Creating a modified capitalize method in Ruby from scratch

Question

I am learning methods in Ruby and thought that the best way to learn them was to create a method that already exists. However, there are two problems that I am running in to:

1. I do not know what the capitalize method looks like
2. My solution (it does more than the original method does) seems like it can be refactored into something more elegant.

This is what I have come up with:

# method that capitalizes a word
def new_capitalize(string)
  if string[0].downcase == "m" && string[1].downcase == "c"
    puts "#{string[0].upcase}#{string[1].downcase}#{string[2].upcase}#{string[3..-1].downcase}"
  else
    puts "#{string[0].upcase}#{string[1..-1].downcase}"
  end
end

name1 = "ryan"
name2 = "jane"

new_capitalize(name1) # prints "Ryan"
new_capitalize(name2) # prints "Jane"

str = "mCnealy"
puts str.capitalize 
       # prints "Mcnealy"

new_capitalize(str) 
       # prints "McNealy"

It seems as if the first part of my if statement could be made much more efficient. It does not need to be even close to my solution as long as it prints the second capital if the name begins with "mc"

Also, if someone could point me to where the built in capitalize method's code could be found that would be great too!

Thank you in advance!

Answer 1

Alright, how about:

module NameRules
  refine String do
    def capitalize
      if self[0..1].downcase == 'mc'
        "Mc#{self[2..-1].capitalize}"
      else
        super
      end
    end
  end
end

Then to use it:

class ThingWithNames
  using NameRules

  def self.test(string)
   string.capitalize
  end
end

ThingWithNames.test('mclemon') # => "McLemon"
ThingWithNames.test('lemon') # => "Lemon"

If we were starting from scratch and not using the C implemented code:

module NameRules
  refine String do
    def capitalize
      if self[0..1].downcase == 'mc'
        "Mc#{self[2..-1].capitalize}"
      else
        new_string = self.downcase
        new_string[0] = new_string[0].upcase
        new_string
      end
    end
  end
end

Reference materials:

String#capitalize source
A really good presentation on refinements