RCR 309: __DIR__

Hi --

You could define it as a method:

  module Kernel
    def __DIR__
      File.dirname(__FILE__)
    end
  end 

David Black

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Ah, Kernel method. Of course. Thanks. Had constant stuck in my mind for some reason.

T.

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I should point out for those who don;t see it right off, that this is still a viable addition despite it being definable as a kernel method. Notice that the kernel method will always return the directory location of the file it is defined in, not the one you call it from. So it doesn't really work.

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module Kernel

  def __DIR__
    (/^(.+)?:\d+/ =~ caller[0]) ? File.dirname($1) : nil
  end

end

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Hey, thanks! That went right into Facets. If you would like I can credit you in the source code, whomever you are?

T. (Trans)

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IMO this method should continue to work even if the user changes the current directory; I don't believe the above implementations do. You can use File.expand_path to expand the path relative to a given directory, namely the current working directory at the time the file was loaded. I haven't tried it, but my first pass would be to modify the above code to:

  module Kernel
    BASE_DIR = Dir.getwd
    def __DIR__
      (/^(.+)?:\d+/ =~ caller[0]) ? File.expand_path(File.dirname($1), BASE_DIR) : nil
    end
  end

though this is still not perfect if a library changes the current working directory when it is required (which is a bad thing to do IMO, but nevertheless possible).

I believe that a perfect solution in pure ruby would be too complex to be worthwhile. I would rather see this implemented in C.

-- Paul Brannan

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