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411 lines
14 KiB
Ruby
411 lines
14 KiB
Ruby
require 'active_support/core_ext/hash/keys'
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require 'active_support/core_ext/class/attribute'
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module ActiveModel
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class MissingAttributeError < NoMethodError
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end
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# == Active Model Attribute Methods
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#
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# <tt>ActiveModel::AttributeMethods</tt> provides a way to add prefixes and suffixes
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# to your methods as well as handling the creation of Active Record like class methods
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# such as +table_name+.
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#
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# The requirements to implement ActiveModel::AttributeMethods are to:
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#
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# * <tt>include ActiveModel::AttributeMethods</tt> in your object
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# * Call each Attribute Method module method you want to add, such as
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# attribute_method_suffix or attribute_method_prefix
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# * Call <tt>define_attribute_methods</tt> after the other methods are
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# called.
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# * Define the various generic +_attribute+ methods that you have declared
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#
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# A minimal implementation could be:
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#
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# class Person
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# include ActiveModel::AttributeMethods
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#
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# attribute_method_affix :prefix => 'reset_', :suffix => '_to_default!'
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# attribute_method_suffix '_contrived?'
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# attribute_method_prefix 'clear_'
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# define_attribute_methods ['name']
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#
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# attr_accessor :name
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#
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# private
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#
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# def attribute_contrived?(attr)
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# true
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# end
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#
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# def clear_attribute(attr)
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# send("#{attr}=", nil)
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# end
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#
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# def reset_attribute_to_default!(attr)
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# send("#{attr}=", "Default Name")
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# end
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# end
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#
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# Notice that whenever you include ActiveModel::AttributeMethods in your class,
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# it requires you to implement a <tt>attributes</tt> methods which returns a hash
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# with each attribute name in your model as hash key and the attribute value as
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# hash value.
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#
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# Hash keys must be strings.
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#
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module AttributeMethods
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extend ActiveSupport::Concern
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included do
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class_attribute :attribute_method_matchers, :instance_writer => false
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self.attribute_method_matchers = []
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end
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module ClassMethods
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# Defines an "attribute" method (like +inheritance_column+ or +table_name+).
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# A new (class) method will be created with the given name. If a value is
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# specified, the new method will return that value (as a string).
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# Otherwise, the given block will be used to compute the value of the
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# method.
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#
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# The original method will be aliased, with the new name being prefixed
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# with "original_". This allows the new method to access the original
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# value.
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#
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# Example:
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#
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# class Person
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#
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# include ActiveModel::AttributeMethods
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#
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# cattr_accessor :primary_key
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# cattr_accessor :inheritance_column
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#
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# define_attr_method :primary_key, "sysid"
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# define_attr_method( :inheritance_column ) do
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# original_inheritance_column + "_id"
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# end
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#
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# end
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#
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# Provides you with:
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#
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# AttributePerson.primary_key
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# # => "sysid"
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# AttributePerson.inheritance_column = 'address'
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# AttributePerson.inheritance_column
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# # => 'address_id'
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def define_attr_method(name, value=nil, &block)
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sing = singleton_class
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sing.class_eval <<-eorb, __FILE__, __LINE__ + 1
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if method_defined?(:original_#{name})
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undef :original_#{name}
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end
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alias_method :original_#{name}, :#{name}
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eorb
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if block_given?
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sing.send :define_method, name, &block
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else
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# use eval instead of a block to work around a memory leak in dev
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# mode in fcgi
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sing.class_eval <<-eorb, __FILE__, __LINE__ + 1
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def #{name}; #{value.to_s.inspect}; end
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eorb
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end
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end
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# Declares a method available for all attributes with the given prefix.
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# Uses +method_missing+ and <tt>respond_to?</tt> to rewrite the method.
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#
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# #{prefix}#{attr}(*args, &block)
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#
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# to
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#
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# #{prefix}attribute(#{attr}, *args, &block)
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#
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# An instance method <tt>#{prefix}attribute</tt> must exist and accept
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# at least the +attr+ argument.
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#
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# For example:
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#
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# class Person
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#
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# include ActiveModel::AttributeMethods
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# attr_accessor :name
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# attribute_method_prefix 'clear_'
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# define_attribute_methods [:name]
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#
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# private
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#
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# def clear_attribute(attr)
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# send("#{attr}=", nil)
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# end
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# end
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#
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# person = Person.new
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# person.name = "Bob"
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# person.name # => "Bob"
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# person.clear_name
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# person.name # => nil
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def attribute_method_prefix(*prefixes)
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self.attribute_method_matchers += prefixes.map { |prefix| AttributeMethodMatcher.new :prefix => prefix }
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undefine_attribute_methods
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end
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# Declares a method available for all attributes with the given suffix.
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# Uses +method_missing+ and <tt>respond_to?</tt> to rewrite the method.
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#
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# #{attr}#{suffix}(*args, &block)
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#
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# to
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#
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# attribute#{suffix}(#{attr}, *args, &block)
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#
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# An <tt>attribute#{suffix}</tt> instance method must exist and accept at least
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# the +attr+ argument.
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#
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# For example:
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#
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# class Person
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#
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# include ActiveModel::AttributeMethods
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# attr_accessor :name
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# attribute_method_suffix '_short?'
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# define_attribute_methods [:name]
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#
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# private
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#
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# def attribute_short?(attr)
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# send(attr).length < 5
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# end
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# end
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#
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# person = Person.new
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# person.name = "Bob"
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# person.name # => "Bob"
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# person.name_short? # => true
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def attribute_method_suffix(*suffixes)
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self.attribute_method_matchers += suffixes.map { |suffix| AttributeMethodMatcher.new :suffix => suffix }
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undefine_attribute_methods
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end
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# Declares a method available for all attributes with the given prefix
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# and suffix. Uses +method_missing+ and <tt>respond_to?</tt> to rewrite
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# the method.
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#
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# #{prefix}#{attr}#{suffix}(*args, &block)
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#
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# to
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#
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# #{prefix}attribute#{suffix}(#{attr}, *args, &block)
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#
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# An <tt>#{prefix}attribute#{suffix}</tt> instance method must exist and
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# accept at least the +attr+ argument.
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#
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# For example:
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#
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# class Person
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#
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# include ActiveModel::AttributeMethods
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# attr_accessor :name
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# attribute_method_affix :prefix => 'reset_', :suffix => '_to_default!'
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# define_attribute_methods [:name]
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#
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# private
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#
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# def reset_attribute_to_default!(attr)
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# ...
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# end
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# end
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#
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# person = Person.new
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# person.name # => 'Gem'
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# person.reset_name_to_default!
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# person.name # => 'Gemma'
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def attribute_method_affix(*affixes)
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self.attribute_method_matchers += affixes.map { |affix| AttributeMethodMatcher.new :prefix => affix[:prefix], :suffix => affix[:suffix] }
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undefine_attribute_methods
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end
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def alias_attribute(new_name, old_name)
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attribute_method_matchers.each do |matcher|
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module_eval <<-STR, __FILE__, __LINE__ + 1
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def #{matcher.method_name(new_name)}(*args)
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send(:#{matcher.method_name(old_name)}, *args)
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end
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STR
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end
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end
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# Declares a the attributes that should be prefixed and suffixed by
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# ActiveModel::AttributeMethods.
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#
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# To use, pass in an array of attribute names (as strings or symbols),
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# be sure to declare +define_attribute_methods+ after you define any
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# prefix, suffix or affix methods, or they will not hook in.
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#
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# class Person
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#
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# include ActiveModel::AttributeMethods
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# attr_accessor :name, :age, :address
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# attribute_method_prefix 'clear_'
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#
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# # Call to define_attribute_methods must appear after the
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# # attribute_method_prefix, attribute_method_suffix or
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# # attribute_method_affix declares.
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# define_attribute_methods [:name, :age, :address]
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#
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# private
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#
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# def clear_attribute(attr)
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# ...
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# end
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# end
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def define_attribute_methods(attr_names)
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return if attribute_methods_generated?
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attr_names.each do |attr_name|
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attribute_method_matchers.each do |matcher|
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unless instance_method_already_implemented?(matcher.method_name(attr_name))
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generate_method = "define_method_#{matcher.prefix}attribute#{matcher.suffix}"
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if respond_to?(generate_method)
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send(generate_method, attr_name)
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else
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method_name = matcher.method_name(attr_name)
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generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1
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if method_defined?(:#{method_name})
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undef :#{method_name}
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end
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def #{method_name}(*args)
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send(:#{matcher.method_missing_target}, '#{attr_name}', *args)
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end
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STR
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end
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end
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end
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end
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@attribute_methods_generated = true
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end
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# Removes all the previously dynamically defined methods from the class
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def undefine_attribute_methods
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generated_attribute_methods.module_eval do
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instance_methods.each { |m| undef_method(m) }
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end
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@attribute_methods_generated = nil
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end
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# Returns true if the attribute methods defined have been generated.
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def generated_attribute_methods #:nodoc:
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@generated_attribute_methods ||= begin
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mod = Module.new
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include mod
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mod
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end
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end
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# Returns true if the attribute methods defined have been generated.
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def attribute_methods_generated?
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@attribute_methods_generated ||= nil
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end
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protected
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def instance_method_already_implemented?(method_name)
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method_defined?(method_name)
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end
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private
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class AttributeMethodMatcher
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attr_reader :prefix, :suffix, :method_missing_target
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AttributeMethodMatch = Struct.new(:target, :attr_name)
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def initialize(options = {})
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options.symbolize_keys!
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@prefix, @suffix = options[:prefix] || '', options[:suffix] || ''
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@regex = /^(#{Regexp.escape(@prefix)})(.+?)(#{Regexp.escape(@suffix)})$/
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@method_missing_target = :"#{@prefix}attribute#{@suffix}"
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@method_name = "#{prefix}%s#{suffix}"
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end
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def match(method_name)
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if @regex =~ method_name
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AttributeMethodMatch.new(method_missing_target, $2)
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else
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nil
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end
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end
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def method_name(attr_name)
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@method_name % attr_name
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end
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end
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end
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# Allows access to the object attributes, which are held in the
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# <tt>@attributes</tt> hash, as though they were first-class methods. So a
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# Person class with a name attribute can use Person#name and Person#name=
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# and never directly use the attributes hash -- except for multiple assigns
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# with ActiveRecord#attributes=. A Milestone class can also ask
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# Milestone#completed? to test that the completed attribute is not +nil+
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# or 0.
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#
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# It's also possible to instantiate related objects, so a Client class
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# belonging to the clients table with a +master_id+ foreign key can
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# instantiate master through Client#master.
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def method_missing(method_id, *args, &block)
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method_name = method_id.to_s
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if match = match_attribute_method?(method_name)
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guard_private_attribute_method!(method_name, args)
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return __send__(match.target, match.attr_name, *args, &block)
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end
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super
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end
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# A Person object with a name attribute can ask <tt>person.respond_to?(:name)</tt>,
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# <tt>person.respond_to?(:name=)</tt>, and <tt>person.respond_to?(:name?)</tt>
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# which will all return +true+.
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alias :respond_to_without_attributes? :respond_to?
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def respond_to?(method, include_private_methods = false)
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if super
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return true
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elsif !include_private_methods && super(method, true)
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# If we're here then we haven't found among non-private methods
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# but found among all methods. Which means that the given method is private.
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return false
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elsif match_attribute_method?(method.to_s)
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return true
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end
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super
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end
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protected
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def attribute_method?(attr_name)
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attributes.include?(attr_name)
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end
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private
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# Returns a struct representing the matching attribute method.
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# The struct's attributes are prefix, base and suffix.
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def match_attribute_method?(method_name)
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self.class.attribute_method_matchers.each do |method|
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if (match = method.match(method_name)) && attribute_method?(match.attr_name)
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return match
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end
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end
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nil
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end
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# prevent method_missing from calling private methods with #send
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def guard_private_attribute_method!(method_name, args)
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if self.class.private_method_defined?(method_name)
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raise NoMethodError.new("Attempt to call private method `#{method_name}'", method_name, args)
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end
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end
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def missing_attribute(attr_name, stack)
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raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack
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end
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end
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end
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