Ruby script execution within a module

Question

Why is is that the following fails?

module Test
    def test
        puts "test"
    end

    puts "testing"
    test
end

I get this output:

testing
test.rb:6:in `test': wrong number of arguments (ArgumentError)
    from test.rb:6:in `<module:Test>'
    from test.rb:1:in `<main>'

Is it because the module hasn't been "compiled" yet, since the end keyword hasn't been reached?

Answer 1

I think the definition needs to be:

def Test.test
    puts "test"
end

Answer 2

test is not calling the method you defined: it is invoking Kernel.test, which expects 2 arguments -- thus the ArgumentError exception.

Answer 3

Using a previously unused name might clear up your confusion:

module Test
  def my_test
    puts "my_test"
  end
  puts "testing"
  my_test
end

results in

testing
NameError: undefined local variable or method `my_test' for Test:Module

Inside the module...end block, when you invoke my_test, what is self (the implicit receiver)? It is the module Test. And there is no my_test "module method". The my_test method defined above is like an instance method, to be sent to some object that includes this module.

You need to define my_test as a "module method":

module Test
  def self.my_test
    puts "my_test"
  end
  puts "testing"
  my_test
end

results in

testing
my_test

If you want my_test as an instance method and you want to invoke it inside your module definition:

method Test
  puts "testing"
  Object.new.extend(self).my_test
end

gives

testing
my_test

Answer 4

module Test
  def test # This is an instance method
    puts "test"
  end

  puts "testing"
  test     # This is a call to a module method
end

The two are completely unrelated. Somewhere higher up in your inheritance chain, you have a module method named test which takes at least one argument. (I'm guessing it is the Kernel#test method, which takes two arguments.) Since you call it without an argument, you get an ArgumentError exception.

If you were to provide a little more detail about what the actual problem is, that you are trying to solve, it would be possible to give a better answer. Until then, here's a couple of ideas:

Make the method a module method:

module Test
  def self.test; puts "test" end

  puts "testing"
  test
end

Extend the module with itself:

module Test
  def test; puts "test" end

  extend self

  puts "testing"
  test
end

Create an instance of the module:

module Test
  def test; puts "test" end
end

puts "testing"
Object.new.extend(Test).test

Mix the module into a class, and create an instance of that:

module Test
  def test; puts "test" end
end

class Foo; include Test end

puts "testing"
Foo.new.test

Mix the module into Module:

module Test
  def test; puts "test" end
end

class Module; include Test end

module Test
  puts "testing"
  test
end

Mix the module into Object:

module Test
  def test; puts "test" end
end

class Object; include Test end

puts "testing"
test

Mix the module into the main object:

module Test
  def test; puts "test" end
end

include Test

puts "testing"
test