Metaprogramming. What a lovely buzz word. I guess I’ve heard it enough and knew what the short definition is. Metaprogramming is code that writes code. I think it is one of those things I just never thought about, even though I had used concepts and even written some before without realizing it until recently.
Here is a short and simple example.
class Something
@my_hash = {"foo" => "1234", "bar" => "5678"}
def initialize
@my_hash.each do |a, b|
self.instance_eval do
define_method(a.to_s) {b.to_s}
end
end
end
end
And now we can play with it.
a = Something.new a.foo # => 1234 a.bar # => 5678
Now, what happened here is pretty neat in my opinion. We took our hash, my_hash, and in our initialize method, created two instance methods from its values. define_method is what did all the magic. You need to pass it a proc or, like what I did, just give it a simple block (just the string value from my hash).
Pretty neat, eh?