Teaching you how to program in Ruby goes beyond the scope of this book, however, this section will show you at least what Ruby code looks like. If you know another programming language already, some things may already be familiar to you. If you don't, hopefully the following code will not appear too intimidating.
1 # This is a comment and will not be executed 2 # by the Ruby interpreter. 3 # 4 # This is not the usual 'Hello World' example, so 5 # don't worry if you don't understand everything. 6 # This example is meant to give you a general feeling 7 # of what it is like to write Ruby programs. 8 9 require 'pathname' # Here we're requiring an external library 10 # which is part of the Ruby Standard Library. 11 12 class FilePrinter 13 14 # Constructor method 15 def initialize(path) 16 # This method expects a valid path, however Ruby is dynamically-typed 17 # so anything can be passed to this method. 18 # To check that the input value is valid, just check if if it behaves 19 # like a path. This is called 'duck typing'. 20 raise RuntimeError, "Invalid path: #{path}" unless path.respond_to? :basename 21 @path = path 22 @name = @path.basename 23 end 24 25 def show 26 # Ruby objects and expressions can be interpolated in strings 27 puts " #@name -- #{@path.stat.size} bytes" 28 end 29 30 end 31 32 class DirPrinter < FilePrinter # Definition of a child class 33 34 def initialize(path) 35 super # Call to the parent's constructur 36 @children = @path.children 37 end 38 39 def show 40 puts " #@name/ -- #{@children.length} item(s)" 41 end 42 43 end 44 45 # No parenthesys are required unless needed! 46 pwd = Pathname.new Dir.pwd 47 48 puts "Current Directory: #{pwd}" 49 50 # Get the children items of the current directory, 51 # select only directories, 52 # sort them alphabetically, 53 # and for each one of them... 54 pwd.children.select{|i| i.directory? }.sort.each do |item| 55 # Call the show method, printing the 56 # directory name and the number of child items 57 DirPrinter.new(item).show 58 end 59 60 pwd.children.select{|i| !i.directory? }.sort.each do |item| 61 FilePrinter.new(item).show 62 end