From: LAMBEAU Bernard <blambeau@...>
Date: 2009-04-08T23:40:43+09:00
Subject: Re: performing an action only the first time a function called

One way to do it, which requires a good understanding of
metaprogramming, could be as follows:

class Class

  # Replaces the method whose name is provided by a
  # method that calls the original one the first time it is called
  # and by a noop method for subsequent calls.
  def one_call_only(method_name)
    # implement me
  end

end

class MyClass
  def bootstrapDirectXSDK
    bootstrapBuildToolsDirectory("DirectX/#{DIRECTX_VERSION}")
  end
  one_call_only :bootstrapDirectXSDK
end

I'm not sure it's the simplest way to do it. I can sketch the actual
code of one_call_only if it helps.

blambeau

On Wed, Apr 8, 2009 at 4:29 PM, James French
<James.French@naturalmotion.com> wrote:
> Hi,
>
> Could anyone suggest an elegant way of doing something like:
>
> $directXSDKBootstrapped = false
>
> def bootstrapDirectXSDK
>  if !$directXSDKBootstrapped
>    bootstrapBuildToolsDirectory("DirectX/#{DIRECTX_VERSION}")
>    $directXSDKBootstrapped = true
>    $directXSDKBootstrapped.freeze
>  end
> end
>
> Obviously the intention is to only do something the first time it is called. Maybe some little reusable util? I have a number of different bootstrap functions I want to apply this to.
>
> Cheers,
> James
>
>