Question

I have an existing class with many instance methods. I’d like to encapsulate (or subclass) that class, such that the new class can have all those original instance methods called on it, and simply delegate to the inner (or parent) class, but also call its own code before and after the delegation.

For example, here is some pseudocode I’d be looking for:

class Wrapper
  def initialize(inner)
    @inner = inner
  end

  def __getattr__(method_name, *method_args) # <-- made up syntax
    # do something before
    ret = @inner.method_name(*method_args) # <-- made up syntax, call method on inner
    # do something after
    ret
  end

What is the best way to implement this in ruby? Thanks

Answer 1

Something like:

def method_missing(method_name, *method_args, &block) # <-- made up syntax
  if @inner.respond_to? method_name
    # do something before
    ret = @inner.send(method_name, *method_args, &block) # <-- made up syntax, call method on inner
    # do something after
    ret
  else
    super(method_name, *method_args, &block)
  end
end

Should do the trick.