ActiveModel::AttributeMethods::ClassMethods

Declares a method available for all attributes with the given prefix and suffix. Uses method_missing and respond_to? to rewrite the method.

  #{prefix}#{attr}#{suffix}(*args, &block)

to

  #{prefix}attribute#{suffix}(#{attr}, *args, &block)

An #{prefix}attribute#{suffix} instance method must exist and accept at least the attr argument.

For example:

  class Person

    include ActiveModel::AttributeMethods
    attr_accessor :name
    attribute_method_affix :prefix => 'reset_', :suffix => '_to_default!'
    define_attribute_methods [:name]

    private

    def reset_attribute_to_default!(attr)
      ...
    end
  end

  person = Person.new
  person.name                         # => 'Gem'
  person.reset_name_to_default!
  person.name                         # => 'Gemma'

     # File lib/active_model/attribute_methods.rb, line 220
220:       def attribute_method_affix(*affixes)
221:         attribute_method_matchers.concat(affixes.map { |affix| AttributeMethodMatcher.new :prefix => affix[:prefix], :suffix => affix[:suffix] })
222:         undefine_attribute_methods
223:       end

Declares a method available for all attributes with the given prefix. Uses method_missing and respond_to? to rewrite the method.

  #{prefix}#{attr}(*args, &block)

to

  #{prefix}attribute(#{attr}, *args, &block)

An instance method #{prefix}attribute must exist and accept at least the attr argument.

For example:

  class Person

    include ActiveModel::AttributeMethods
    attr_accessor :name
    attribute_method_prefix 'clear_'
    define_attribute_methods [:name]

    private

    def clear_attribute(attr)
      send("#{attr}=", nil)
    end
  end

  person = Person.new
  person.name = "Bob"
  person.name          # => "Bob"
  person.clear_name
  person.name          # => nil

     # File lib/active_model/attribute_methods.rb, line 145
145:       def attribute_method_prefix(*prefixes)
146:         attribute_method_matchers.concat(prefixes.map { |prefix| AttributeMethodMatcher.new :prefix => prefix })
147:         undefine_attribute_methods
148:       end

Declares a method available for all attributes with the given suffix. Uses method_missing and respond_to? to rewrite the method.

  #{attr}#{suffix}(*args, &block)

to

  attribute#{suffix}(#{attr}, *args, &block)

An attribute#{suffix} instance method must exist and accept at least the attr argument.

For example:

  class Person

    include ActiveModel::AttributeMethods
    attr_accessor :name
    attribute_method_suffix '_short?'
    define_attribute_methods [:name]

    private

    def attribute_short?(attr)
      send(attr).length < 5
    end
  end

  person = Person.new
  person.name = "Bob"
  person.name          # => "Bob"
  person.name_short?   # => true

     # File lib/active_model/attribute_methods.rb, line 182
182:       def attribute_method_suffix(*suffixes)
183:         attribute_method_matchers.concat(suffixes.map { |suffix| AttributeMethodMatcher.new :suffix => suffix })
184:         undefine_attribute_methods
185:       end

Returns true if the attribute methods defined have been generated.

     # File lib/active_model/attribute_methods.rb, line 304
304:       def attribute_methods_generated?
305:         @attribute_methods_generated ||= nil
306:       end

Defines an “attribute” method (like inheritance_column or table_name). A new (class) method will be created with the given name. If a value is specified, the new method will return that value (as a string). Otherwise, the given block will be used to compute the value of the method.

The original method will be aliased, with the new name being prefixed with “original_”. This allows the new method to access the original value.

Example:

  class Person

    include ActiveModel::AttributeMethods

    cattr_accessor :primary_key
    cattr_accessor :inheritance_column

    define_attr_method :primary_key, "sysid"
    define_attr_method( :inheritance_column ) do
      original_inheritance_column + "_id"
    end

  end

Provides you with:

  AttributePerson.primary_key
  # => "sysid"
  AttributePerson.inheritance_column = 'address'
  AttributePerson.inheritance_column
  # => 'address_id'

     # File lib/active_model/attribute_methods.rb, line 93
 93:       def define_attr_method(name, value=nil, &block)
 94:         sing = singleton_class
 95:         sing.class_eval           if method_defined?(:original_#{name})            undef :original_#{name}          end          alias_method :original_#{name}, :#{name}, __FILE__, __LINE__ + 1
 96:         if block_given?
 97:           sing.send :define_method, name, &block
 98:         else
 99:           # use eval instead of a block to work around a memory leak in dev
100:           # mode in fcgi
101:           sing.class_eval             def #{name}; #{value.to_s.inspect}; end, __FILE__, __LINE__ + 1
102:         end
103:       end

Declares a the attributes that should be prefixed and suffixed by ActiveModel::AttributeMethods.

To use, pass in an array of attribute names (as strings or symbols), be sure to declare define_attribute_methods after you define any prefix, suffix or affix methods, or they will not hook in.

  class Person

    include ActiveModel::AttributeMethods
    attr_accessor :name, :age, :address
    attribute_method_prefix 'clear_'

    # Call to define_attribute_methods must appear after the
    # attribute_method_prefix, attribute_method_suffix or
    # attribute_method_affix declares.
    define_attribute_methods [:name, :age, :address]

    private

    def clear_attribute(attr)
      ...
    end
  end

     # File lib/active_model/attribute_methods.rb, line 259
259:       def define_attribute_methods(attr_names)
260:         return if attribute_methods_generated?
261:         attr_names.each do |attr_name|
262:           attribute_method_matchers.each do |matcher|
263:             unless instance_method_already_implemented?(matcher.method_name(attr_name))
264:               generate_method = "define_method_#{matcher.prefix}attribute#{matcher.suffix}"
265: 
266:               if respond_to?(generate_method)
267:                 send(generate_method, attr_name)
268:               else
269:                 method_name = matcher.method_name(attr_name)
270: 
271:                 generated_attribute_methods.module_eval                   if method_defined?(:#{method_name})                    undef :#{method_name}                  end                  def #{method_name}(*args)                    send(:#{matcher.method_missing_target}, '#{attr_name}', *args)                  end, __FILE__, __LINE__ + 1
272:               end
273:             end
274:           end
275:         end
276:         @attribute_methods_generated = true
277:       end

Removes all the previously dynamically defined methods from the class

     # File lib/active_model/attribute_methods.rb, line 287
287:       def undefine_attribute_methods
288:         generated_attribute_methods.module_eval do
289:           instance_methods.each { |m| undef_method(m) }
290:         end
291:         @attribute_methods_generated = nil
292:       end