module ActiveRecord::AttributeMethods::ClassMethods - activerecord-4.2.5.2 Documentation

# module ActiveRecord::AttributeMethods::ClassMethods

### Public Instance Methods

attribute_method?(attribute) click to toggle source

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

Calls superclass method

    # File lib/active_record/attribute_methods.rb, line 174
    def attribute_method?(attribute)
      super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
    end

attribute_names() click to toggle source

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"]

    # File lib/active_record/attribute_methods.rb, line 186
    def attribute_names
      @attribute_names ||= if !abstract_class? && table_exists?
          column_names
        else
          []
        end
    end

class_method_defined_within?(name, klass, superklass = klass.superclass) click to toggle source

    # File lib/active_record/attribute_methods.rb, line 153
    def class_method_defined_within?(name, klass, superklass = klass.superclass) # :nodoc
      if klass.respond_to?(name, true)
        if superklass.respond_to?(name, true)
          klass.method(name).owner != superklass.method(name).owner
        else
          true
        end
      else
        false
      end
    end

column_for_attribute(name) click to toggle source

Returns the column object for the named attribute. Returns nil if the named attribute does not exist.

    class Person < ActiveRecord::Base
    end

    person = Person.new
    person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
    # => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

    person.column_for_attribute(:nothing)
    # => nil

    # File lib/active_record/attribute_methods.rb, line 206
          def column_for_attribute(name)
            column = columns_hash[name.to_s]
            if column.nil?
              ActiveSupport::Deprecation.warn("            `#column_for_attribute` will return a null object for non-existent
                columns in Rails 5. Use `#has_attribute?` if you need to check for
                an attribute's existence.
    ".squish)
            end
            column
          end

dangerous_class_method?(method_name) click to toggle source

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.)

    # File lib/active_record/attribute_methods.rb, line 149
    def dangerous_class_method?(method_name)
      BLACKLISTED_CLASS_METHODS.include?(method_name.to_s) || class_method_defined_within?(method_name, Base)
    end

instance_method_already_implemented?(method_name) click to toggle source

Raises a `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 ActiveRecord

    Person.instance_method_already_implemented?(:name)
    # => false

Calls superclass method

    # File lib/active_record/attribute_methods.rb, line 113
    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