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Feature #19521

Updated by ioquatix (Samuel Williams) over 1 year ago

See https://bugs.ruby-lang.org/issues/19450 for previous discussion and motivation. 

 This proposal introduces `Module#name=` (and thus also `Class#name`) `Class#name=` to set the temporary class name. The name assignment has no effect if the module/class already has a permanent name. This is an alternative or addition to <https://bugs.ruby-lang.org/issues/19520>. 

 ```ruby 
 c = Class.new do 
   self.name = "fake name" 
 end 

 c = Class.new 
 c.name = "fake name" 
 ``` 

 Alternatively, we could use `set_name`: 

 ```ruby 
 Class.new do 
   set_name "fake_name" 
 end 
 ``` 

 ## Example usage 

 The current Ruby test suite has code which shows the usefulness of this new method: 

 ```ruby 
   def labeled_module(name, &block) 
     Module.new do 
       singleton_class.class_eval { 
         define_method(:to_s) {name} 
         alias inspect to_s 
         alias name to_s 
       } 
       class_eval(&block) if block 
     end 
   end 
   module_function :labeled_module 

   def labeled_class(name, superclass = Object, &block) 
     Class.new(superclass) do 
       singleton_class.class_eval { 
         define_method(:to_s) {name} 
         alias inspect to_s 
         alias name to_s 
       } 
       class_eval(&block) if block 
     end 
   end 
   module_function :labeled_class 
 ``` 

 The updated code would look like this: 

 ```ruby 
   def labeled_module(name, &block) 
     Module.new do 
       self.name = name 
       class_eval(&block) if block 
     end 
   end 

   def labeled_class(name, superclass = Object, &block) 
     Class.new(superclass) do 
       self.name = name 
       class_eval(&block) if block 
     end 
   end 
   module_function :labeled_class 
 ``` 

 Because the name cannot be set as part of `.new`, we have to have a separate block to set the name, before calling `class_eval`. I think the ergonomics and performance of this are slightly worse than the [counter proposal](https://bugs.ruby-lang.org/issues/19520).

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