Andrew Fecheyr

Method Introspection in Ruby

July 15, 2011
If, at runtime, you want to find out what the argument names of a Ruby method are, you can use method introspection:

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include Test::Unit::Assertions 
  #=> Object
m = method(:assert_in_delta)
  #=> #<Method: Object(MiniTest::Assertions)#assert_in_delta>
m.methods - Object.methods
  #=> [:call, :[], :arity, :to_proc, :receiver, :owner, :unbind, :source_location, :parameters]
m.parameters
  #=> [[:req, :exp], [:req, :act], [:opt, :delta], [:opt, :msg]]
m.arity
  #=> -3
m.source_location
  #=> ["/Users/andrew/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/minitest/unit.rb", 122]

Yay for meta programming! And possibly useful for building a dynamic interfaces.

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