Corrects to_xml in TwiML generation

[philnash]

Twilio::TwiML::TwiML#to_xml was being aliased to to_s before to_s was defined so took on the old definition.

This PR adds tests for using to_xml and fixes the aliasing. It also removes the reference to builder in the README.

[ilanbiala]

If the alias has to go in a specific order to work properly, then I think it makes more sense to just explicitly define to_xml and call to_s within the method to avoid confusion.

Also, does this error not exist for:

lib/twilio-ruby/jwt/client_capability.rb
15:      alias to_s to_jwt

[philnash]

As this is Ruby, it is interpreted and run in order. At the point in the class definition where to_xml is aliased to to_s, to_s had been defined by an ancestor class and to_xml took on that definition. To move it here means that to_xml takes on the correct defintion of to_s.

This didn't cause an issue in client_capability.rb because the ClientCapability class itself doesn't define to_s, it is taken from BaseJWT which was defined before ClientCapability and therefore to_xml takes on the right definition.

There are a couple of articles that describe how alias works, and compare to alias_method:

• http://blog.bigbinary.com/2012/01/08/alias-vs-alias-method.html
• https://ernie.io/2014/10/23/in-defense-of-alias/

They both unintentionally show one thing, when using alias Ruby developers do so straight after defining the method they are aliasing to something else. So this placement of alias to_xml to_s is both correct and more rubyish than before.

One other thing, the existence of alias to_s to_jwt in ClientCapability and def to_s ; to_jwt ; end in AccessToken shows that some more refactoring can be done. PR incoming.

[ilanbiala]

Yeah I figured it was interpreted in order. After reading the articles and thinking a bit, I think it makes more sense to explicitly define the method and just call the true function from within, like:

def to_xml
  to_s
end

because there is some controversy. However, are methods defined in order as well? Meaning, if we put the to_xml definition above to_s, will it use some standard to_s method and not one defined later in the class?

[philnash]

There's no controversy, just the right way to use each of the methods, which is as described. Aliasing to_s to to_xml here is perfectly clear.

I think it would look un-Ruby to just do def to_xml ; to_s ; end. It wouldn't be order defined, to_s would be looked up dynamically at runtime.