I was trying to add a method to the String class. This method should mutate the current string (of course it would be possible to write a not mutating version but I'd prefer the mutating one). I had no idea how to do this and after some googling I found the method rb_str_modify which makes a given string mutable. That's exactly what I need but I couldn't find an equivalent in the Ruby language. Did I miss something or is there really no possibility in the language itself?
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1 Answer
Reopening Classes
All classes in Ruby are open for extension so you can simply do this ...
Class String
def my_new_method(args)
# Some sort of modification to self
self.replace "SOME CALCULATED VALUE"
end
end
... somewhere in your code. I've modified string a few times in different applications - usually I just put the modifications into one particular module, making it easy to reuse them or remove them as required.
Modifying individual objects
Modifying a class in its entirety is dangerous as it's very difficult to identify all of the consequences - I once broke Merb by modifying a method in the String class. It's much safer to modify particular objects. This is easy in Ruby - you use the extend keyword. You define a module, add your function and then modify the target object. This example ...
module Humor
def tickle
"hee, hee!"
end
end
a = "Grouchy"
a.extend Humor
a.tickle » "hee, hee!"
is taken from the Pickaxe book
Chris
1 Comment
Hagbard
Thank you very much. #replace is a great idea. It works pretty well for my case. I expect no bad consequences. It's just a little method which is really helpful in general.