Ruby - reference of self in the class method

Question

Went over this code on RubyMonk:

 class Item
   def initialize(item)
     @item = item
   end
   def show
     puts "The item name is: #{self}"
   end
   def to_s
     "#{@item}"
   end
 end

 Item.new("potion").show

The code passes but the use of the self variable is a bit ambiguous to me. You could've easily supplanted to_s with self in the show method and gotten the same results. Can somebody explain the difference between both interpolations and why/how self is used here? Additionally, without the the method to_s, the code returns a proxy. What is the significance of defining the to_s here?

Answer 1

String interpolation implicitly calls the to_s method on an object. So, when you define the to_s method on Item, you are explicitly telling that object how to represent itself with respect to a string. self is used in this case because there is an implicit call to to_s within the interpolation of the Item object. Defining to_s explicitly tells Item how to render itself within a string.

For some additional details, check out this excellent post on explicit vs. implicit conversion methods.