How can I access the current __FILE__ in a subclass from a method in the superclass in ruby

Question

I'm hoping to set up a default path for logging, relative to the path of the file using the log, something like this:

# /path/to/lib/bar.rb
class Bar
  def settings_file_path
    File.dirname(File.expand_path(__FILE__))
  end
end

# /path/to/app/models/foo.rb
class Foo < Bar
end

Foo.new.settings_file_path

Ideal output:

# => /path/to/app/models

Actual output:

# => /path/to/lib

Because FILE references the file where it's written, not where it's being called from, it's returning the bar.rb file, but I want something like this to return the path of the foo.rb file, even though the method is defined in Bar.

Anybody have any suggestions?

Answer 1

caller.first[/^[^:]+/] will not work on Windows because absolute path there looks like $DRIVE:$PATH (example C:/Windows/system32)

Instead caller.first[/^[^:]+/] use caller_locations.first.absolute_path

Answer 2

The simplest would be something like this:

# foo.rb
class Foo
  def self.my_file
    @my_file
  end
end

# bar.rb
class Bar < Foo
  @my_file = __FILE__
end

# main.rb
require_relative 'foo'
require_relative 'bar'
p Bar.my_file
#=> "/Users/phrogz/Desktop/bar.rb"

However, you could parse the caller in a self.inherited hook like so:

# foo.rb
class Foo
  class << self
    attr_accessor :_file
  end
  def self.inherited( k )
    k._file = caller.first[/^[^:]+/]
  end
end

# bar.rb
class Bar < Foo
end

# main.rb
require_relative 'foo'
require_relative 'bar'

p Bar._file
#=> "/Users/phrogz/Desktop/bar.rb"

I'm not certain how robust or portable that parsing is; I suggest you test it.

N.B. My Bar inherits from Foo, the reverse of your question. Be not confused by the differences in our setups.