Ruby: Module, Mixins and Blocks confusing?

Question

Following is the code I tried to run from the Ruby Programming Book http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_modules.html

Why doesn\'t the

Answer 1

The following code is not very elaborated. Just to show you that today you already have means, like the hooks called by Ruby when certain events occur, to check which method (from the including class or the included module) will be used/not used.

module Inject
    def self.append_features(p_host) # don't use included, it's too late
        puts "#{self} included into #{p_host}"
        methods_of_this_module = self.instance_methods(false).sort
        print "methods of #{self} : "; p methods_of_this_module
        first_letter = []
        methods_of_this_module.each do |m|
            first_letter << m[0, 2]
        end
        print 'selection to reduce the display : '; p first_letter
        methods_of_host_class = p_host.instance_methods(true).sort
        subset = methods_of_host_class.select { |m| m if first_letter.include?(m[0, 2]) }
        print "methods of #{p_host} we are interested in: "; p subset
        methods_of_this_module.each do |m|
            puts "#{self.name}##{m} will not be used" if methods_of_host_class.include? m
        end

        super # <-- don't forget it !
    end

Rest as in your post. Execution :

$ ruby -v
ruby 1.8.6 (2010-09-02 patchlevel 420) [i686-darwin12.2.0]
$ ruby -w tinject.rb 
Inject included into Array
methods of Inject : ["inject", "product", "sum"]
selection to reduce the display : ["in", "pr", "su"]
methods of Array we are interested in: ["include?", "index",  
 ..., "inject", "insert", ..., "instance_variables", "private_methods", "protected_methods"]
Inject#inject will not be used
$ rvm use 1.9.2
...
$ ruby -v
ruby 1.9.2p320 (2012-04-20 revision 35421) [x86_64-darwin12.2.0]
$ ruby -w tinject.rb 
Inject included into Array
methods of Inject : [:inject, :product, :sum]
selection to reduce the display : ["in", "pr", "su"]
methods of Array we are interested in: [:include?, :index, ..., :inject, :insert, 
..., :private_methods, :product, :protected_methods]
Inject#inject will not be used
Inject#product will not be used