Concerning the #to_* convention

ruby-talk
1

Howdy partners! I'm having a bit of fun writing a Ruby XML document object model (yes, I'm aware of the fact that there already exists such models), and I'm using #to_* throughout the code. I'm just wondering if a #to_* method always should return a copy of the receiver, in the format specified by * (e.g. `str', `i'), or if it's okay to just pass a reference to the receiver itself?

Consider this:

   class Namespace
     def to_xml_ns
       self # should this be a copy?
     end
   end

   class Element < Node
     def initialize(opts = {})
       if opts[:namespace]
         # `namespace' quacks like a Namespace object
         if opts[:namespace].respond_to? :to_xml_ns
           # I'd like a Namespace object in @namespace.
           @namespace = opts[:namespace].to_xml_ns
         # `namespace' quakcs like a String object
         elsif opts[:namespace].respond_to? :to_str
           @namespace = Namespace.new(:uri => opts[:namespace].to_str, opts[:prefix])
         end
       end
     end
   end

I hope you can give me a hint of what the best practice is.

Cheers,
Daniel

2

I hope you can give me a hint of what the best practice is.

I don't know what is the best practice but you can ask ruby

moulon% ruby -e 'a = [1, 2]; b = a.to_a; p a.object_id==b.object_id'
true
moulon%

moulon% ruby -e 'a = "12"; b = a.to_s; p a.object_id==b.object_id'
true
moulon%

Guy Decoux

3

ts wrote:

> I hope you can give me a hint of what the best practice is.

I don't know what is the best practice but you can ask ruby

moulon% ruby -e 'a = [1, 2]; b = a.to_a; p a.object_id==b.object_id'
true
moulon%

moulon% ruby -e 'a = "12"; b = a.to_s; p a.object_id==b.object_id'
true
moulon%

Guy Decoux

Sweet! Thanks!

Cheers,
Daniel

4

Daniel Schierbeck wrote:

ts wrote:

> I hope you can give me a hint of what the best practice is.

I don't know what is the best practice but you can ask ruby

moulon% ruby -e 'a = [1, 2]; b = a.to_a; p a.object_id==b.object_id'
true
moulon%
moulon% ruby -e 'a = "12"; b = a.to_s; p a.object_id==b.object_id'
true
moulon%

Guy Decoux

Sweet! Thanks!

Cheers,
Daniel

Those two examples are returning the same object because it is already in the desired form. If it is actually a change, you will get a new object:

irb(main):001:0> a = 12
=> 12
irb(main):002:0> b = a.to_s
=> "12"
irb(main):003:0> a.object_id
=> 25
irb(main):004:0> b.object_id
=> -605442624

-Justin