Methods

Instance Public methods

attribute_method?(attribute)

Returns true if attribute is an attribute method and table exists, false otherwise.

class Person < ActiveRecord::Base
end

Person.attribute_method?('name')   # => true
Person.attribute_method?(:age=)    # => true
Person.attribute_method?(:nothing) # => false
📝 Source code 
# File activerecord/lib/active_record/attribute_methods.rb, line 150
      def attribute_method?(attribute)
        super || (table_exists? && column_names.include?(attribute.to_s.delete_suffix("=")))
      end
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attribute_names()

Returns an array of column names as strings if it's not an abstract class and table exists. Otherwise it returns an empty array.

class Person < ActiveRecord::Base
end

Person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]
📝 Source code 
# File activerecord/lib/active_record/attribute_methods.rb, line 162
      def attribute_names
        @attribute_names ||= if !abstract_class? && table_exists?
          attribute_types.keys
        else
          []
        end.freeze
      end
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dangerous_class_method?(method_name)

A class method is 'dangerous' if it is already (re)defined by Active Record, but not by any ancestors. (So 'puts' is not dangerous but 'new' is.)

📝 Source code 
# File activerecord/lib/active_record/attribute_methods.rb, line 127
      def dangerous_class_method?(method_name)
        return true if RESTRICTED_CLASS_METHODS.include?(method_name.to_s)

        if Base.respond_to?(method_name, true)
          if Object.respond_to?(method_name, true)
            Base.method(method_name).owner != Object.method(method_name).owner
          else
            true
          end
        else
          false
        end
      end
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has_attribute?(attr_name)

Returns true if the given attribute exists, otherwise false.

class Person < ActiveRecord::Base
  alias_attribute :new_name, :name
end

Person.has_attribute?('name')     # => true
Person.has_attribute?('new_name') # => true
Person.has_attribute?(:age)       # => true
Person.has_attribute?(:nothing)   # => false
📝 Source code 
# File activerecord/lib/active_record/attribute_methods.rb, line 180
      def has_attribute?(attr_name)
        attr_name = attr_name.to_s
        attr_name = attribute_aliases[attr_name] || attr_name
        attribute_types.key?(attr_name)
      end
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instance_method_already_implemented?(method_name)

Raises an ActiveRecord::DangerousAttributeError exception when an Active Record method is defined in the model, otherwise false.

class Person < ActiveRecord::Base
  def save
    'already defined by Active Record'
  end
end

Person.instance_method_already_implemented?(:save)
# => ActiveRecord::DangerousAttributeError: save is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name.

Person.instance_method_already_implemented?(:name)
# => false
📝 Source code 
# File activerecord/lib/active_record/attribute_methods.rb, line 91
      def instance_method_already_implemented?(method_name)
        if dangerous_attribute_method?(method_name)
          raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name."
        end

        if superclass == Base
          super
        else
          # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass
          # defines its own attribute method, then we don't want to overwrite that.
          defined = method_defined_within?(method_name, superclass, Base) &&
            ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods)
          defined || super
        end
      end
🔎 See on GitHub