and :unless options with a symbol corresponding to the proper name of a method that will get called right before validation happens. This is the almost commonly used option.
course Club < ApplicationRecord validates :card_number , presence: true , if: :paid_with_card? def paid_with_card? payment_type == "card" end end 5.two Using a Proc with :if and :unless
It is possible to associate :if and :unless with a Proc object which volition be called. Using a Proc object gives you lot the ability to write an inline condition instead of a divide method. This choice is best suited for 1-liners.
class Business relationship < ApplicationRecord validates :password , confirmation: truthful , unless: Proc . new { | a | a . password . blank? } end As Lambdas are a blazon of Proc, they can likewise be used to write inline conditions in a shorter way.
validates :password , confirmation: true , unless: -> { password . blank? } v.3 Grouping Conditional validations
Sometimes information technology is useful to have multiple validations apply i condition. Information technology can be easily achieved using with_options.
form User < ApplicationRecord with_options if: :is_admin? exercise | admin | admin . validates :countersign , length: { minimum: 10 } admin . validates :electronic mail , presence: true end finish All validations inside of the with_options block will have automatically passed the condition if: :is_admin?
5.iv Combining Validation Conditions
On the other paw, when multiple conditions define whether or not a validation should happen, an Array can be used. Moreover, you can apply both :if and :unless to the same validation.
class Computer < ApplicationRecord validates :mouse , presence: true , if: [ Proc . new { | c | c . marketplace . retail? }, :desktop? ], unless: Proc . new { | c | c . trackpad . present? } end The validation only runs when all the :if conditions and none of the :unless weather condition are evaluated to truthful.
6 Performing Custom Validations
When the born validation helpers are not enough for your needs, you tin can write your own validators or validation methods every bit you lot adopt.
6.1 Custom Validators
Custom validators are classes that inherit from ActiveModel::Validator. These classes must implement the validate method which takes a record as an argument and performs the validation on information technology. The custom validator is called using the validates_with method.
class MyValidator < ActiveModel :: Validator def validate ( record ) unless record . proper name . start_with? 'X' record . errors . add :name , "Demand a proper name starting with 10 please!" stop end end class Person include ActiveModel :: Validations validates_with MyValidator terminate The easiest mode to add custom validators for validating individual attributes is with the convenient ActiveModel::EachValidator. In this case, the custom validator course must implement a validate_each method which takes iii arguments: record, attribute, and value. These correspond to the instance, the attribute to be validated, and the value of the attribute in the passed example.
form EmailValidator < ActiveModel :: EachValidator def validate_each ( tape , attribute , value ) unless value =~ URI :: MailTo :: EMAIL_REGEXP record . errors . add attribute , ( options [ :message ] || "is not an email" ) cease end end class Person < ApplicationRecord validates :email , presence: true , email: true finish As shown in the instance, you tin too combine standard validations with your own custom validators.
6.two Custom Methods
You tin also create methods that verify the state of your models and add errors to the errors collection when they are invalid. You lot must then register these methods by using the validate grade method, passing in the symbols for the validation methods' names.
You can pass more than ane symbol for each course method and the respective validations will exist run in the aforementioned order as they were registered.
The valid? method will verify that the errors collection is empty, so your custom validation methods should add errors to it when yous wish validation to neglect:
course Invoice < ApplicationRecord validate :expiration_date_cannot_be_in_the_past , :discount_cannot_be_greater_than_total_value def expiration_date_cannot_be_in_the_past if expiration_date . present? && expiration_date < Engagement . today errors . add ( :expiration_date , "can't exist in the past" ) cease end def discount_cannot_be_greater_than_total_value if discount > total_value errors . add together ( :disbelieve , "tin't be greater than total value" ) end end end By default, such validations will run every time you call valid? or relieve the object. But information technology is also possible to control when to run these custom validations by giving an :on choice to the validate method, with either: :create or :update.
class Invoice < ApplicationRecord validate :active_customer , on: :create def active_customer errors . add ( :customer_id , "is not active" ) unless customer . active? cease stop 7 Working with Validation Errors
The valid? and invalid? methods only provide a summary condition on validity. However you tin dig deeper into each private mistake by using various methods from the errors drove.
The post-obit is a listing of the most commonly used methods. Delight refer to the ActiveModel::Errors documentation for a listing of all the available methods.
7.1 errors
The gateway through which you tin drill down into diverse details of each error.
This returns an instance of the class ActiveModel::Errors containing all errors, each fault is represented past an ActiveModel::Error object.
class Person < ApplicationRecord validates :proper noun , presence: truthful , length: { minimum: 3 } end irb> person = Person . new irb> person . valid? => false irb> person . errors . full_messages => [ "Proper noun can't be bare" , "Proper name is also brusque (minimum is 3 characters)" ] irb> person = Person . new ( name: "John Doe" ) irb> person . valid? => truthful irb> person . errors . full_messages => [] 7.two errors[]
errors[] is used when you want to check the fault messages for a specific attribute. It returns an array of strings with all mistake messages for the given aspect, each string with ane mistake message. If there are no errors related to the attribute, it returns an empty array.
class Person < ApplicationRecord validates :proper name , presence: true , length: { minimum: 3 } end irb> person = Person . new ( name: "John Doe" ) irb> person . valid? => true irb> person . errors [ :name ] => [] irb> person = Person . new ( proper name: "JD" ) irb> person . valid? => false irb> person . errors [ :proper name ] => [ "is also curt (minimum is three characters)" ] irb> person = Person . new irb> person . valid? => false irb> person . errors [ :name ] => [ "can't be bare" , "is too short (minimum is 3 characters)" ] 7.3 errors.where and error object
Sometimes we may demand more data about each error beside its message. Each error is encapsulated every bit an ActiveModel::Error object, and where method is the near common way of admission.
where returns an assortment of mistake objects, filtered by various degree of weather condition.
grade Person < ApplicationRecord validates :name , presence: true , length: { minimum: iii } end irb> person = Person . new irb> person . valid? => imitation irb> person . errors . where ( :name ) => [ ... ] # all errors for :name aspect irb> person . errors . where ( :proper name , :too_short ) => [ ... ] # :too_short errors for :name aspect You can read various information from these fault objects:
irb> error = person . errors . where ( :proper name ). last irb> error . attribute => :name irb> error . blazon => :too_short irb> error . options [ :count ] => 3 You can also generate the error message:
irb> error . message => "is likewise curt (minimum is 3 characters)" irb> error . full_message => "Name is too brusk (minimum is iii characters)" The full_message method generates a more user-friendly message, with the capitalized aspect name prepended.
seven.4 errors.add
The add method creates the error object by taking the attribute, the fault blazon and additional options hash. This is useful for writing your own validator.
class Person < ApplicationRecord validate practise | person | errors . add together :name , :too_plain , message: "is non cool enough" cease end irb> person = Person . create irb> person . errors . where ( :name ). first . type => :too_plain irb> person . errors . where ( :name ). outset . full_message => "Name is not cool enough" 7.v errors[:base]
You can add errors that are related to the object'south state as a whole, instead of existence related to a specific attribute. You can add together errors to :base when y'all desire to say that the object is invalid, no matter the values of its attributes.
form Person < ApplicationRecord validate do | person | errors . add :base , :invalid , bulletin: "This person is invalid because ..." stop end irb> person = Person . create irb> person . errors . where ( :base of operations ). outset . full_message => "This person is invalid because ..." 7.6 errors.articulate
The articulate method is used when you intentionally want to articulate the errors collection. Of course, calling errors.clear upon an invalid object won't actually make it valid: the errors collection will now be empty, but the next time you call valid? or any method that tries to relieve this object to the database, the validations volition run once more. If whatever of the validations fail, the errors collection volition be filled again.
form Person < ApplicationRecord validates :proper name , presence: truthful , length: { minimum: 3 } end irb> person = Person . new irb> person . valid? => false irb> person . errors . empty? => simulated irb> person . errors . articulate irb> person . errors . empty? => true irb> person . save => false irb> person . errors . empty? => fake 7.7 errors.size
The size method returns the total number of errors for the object.
class Person < ApplicationRecord validates :proper name , presence: true , length: { minimum: three } finish irb> person = Person . new irb> person . valid? => simulated irb> person . errors . size => ii irb> person = Person . new ( name: "Andrea" , e-mail: "andrea@case.com" ) irb> person . valid? => true irb> person . errors . size => 0 viii Displaying Validation Errors in Views
In one case yous've created a model and added validations, if that model is created via a web course, you probably want to display an error message when one of the validations fails.
Because every application handles this kind of thing differently, Runway does not include any view helpers to help you lot generate these messages directly. However, due to the rich number of methods Rails gives you to interact with validations in general, you lot tin build your own. In addition, when generating a scaffold, Track volition put some ERB into the _form.html.erb that information technology generates that displays the full list of errors on that model.
Assuming we have a model that'southward been saved in an instance variable named @article, it looks similar this:
<% if @article . errors . any? %> <div id= "error_explanation" > <h2> <%= pluralize ( @article . errors . count , "fault" ) %> prohibited this article from being saved:</h2> <ul> <% @article . errors . each practise | mistake | %> <li> <%= fault . full_message %> </li> <% end %> </ul> </div> <% cease %> Furthermore, if you utilise the Rails form helpers to generate your forms, when a validation fault occurs on a field, it will generate an extra <div> around the entry.
<div class= "field_with_errors" > <input id= "article_title" name= "commodity[championship]" size= "30" blazon= "text" value= "" > </div> You can so mode this div however yous'd like. The default scaffold that Rails generates, for example, adds this CSS rule:
.field_with_errors { padding : 2px ; background-color : red ; display : table ; } This means that any field with an error ends up with a ii pixel red border.
Feedback
You're encouraged to help improve the quality of this guide.
Delight contribute if you come across any typos or factual errors. To get started, y'all can read our documentation contributions department.
You may also find incomplete content or stuff that is not up to date. Please do add any missing documentation for main. Make certain to check Edge Guides kickoff to verify if the issues are already stock-still or not on the principal branch. Cheque the Ruby on Runway Guides Guidelines for way and conventions.
If for whatever reason you lot spot something to fix but cannot patch information technology yourself, delight open an issue.
And last but not least, whatever kind of give-and-take regarding Crimson on Rails documentation is very welcome on the rubyonrails-docs mailing list.
Source: https://edgeguides.rubyonrails.org/active_record_validations.html
0 Response to "Rails Validation Check Again Null and Blank"
Post a Comment