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method

validates_presence_of

Importance_3
v2.3.2 - Show latest stable - 3 notes - Class: ActiveModel::Validations::ClassMethods
validates_presence_of(*attr_names) public

Validates that the specified attributes are not blank (as defined by Object#blank?). Happens by default on save. Example:

  class Person < ActiveRecord::Base
    validates_presence_of :first_name
  end

The first_name attribute must be in the object and it cannot be blank.

If you want to validate the presence of a boolean field (where the real values are true and false), you will want to use

  validates_inclusion_of :field_name, :in => [true, false]

This is due to the way Object#blank? handles boolean values:

  false.blank? # => true

Configuration options:

  • :message - A custom error message (default is: "can’t be blank")
  • :on - Specifies when this validation is active (default is :save, other options :create, :update)
  • :if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. :if => :allow_validation, or :if => Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.
  • :unless - Specifies a method, proc or string to call to determine if the validation should not occur (e.g. :unless => :skip_validation, or :unless => Proc.new { |user| user.signup_step <= 2 }). The method, proc or string should return or evaluate to a true or false value.
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March 23, 2011 - (v3.0.0 - v3.0.5)
1 thank
January 21, 2011 - (<= v2.3.8)
0 thanks

Doesn't work for associations.

This method relies on #blank? to determine if the attribute is valid.

When you call #blank? on an ActiveRecord object, it returns true as long as there are no changes to the object.

So you can validate the base attribute (i.e.: product_id), but you’ll have no guarantee that it points to a valid record without your own validator.

March 23, 2011 - (v3.0.0 - v3.0.5)
0 thanks