Extends the API for constants to be able to deal with qualified names. Arguments are assumed to be relative to the receiver.
- A
- D
- L
- M
- P
- Q
- R
| [RW] | attr_internal_naming_format |
Allows you to make aliases for attributes, which includes getter, setter, and query methods.
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"
# File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 62 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.
# 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 = "#{aliased_target}_with_#{feature}#{punctuation}" without_method = "#{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 # => nil
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"
Declares an attribute reader and writer backed by an internally-named instance variable.
Declares an attribute reader backed by an internally-named instance variable.
Declares an attribute writer backed by an internally-named instance variable.
Provides a delegate class method to easily expose contained
objects' public methods as your own.
The macro receives one or more method names (specified as symbols or
strings) and the name of the target object via the :to option
(also a symbol or string).
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
It's also possible to delegate a method to the class by using
:class:
class Foo
def self.hello
"world"
end
delegate :hello, to: :class
end
Foo.new.hello # => "world"
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 target is nil and does not respond to the delegated
method a NoMethodError is raised, as with any other value.
Sometimes, however, it makes sense to be robust to that situation and that
is the purpose of the :allow_nil option: If the target is not
nil, or it is and responds to the method, everything works as
usual. But if it is nil and does not respond to the delegated
method, nil is returned.
class User < ActiveRecord::Base
has_one :profile
delegate :age, to: :profile
end
User.new.age # raises NoMethodError: undefined method `age'
But if not having a profile yet is fine and should not be an error condition:
class User < ActiveRecord::Base
has_one :profile
delegate :age, to: :profile, allow_nil: true
end
User.new.age # nil
Note that if the target is not nil then the call is attempted
regardless of the :allow_nil option, and thus an exception is
still raised if said object does not respond to the method:
class Foo
def initialize(bar)
@bar = bar
end
delegate :name, to: :@bar, allow_nil: true
end
Foo.new("Bar").name # raises NoMethodError: undefined method `name'
# File activesupport/lib/active_support/core_ext/module/delegation.rb, line 132 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 prefix, allow_nil = options.values_at(:prefix, :allow_nil) if prefix == true && to =~ /^[^a-z_]/ raise ArgumentError, 'Can only automatically set the delegation prefix when delegating to a method.' end method_prefix = if prefix "#{prefix == true ? to : prefix}_" else '' end file, line = caller.first.split(':', 2) line = line.to_i to = to.to_s to = 'self.class' if to == 'class' methods.each do |method| # Attribute writer methods only accept one argument. Makes sure []= # methods still accept two arguments. definition = (method =~ /[^\]]=$/) ? 'arg' : '*args, &block' # The following generated methods call the target exactly once, storing # the returned value in a dummy variable. # # Reason is twofold: On one hand doing less calls is in general better. # On the other hand it could be that the target has side-effects, # whereas conceptualy, from the user point of view, the delegator should # be doing one call. if allow_nil module_eval(" def #{method_prefix}#{method}(#{definition}) # def customer_name(*args, &block) _ = #{to} # _ = client if !_.nil? || nil.respond_to?(:#{method}) # if !_.nil? || nil.respond_to?(:name) _.#{method}(#{definition}) # _.name(*args, &block) end # end end # end ", file, line - 3) else exception = %Q(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}") module_eval(" def #{method_prefix}#{method}(#{definition}) # def customer_name(*args, &block) _ = #{to} # _ = client _.#{method}(#{definition}) # _.name(*args, &block) rescue NoMethodError => e # rescue NoMethodError => e location = "%s:%d:in `%s'" % [__FILE__, __LINE__ - 2, '#{method_prefix}#{method}'] # location = "%s:%d:in `%s'" % [__FILE__, __LINE__ - 2, 'customer_name'] if _.nil? && e.backtrace.first == location # if _.nil? && e.backtrace.first == location #{exception} # # add helpful message to the exception else # else raise # raise end # end end # end ", file, line - 2) end end end
deprecate :foo
deprecate bar: 'message'
deprecate :foo, :bar, baz: 'warning!', qux: 'gone!'
You can also use custom deprecator instance:
deprecate :foo, deprecator: MyLib::Deprecator.new
deprecate :foo, bar: "warning!", deprecator: MyLib::Deprecator.new
Custom deprecators must respond to
deprecation_warning(deprecated_method_name, message,
caller_backtrace) method where you can implement your custom warning
behavior.
class MyLib::Deprecator
def deprecation_warning(deprecated_method_name, message, caller_backtrace = nil)
message = "#{deprecated_method_name} is deprecated and will be removed from MyLibrary | #{message}"
Kernel.warn message
end
end
DEPRECATED: Use local_constants instead.
Returns the names of the constants defined locally as strings.
module M
X = 1
end
M.local_constant_names # => ["X"]
This method is useful for forward compatibility, since Ruby 1.8 returns constant names as strings, whereas 1.9 returns them as symbols.
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"
end
AppConfiguration.google_api_key # => "123456789"
AppConfiguration.google_api_key = "overriding the api key!"
AppConfiguration.google_api_key # => "overriding the api key!"
To opt out of the instance writer method, pass instance_writer:
false. To opt out of the instance reader method, pass
instance_reader: false. To opt out of both instance methods,
pass instance_accessor: false.
# 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| raise NameError.new('invalid attribute name') unless sym =~ /^[_A-Za-z]\w*$/ class_eval(" @@#{sym} = nil unless defined? @@#{sym} def self.#{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) unless options[:instance_reader] == false || options[:instance_accessor] == false class_eval(" def #{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) end end end
# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 26 def mattr_writer(*syms) options = syms.extract_options! syms.each do |sym| raise NameError.new('invalid attribute name') unless sym =~ /^[_A-Za-z]\w*$/ class_eval(" def self.#{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) unless options[:instance_writer] == false || options[:instance_accessor] == false class_eval(" def #{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) end end 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
Returns the name of the module containing this one.
M::N.parent_name # => "M"
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]
# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 46 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
# File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 26 def qualified_const_defined?(path, search_parents=true) QualifiedConstUtils.raise_if_absolute(path) QualifiedConstUtils.names(path).inject(self) do |mod, name| return unless mod.const_defined?(name, search_parents) mod.const_get(name) end return true end
# File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 44 def qualified_const_set(path, value) QualifiedConstUtils.raise_if_absolute(path) const_name = path.demodulize mod_name = path.deconstantize mod = mod_name.empty? ? self : qualified_const_get(mod_name) mod.const_set(const_name, value) end