asemanfar - a blog about programming

Monkey Patching Galore

March 03, 2008

Here is some code I just threw together for fun, I don't actually use it. Some would call this monkey patching.

   1  class Symbol
   2    def to_proc
   3      Proc.new { |*args| args.shift.__send__(self, *args) } 
   4    end
   5  end
   6  
   7  class Array
   8    def all?(*args, &block)
   9      !!self.each { |e| return false unless block.call(e, *args) } 
  10    end
  11    
  12    def array_of?(klass)
  13      self.all?(klass, &:is_a?)
  14    end
  15  end
  16  
  17  
  18  puts ["Will", "this", "work?"].array_of?(String) # => true
  19  
  20  puts ["But", "this", 1, "will", "be false"].array_of?(String) # => false
  21  
  22  puts ["But", "wait", "this still works"].all?(&:to_s) # => true

Alright, so I used the well-known Symbol#to_proc, redefined Array#all? and added a method Array#array_of?. But look, Array#all? still works when you try to use it the original way. If you don't like my code, don't use it. I wouldn't.

What would have been a non-monkey patch way of doing this?

   1  class SingleTypedArray < Array
   2    def array_of?(klass)
   3      !!self.each { |e| return false unless e.is_a?(klass) }
   4    end
   5  end

But hey, that's gross. I lose my ability to do [elem1, elem2], I have to do SingleTypedArray.new(elem1, elem2, ...).

I've run into a lot of Rails plugins that add functionality to existing classes, such as ActiveRecord and some of them do it in an obtrusive way, so I simply choose not to use that plugin. You are not required to use a plugin, library, or gem that does something you want if it does it grossly. There are a lot of plugins and gems out there, but a lot of them suck and are poorly designed. Pick and choose the ones that do it right.

Basically: it's not Ruby, it's some programmers.

"Guns don't kill people. People kill people."