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
Source
# File lib/delegate.rb, line 75 def initialize(obj) __setobj__(obj) end
Pass in the obj to delegate method calls to. All methods supported by obj will be delegated to.
Public Instance Methods
Source
# File lib/delegate.rb, line 164 def !=(obj) return false if obj.equal?(self) __getobj__ != obj end
Returns true if two objects are not considered of equal value.
Source
# File lib/delegate.rb, line 156 def ==(obj) return true if obj.equal?(self) self.__getobj__ == obj end
Returns true if two objects are considered of equal value.
Source
# File lib/delegate.rb, line 188 def __getobj__ __raise__ ::NotImplementedError, "need to define '__getobj__'" end
This method must be overridden by subclasses and should return the object method calls are being delegated to.
Source
# File lib/delegate.rb, line 196 def __setobj__(obj) __raise__ ::NotImplementedError, "need to define '__setobj__'" end
This method must be overridden by subclasses and change the object delegate to obj.
Source
# File lib/delegate.rb, line 172 def eql?(obj) return true if obj.equal?(self) obj.eql?(__getobj__) end
Returns true if two objects are considered of equal value.
Source
# File lib/delegate.rb, line 237 def freeze __getobj__.freeze super() end
:method: freeze Freeze both the object returned by _getobj_ and self.
Source
# File lib/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
Serialization support for the object returned by _getobj_.
Source
# File lib/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
Reinitializes delegation from a serialized object.
Source
# File lib/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
BasicObject#method_missing
Source
# File lib/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_ methods.
Source
# File lib/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_ protected methods.
Source
# File lib/delegate.rb, line 139 def public_methods(all=true) __getobj__.public_methods(all) | super end
Returns the methods available to this delegate object as the union of this object’s and _getobj_ public methods.
Source
# File lib/delegate.rb, line 66
Use __raise__
if your Delegator
does not have a object to delegate the raise
method call.
Source
# File lib/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
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
Private Instance Methods
Source
# File lib/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
Handle BasicObject
instances