Reusing

Short Story

Reusing allows one to use refinements directly from an extension file.

require 'reusing'

using 'some_extension_script'

Long Story

Ruby introduced refinements in version 2.0. Refinements are essentially a safe alternative to monkey-patching. Unfortunately, a serious problem with the syntax of refinements is the degree to which they differ from writing tradition class extensions. Traditionally, if you want to add a method to the String class, for instance, you simply open the class and define them method.

class String
  def some_method
    ...
  end
end

And that's it. You could put that code in a file and require as needed. Refinements, on the other hand, hand much more boiler-plate. The above would have to be written:

module SomeModule
  refine String do
    def some_method
      ...
    end
  end
end

using SomeModule

This can be put in a file too, but the using SomeModule will have to be reissued in every file the refinement is needed.

For a one off use, this isn't a big deal. But for a method library such as Ruby Facets, this has huge implications. In fact, Facets does not yet support refinements precisely b/c of this issue. To do so would require maintaining a second copy of every method in refinement format. While doable, it is obviously not DRY, and quite simply a pain in the ass.

So the idea of overriding the using method to accept a library file name was hatched. With it, most extension scripts can be readily used as-is, without all the boiler-plate. Usage is pretty simple. Let's say the example given above is in a library file called some_method.rb, then we can do:

require 'reusing'

using 'some_method'

The refinement method will find the file, read it in, perform a transformation converting class String into refine String do and wrap it all in a module which it then passes to the original using method, which has been aliased, btw, as reusing (hence the name of this library).

Caveats

Unfortunately the implementation of Reusing is necessarily a bit hackish. Although it works fine for basic extensions scripts there are complications if, for instance, the script requires another extension script. While the scripts extensions will become refinements, the further requirements will not.

Thoughts

Probably the ideal solution would be if refinement syntax could use normal class and module keywords, instead of the special refine clause.

module M
  class String
    def important!
      self + "!"
    end
  end
end

# refinement
using M::*

In conjunction with this is should be possible to monkey patch with the same code as well.

# core extension
patch M::*

In this way the both techniques could be used via the same code, while still being modular.

Copyrights

See LICENSE.txt for details.