Class: Delegator
- Inherits:
- BasicObject
- Defined in:
- lib/delegate.rb
Overview
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
Notes
Be advised, RDoc will not detect delegated methods.
Direct Known Subclasses
Class Method Summary collapse
-
.const_missing(n) ⇒ Object
:stopdoc:.
-
.delegating_block(mid) ⇒ Object
:nodoc:.
-
.public_api ⇒ Object
:nodoc:.
Instance Method Summary collapse
-
#! ⇒ Object
Delegates ! to the _getobj_.
-
#!=(obj) ⇒ Object
Returns true if two objects are not considered of equal value.
-
#==(obj) ⇒ Object
Returns true if two objects are considered of equal value.
-
#__getobj__ ⇒ Object
This method must be overridden by subclasses and should return the object method calls are being delegated to.
-
#__setobj__(obj) ⇒ Object
This method must be overridden by subclasses and change the object delegate to obj.
-
#initialize(obj) ⇒ Delegator
constructor
Pass in the obj to delegate method calls to.
-
#marshal_dump ⇒ Object
Serialization support for the object returned by _getobj_.
-
#marshal_load(data) ⇒ Object
Reinitializes delegation from a serialized object.
-
#method ⇒ Object
:method: freeze Freeze both the object returned by _getobj_ and self.
-
#method_missing(m, *args, &block) ⇒ Object
Handles the magic of delegation through _getobj_.
-
#methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ methods.
-
#protected_methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ protected methods.
-
#public_methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ public methods.
-
#respond_to_missing?(m, include_private) ⇒ Boolean
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
Constructor Details
#initialize(obj) ⇒ Delegator
Pass in the obj to delegate method calls to. All methods supported by obj will be delegated to.
75 76 77 |
# File 'lib/delegate.rb', line 75 def initialize(obj) __setobj__(obj) end |
Dynamic Method Handling
This class handles dynamic methods through the method_missing method
#method_missing(m, *args, &block) ⇒ Object
Handles the magic of delegation through _getobj_.
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 |
# File 'lib/delegate.rb', line 82 def method_missing(m, *args, &block) r = true target = self.__getobj__ {r = false} begin if r && target.respond_to?(m) target.__send__(m, *args, &block) elsif ::Kernel.respond_to?(m, true) ::Kernel.instance_method(m).bind(self).(*args, &block) else super(m, *args, &block) end ensure $@.delete_if {|t| %r"\A#{Regexp.quote(__FILE__)}:(?:#{[__LINE__-7, __LINE__-5, __LINE__-3].join('|')}):"o =~ t} if $@ end end |
Class Method Details
.const_missing(n) ⇒ Object
:stopdoc:
60 61 62 |
# File 'lib/delegate.rb', line 60 def self.const_missing(n) ::Object.const_get(n) end |
.delegating_block(mid) ⇒ Object
:nodoc:
345 346 347 348 349 350 351 352 353 354 |
# File 'lib/delegate.rb', line 345 def Delegator.delegating_block(mid) # :nodoc: lambda do |*args, &block| target = self.__getobj__ begin target.__send__(mid, *args, &block) ensure $@.delete_if {|t| /\A#{Regexp.quote(__FILE__)}:#{__LINE__-2}:/o =~ t} if $@ end end end |
.public_api ⇒ Object
:nodoc:
244 245 246 |
# File 'lib/delegate.rb', line 244 def self.public_api # :nodoc: @delegator_api end |
Instance Method Details
#! ⇒ Object
Delegates ! to the _getobj_
158 159 160 |
# File 'lib/delegate.rb', line 158 def ! !__getobj__ end |
#!=(obj) ⇒ Object
Returns true if two objects are not considered of equal value.
150 151 152 153 |
# File 'lib/delegate.rb', line 150 def !=(obj) return false if obj.equal?(self) __getobj__ != obj end |
#==(obj) ⇒ Object
Returns true if two objects are considered of equal value.
142 143 144 145 |
# File 'lib/delegate.rb', line 142 def ==(obj) return true if obj.equal?(self) self.__getobj__ == obj end |
#__getobj__ ⇒ Object
This method must be overridden by subclasses and should return the object method calls are being delegated to.
166 167 168 |
# File 'lib/delegate.rb', line 166 def __getobj__ __raise__ ::NotImplementedError, "need to define `__getobj__'" end |
#__setobj__(obj) ⇒ Object
This method must be overridden by subclasses and change the object delegate to obj.
174 175 176 |
# File 'lib/delegate.rb', line 174 def __setobj__(obj) __raise__ ::NotImplementedError, "need to define `__setobj__'" end |
#marshal_dump ⇒ Object
Serialization support for the object returned by _getobj_.
181 182 183 184 185 186 187 188 |
# File 'lib/delegate.rb', line 181 def marshal_dump ivars = instance_variables.reject {|var| /\A@delegate_/ =~ var} [ :__v2__, ivars, ivars.map{|var| instance_variable_get(var)}, __getobj__ ] end |
#marshal_load(data) ⇒ Object
Reinitializes delegation from a serialized object.
193 194 195 196 197 198 199 200 201 |
# File 'lib/delegate.rb', line 193 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 |
#method ⇒ Object
:method: freeze Freeze both the object returned by _getobj_ and self.
236 237 238 239 240 241 |
# File 'lib/delegate.rb', line 236 [:trust, :untrust, :taint, :untaint, :freeze].each do |method| define_method method do __getobj__.send(method) super() end end |
#methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ methods.
117 118 119 |
# File 'lib/delegate.rb', line 117 def methods(all=true) __getobj__.methods(all) | super end |
#protected_methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ protected methods.
133 134 135 |
# File 'lib/delegate.rb', line 133 def protected_methods(all=true) __getobj__.protected_methods(all) | super end |
#public_methods(all = true) ⇒ Object
Returns the methods available to this delegate object as the union of this object’s and _getobj_ public methods.
125 126 127 |
# File 'lib/delegate.rb', line 125 def public_methods(all=true) __getobj__.public_methods(all) | super end |
#respond_to_missing?(m, include_private) ⇒ Boolean
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
102 103 104 105 106 107 108 109 110 111 |
# File 'lib/delegate.rb', line 102 def respond_to_missing?(m, include_private) r = true target = self.__getobj__ {r = false} r &&= target.respond_to?(m, include_private) if r && include_private && !target.respond_to?(m, false) warn "#{caller(3)[0]}: delegator does not forward private method \##{m}" return false end r end |