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[RW] | attr_internal_naming_format |
Allows you to make aliases for attributes, which includes getter, setter, and query methods.
Example:
class Content < ActiveRecord::Base # has a title attribute end class Email < Content alias_attribute :subject, :title end e = Email.find(1) e.title # => "Superstars" e.subject # => "Superstars" e.subject? # => true e.subject = "Megastars" e.title # => "Megastars"
Source: show
# File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 63 def alias_attribute(new_name, old_name) module_eval " def #{new_name}; self.#{old_name}; end # def subject; self.title; end def #{new_name}?; self.#{old_name}?; end # def subject?; self.title?; end def #{new_name}=(v); self.#{old_name} = v; end # def subject=(v); self.title = v; end ", __FILE__, __LINE__ + 1 end
Encapsulates the common pattern of:
alias_method :foo_without_feature, :foo alias_method :foo, :foo_with_feature
With this, you simply do:
alias_method_chain :foo, :feature
And both aliases are set up for you.
Query and bang methods (foo?, foo!) keep the same punctuation:
alias_method_chain :foo?, :feature
is equivalent to
alias_method :foo_without_feature?, :foo? alias_method :foo?, :foo_with_feature?
so you can safely chain foo, foo?, and foo! with the same feature.
Source: show
# File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 23 def alias_method_chain(target, feature) # Strip out punctuation on predicates or bang methods since # e.g. target?_without_feature is not a valid method name. aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1 yield(aliased_target, punctuation) if block_given? with_method, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}" alias_method without_method, target alias_method target, with_method case when public_method_defined?(without_method) public target when protected_method_defined?(without_method) protected target when private_method_defined?(without_method) private target end end
A module may or may not have a name.
module M; end M.name # => "M" m = Module.new m.name # => ""
A module gets a name when it is first assigned to a constant. Either via
the module
or class
keyword or by an explicit
assignment:
m = Module.new # creates an anonymous module M = m # => m gets a name here as a side-effect m.name # => "M"
Source: show
# File activesupport/lib/active_support/core_ext/module/anonymous.rb, line 19 def anonymous? # Uses blank? because the name of an anonymous class is an empty # string in 1.8, and nil in 1.9. name.blank? end
Declare an attribute accessor with an initial default return value.
To give attribute :age
the initial value 25
:
class Person attr_accessor_with_default :age, 25 end person = Person.new person.age # => 25 person.age = 26 person.age # => 26
To give attribute :element_name
a dynamic default value,
evaluated in scope of self:
attr_accessor_with_default(:element_name) { name.underscore }
Source: show
# File activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb, line 21 def attr_accessor_with_default(sym, default = Proc.new) ActiveSupport::Deprecation.warn "attr_accessor_with_default is deprecated. Use Ruby instead!" define_method(sym, block_given? ? default : Proc.new { default }) module_eval(" def #{sym}=(value) # def age=(value) class << self; attr_accessor :#{sym} end # class << self; attr_accessor :age end @#{sym} = value # @age = value end # end ", __FILE__, __LINE__ + 1) end
Declares an attribute reader and writer backed by an internally-named instance variable.
Source: show
# File activesupport/lib/active_support/core_ext/module/attr_internal.rb, line 14 def attr_internal_accessor(*attrs) attr_internal_reader(*attrs) attr_internal_writer(*attrs) end
Declares an attribute reader backed by an internally-named instance variable.
Source: show
# File activesupport/lib/active_support/core_ext/module/attr_internal.rb, line 3 def attr_internal_reader(*attrs) attrs.each {|attr_name| attr_internal_define(attr_name, :reader)} end
Declares an attribute writer backed by an internally-named instance variable.
Source: show
# File activesupport/lib/active_support/core_ext/module/attr_internal.rb, line 8 def attr_internal_writer(*attrs) attrs.each {|attr_name| attr_internal_define(attr_name, :writer)} end
Provides a delegate class method to easily expose contained objects’
methods as your own. Pass one or more methods (specified as symbols or
strings) and the name of the target object via the :to
option
(also a symbol or string). At least one method and the :to
option are required.
Delegation is particularly useful with Active Record associations:
class Greeter < ActiveRecord::Base def hello "hello" end def goodbye "goodbye" end end class Foo < ActiveRecord::Base belongs_to :greeter delegate :hello, :to => :greeter end Foo.new.hello # => "hello" Foo.new.goodbye # => NoMethodError: undefined method `goodbye' for #<Foo:0x1af30c>
Multiple delegates to the same target are allowed:
class Foo < ActiveRecord::Base belongs_to :greeter delegate :hello, :goodbye, :to => :greeter end Foo.new.goodbye # => "goodbye"
Methods can be delegated to instance variables, class variables, or constants by providing them as a symbols:
class Foo CONSTANT_ARRAY = [0,1,2,3] @@class_array = [4,5,6,7] def initialize @instance_array = [8,9,10,11] end delegate :sum, :to => :CONSTANT_ARRAY delegate :min, :to => :@@class_array delegate :max, :to => :@instance_array end Foo.new.sum # => 6 Foo.new.min # => 4 Foo.new.max # => 11
Delegates can optionally be prefixed using the :prefix
option.
If the value is true
, the delegate methods are prefixed with
the name of the object being delegated to.
Person = Struct.new(:name, :address) class Invoice < Struct.new(:client) delegate :name, :address, :to => :client, :prefix => true end john_doe = Person.new("John Doe", "Vimmersvej 13") invoice = Invoice.new(john_doe) invoice.client_name # => "John Doe" invoice.client_address # => "Vimmersvej 13"
It is also possible to supply a custom prefix.
class Invoice < Struct.new(:client) delegate :name, :address, :to => :client, :prefix => :customer end invoice = Invoice.new(john_doe) invoice.customer_name # => "John Doe" invoice.customer_address # => "Vimmersvej 13"
If the delegate object is nil
an exception is raised, and that
happens no matter whether nil
responds to the delegated
method. You can get a nil
instead with the
:allow_nil
option.
class Foo attr_accessor :bar def initialize(bar = nil) @bar = bar end delegate :zoo, :to => :bar end Foo.new.zoo # raises NoMethodError exception (you called nil.zoo) class Foo attr_accessor :bar def initialize(bar = nil) @bar = bar end delegate :zoo, :to => :bar, :allow_nil => true end Foo.new.zoo # returns nil
Source: show
# File activesupport/lib/active_support/core_ext/module/delegation.rb, line 106 def delegate(*methods) options = methods.pop unless options.is_a?(Hash) && to = options[:to] raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)." end if options[:prefix] == true && options[:to].to_s =~ /^[^a-z_]/ raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method." end prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_" || '' file, line = caller.first.split(':', 2) line = line.to_i methods.each do |method| on_nil = if options[:allow_nil] 'return' else %Q(raise "#{self}##{prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}") end module_eval(" def #{prefix}#{method}(*args, &block) # def customer_name(*args, &block) #{to}.__send__(#{method.inspect}, *args, &block) # client.__send__(:name, *args, &block) rescue NoMethodError # rescue NoMethodError if #{to}.nil? # if client.nil? #{on_nil} # return # depends on :allow_nil else # else raise # raise end # end end # end ", file, line - 1) end end
Declare that a method has been deprecated.
deprecate :foo deprecate :bar => 'message' deprecate :foo, :bar, :baz => 'warning!', :qux => 'gone!'
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# File activesupport/lib/active_support/core_ext/module/deprecation.rb, line 6 def deprecate(*method_names) ActiveSupport::Deprecation.deprecate_methods(self, *method_names) end
Modules are not duplicable:
m = Module.new # => #<Module:0x10328b6e0> m.dup # => #<Module:0x10328b6e0>
Note dup
returned the same module object.
Source: show
# File activesupport/lib/active_support/core_ext/object/duplicable.rb, line 103 def duplicable? false end
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# File activesupport/lib/active_support/core_ext/module/method_names.rb, line 3 def instance_method_names(*args) instance_methods(*args).map(&:to_s) end
Returns the names of the constants defined locally rather than the
constants themselves. See local_constants
.
Source: show
# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 85 def local_constant_names local_constants.map { |c| c.to_s } end
Returns the constants that have been defined locally by this object and not in an ancestor. This method is exact if running under Ruby 1.9. In previous versions it may miss some constants if their definition in some ancestor is identical to their definition in the receiver.
Source: show
# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 65 def local_constants inherited = {} ancestors.each do |anc| next if anc == self anc.constants.each { |const| inherited[const] = anc.const_get(const) } end constants.select do |const| !inherited.key?(const) || inherited[const].object_id != const_get(const).object_id end end
Extends the module object with module and instance accessors for class attributes, just like the native attr* accessors for instance attributes.
module AppConfiguration mattr_accessor :google_api_key self.google_api_key = "123456789" mattr_accessor :paypal_url self.paypal_url = "www.sandbox.paypal.com" end AppConfiguration.google_api_key = "overriding the api key!"
Source: show
# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 56 def mattr_accessor(*syms) mattr_reader(*syms) mattr_writer(*syms) end
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# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 4 def mattr_reader(*syms) options = syms.extract_options! syms.each do |sym| class_eval(" @@#{sym} = nil unless defined? @@#{sym} def self.#{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) unless options[:instance_reader] == false class_eval(" def #{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) end end end
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# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 25 def mattr_writer(*syms) options = syms.extract_options! syms.each do |sym| class_eval(" def self.#{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) unless options[:instance_writer] == false class_eval(" def #{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) end end end
Source: show
# File activesupport/lib/active_support/core_ext/module/method_names.rb, line 7 def method_names(*args) methods(*args).map(&:to_s) end
Returns the module which contains this one according to its name.
module M module N end end X = M::N M::N.parent # => M X.parent # => M
The parent of top-level and anonymous modules is Object.
M.parent # => Object Module.new.parent # => Object
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# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 30 def parent parent_name ? ActiveSupport::Inflector.constantize(parent_name) : Object end
Returns the name of the module containing this one.
M::N.parent_name # => "M"
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# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 7 def parent_name unless defined? @parent_name @parent_name = name =~ /::[^:]+\Z/ ? $`.freeze : nil end @parent_name end
Returns all the parents of this module according to its name, ordered from nested outwards. The receiver is not contained within the result.
module M module N end end X = M::N M.parents # => [Object] M::N.parents # => [M, Object] X.parents # => [M, Object]
Source: show
# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 47 def parents parents = [] if parent_name parts = parent_name.split('::') until parts.empty? parents << ActiveSupport::Inflector.constantize(parts * '::') parts.pop end end parents << Object unless parents.include? Object parents end
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# File activesupport/lib/active_support/core_ext/module/remove_method.rb, line 12 def redefine_method(method, &block) remove_possible_method(method) define_method(method, &block) end
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# File activesupport/lib/active_support/core_ext/module/remove_method.rb, line 2 def remove_possible_method(method) if method_defined?(method) || private_method_defined?(method) remove_method(method) end rescue NameError # If the requested method is defined on a superclass or included module, # method_defined? returns true but remove_method throws a NameError. # Ignore this. end
Synchronize access around a method, delegating synchronization to a particular mutex. A mutex (either a Mutex, or any object that responds to #synchronize and yields to a block) must be provided as a final :with option. The :with option should be a symbol or string, and can represent a method, constant, or instance or class variable. Example:
class SharedCache @@lock = Mutex.new def expire ... end synchronize :expire, :with => :@@lock end
Source: show
# File activesupport/lib/active_support/core_ext/module/synchronization.rb, line 19 def synchronize(*methods) options = methods.extract_options! unless options.is_a?(Hash) && with = options[:with] raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)." end methods.each do |method| aliased_method, punctuation = method.to_s.sub(/([?!=])$/, ''), $1 if method_defined?("#{aliased_method}_without_synchronization#{punctuation}") raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported." end module_eval(" def #{aliased_method}_with_synchronization#{punctuation}(*args, &block) # def expire_with_synchronization(*args, &block) #{with}.synchronize do # @@lock.synchronize do #{aliased_method}_without_synchronization#{punctuation}(*args, &block) # expire_without_synchronization(*args, &block) end # end end # end ", __FILE__, __LINE__ + 1) alias_method_chain method, :synchronization end end