Maintenance of Ruby 2.0.0 ended on February 24, 2016. Read more
BasicObject
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 if the use of Delegator:
class SimpleDelegator < Delegator def initialize(obj) super # pass obj to Delegator constructor, required @delegate_sd_obj = obj # store obj for future use end 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
Be advised, RDoc will not detect delegated methods.
Delegates ! to the _getobj_
# File delegate.rb, line 136 def ! !__getobj__ end
Returns true if two objects are not considered of equal value.
# File delegate.rb, line 128 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 120 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 144 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 152 def __setobj__(obj) raise NotImplementedError, "need to define `__setobj__'" end
Freeze both the object returned by _getobj_ and self.
# File delegate.rb, line 214
Serialization support for the object returned by _getobj_.
# File delegate.rb, line 159 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 171 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
Handles the magic of delegation through _getobj_.
# File delegate.rb, line 69 def method_missing(m, *args, &block) target = self.__getobj__ begin target.respond_to?(m) ? target.__send__(m, *args, &block) : super(m, *args, &block) ensure $@.delete_if {|t| %r"\A#{Regexp.quote(__FILE__)}:#{__LINE__-2}:"o =~ t} if $@ end end
Returns the methods available to this delegate object as the union of this object's and _getobj_ methods.
# File delegate.rb, line 95 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 111 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 103 def public_methods(all=true) __getobj__.public_methods(all) | super end
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
# File delegate.rb, line 82 def respond_to_missing?(m, include_private) r = self.__getobj__.respond_to?(m, include_private) if r && include_private && !self.__getobj__.respond_to?(m, false) warn "#{caller(3)[0]}: delegator does not forward private method \##{m}" return false end r end
Taint both the object returned by _getobj_ and self.
# File delegate.rb, line 204
Trust both the object returned by _getobj_ and self.
# File delegate.rb, line 194