From: Rob Marshall <lists@...>
Date: 2013-02-06T05:15:30+09:00
Subject: Implementing DRY with a function call

Hi,

I'm working on my first Ruby project...and I'm trying to adhere to the
DRY principle. What I have is a lot, and I mean a LOT, of repetition.
The calls all look similar to this (by the way I'm writing an interface
to a library with FFI):

module MyLibrary
  extend FFI::Library
  ffi_lib [MyLibrary]

  attach_function :LibFunc, [ :string, :pointer ], :void
  attach_function :CheckError, [], :int

  class SubClass
     def lib_func(name)
        ret = FFI::MemoryPointer.new(:char,256)
        MyLibrary.LibFunc(name,ret)
        if MyLibrary.CheckError != 0
          raise "You got an error"
        end
     end
  end
end

That's the basic idea, but I have several classes within the module,
each with a dozen, or more, functions. What I am doing now is, within
the module:

  def call_check_error(function)
    ret = lambda {function}.call
    if MyLibrary.CheckError != 0
      raise "You got an error"
    end
    return ret
  end

For functions that don't actually return a value, ret is nil, so I can
just ignore it when I don't need it, and that way I avoid having to have
two methods, one with, and one without, a return. So that in lib_func I
do:

    def lib_func(name)
      ret = FFI::MemoryPointer.new(:char, 256)
      MyLibrary.call_check_error(MyLibrary.LibFunc(name,ret))
    end

This seems to be working fine, although I've just started doing it this
way.

So my question is: Is that a good way to implement this? I'm assuming
it's probably not the best way, and I would hope someone with more
experience with Ruby might have a suggestion. It kind of feels like:

lambda {function}.call

is a bit hokey, but I wasn't sure how else to do it.

Thanks,

Rob

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