Ruby Language method_missing
Parameters
| Parameter | Details |
|---|---|
| method | The name of the method that has been called (in the above example this is :say_moo, note that this is a symbol. |
| *args | The arguments passed in to this method. Can be any number, or none |
| &block | The block of the method called, this can either be a do block, or a { } enclosed block |
Remarks
Always call super, at the bottom of this function. This saves silent failure when something is called and you don't get an error.
For example, this method_missing is going to cause problems:
class Animal
def method_missing(method, *args, &block)
say, speak = method.to_s.split("_")
if say == "say"
speak
end
end
end
=> Animal.new.foobar
=> nil # This should really be raising an error
method_missing is a good tool to use when appropriate, but has two costs you should consider. First, method_missing is less efficient -- ruby must search the class and all of its ancestors before it can fall back on this approach; this performance penalty may be trivial in a simple case, but can add up. Second and more broadly, this is a form of meta-programming that has great power that comes with responsibility to ensure that the implementation is secure, properly handles malicious inputs, unexpected inputs, and so on.
You should also override respond_to_missing? like so:
class Animal
def respond_to_missing?(method, include_private = false)
method.to_s.start_with?("say_") || super
end
end
=> Animal.new.respond_to?(:say_moo) # => true
