class Delegator
This library provides three different ways to delegate method calls to an object. The easiest to use is SimpleDelegator
. Pass an object to the constructor and all methods supported by the object will be delegated. This object can be changed later.
Going a step further, the top level DelegateClass method allows you to easily setup delegation through class inheritance. This is considerably more flexible and thus probably the most common use for this library.
Finally, if you need full control over the delegation scheme, you can inherit from the abstract class Delegator
and customize as needed. (If you find yourself needing this control, have a look at Forwardable which is also in the standard library. It may suit your needs better.)
SimpleDelegator’s implementation serves as a nice example of the use of Delegator:
require 'delegate' class SimpleDelegator < Delegator def __getobj__ @delegate_sd_obj # return object we are delegating to, required end def __setobj__(obj) @delegate_sd_obj = obj # change delegation object, # a feature we're providing end end
Notes¶ ↑
Be advised, RDoc will not detect delegated methods.
Constants
- KERNEL_RESPOND_TO
- VERSION
Public Class Methods
Pass in the obj to delegate method calls to. All methods supported by obj will be delegated to.
# File delegate.rb, line 75 def initialize(obj) __setobj__(obj) end
Public Instance Methods
Delegates ! to the _getobj_
# File delegate.rb, line 180 def ! !__getobj__ end
Returns true if two objects are not considered of equal value.
# File delegate.rb, line 164 def !=(obj) return false if obj.equal?(self) __getobj__ != obj end
Returns true if two objects are considered of equal value.
# File delegate.rb, line 156 def ==(obj) return true if obj.equal?(self) self.__getobj__ == obj end
This method must be overridden by subclasses and should return the object method calls are being delegated to.
# File delegate.rb, line 188 def __getobj__ __raise__ ::NotImplementedError, "need to define `__getobj__'" end
This method must be overridden by subclasses and change the object delegate to obj.
# File delegate.rb, line 196 def __setobj__(obj) __raise__ ::NotImplementedError, "need to define `__setobj__'" end
Returns true if two objects are considered of equal value.
# File delegate.rb, line 172 def eql?(obj) return true if obj.equal?(self) obj.eql?(__getobj__) end
:method: freeze Freeze both the object returned by _getobj_ and self.
# File delegate.rb, line 237 def freeze __getobj__.freeze super() end
Serialization support for the object returned by _getobj_.
# File delegate.rb, line 203 def marshal_dump ivars = instance_variables.reject {|var| /\A@delegate_/ =~ var} [ :__v2__, ivars, ivars.map {|var| instance_variable_get(var)}, __getobj__ ] end
Reinitializes delegation from a serialized object.
# File delegate.rb, line 215 def marshal_load(data) version, vars, values, obj = data if version == :__v2__ vars.each_with_index {|var, i| instance_variable_set(var, values[i])} __setobj__(obj) else __setobj__(data) end end
# File delegate.rb, line 82 def method_missing(m, *args, &block) r = true target = self.__getobj__ {r = false} if r && target_respond_to?(target, m, false) target.__send__(m, *args, &block) elsif ::Kernel.method_defined?(m) || ::Kernel.private_method_defined?(m) ::Kernel.instance_method(m).bind_call(self, *args, &block) else super(m, *args, &block) end end
Returns the methods available to this delegate object as the union of this object’s and _getobj_ methods.
# File delegate.rb, line 131 def methods(all=true) __getobj__.methods(all) | super end
Returns the methods available to this delegate object as the union of this object’s and _getobj_ protected methods.
# File delegate.rb, line 147 def protected_methods(all=true) __getobj__.protected_methods(all) | super end
Returns the methods available to this delegate object as the union of this object’s and _getobj_ public methods.
# File delegate.rb, line 139 def public_methods(all=true) __getobj__.public_methods(all) | super end
Use #__raise__ if your Delegator
does not have a object to delegate the raise
method call.
# File delegate.rb, line 66
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
# File delegate.rb, line 99 def respond_to_missing?(m, include_private) r = true target = self.__getobj__ {r = false} r &&= target_respond_to?(target, m, include_private) if r && include_private && !target_respond_to?(target, m, false) warn "delegator does not forward private method \##{m}", uplevel: 3 return false end r end
Private Instance Methods
Handle BasicObject instances
# File delegate.rb, line 114 def target_respond_to?(target, m, include_private) case target when Object target.respond_to?(m, include_private) else if KERNEL_RESPOND_TO.bind_call(target, :respond_to?) target.respond_to?(m, include_private) else KERNEL_RESPOND_TO.bind_call(target, m, include_private) end end end