show source files of a class or method

source.rb

find_source = lambda do |clazz, include_super=false| 
  files = clazz.methods(include_super).inject([]) {|c, m| c << clazz.method(m).source_location.first if clazz.method(m) and clazz.method(m).source_location; c }
  files.uniq
end

puts find_source.call(Rails)

puts self.method(:get).source_location