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
Copyright (c) 2014 Rubyworks (BSD-2 License)
See LICENSE.txt for details.