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Ruby.in.20.minutes.md

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=begin

Ruby in Twenty Minutes

Can run this Markdown file for output of code-examples via Ruby or IRB without any change.

Simple Tasks

=end

print "3+2 -> ",3+2,"\n"
print "3*2 -> ",3*2,"\n"
print "3**2 -> ",3**2,"\n"
print "Math.sqrt(9)-> ",Math.sqrt(9),"\n" # built-in module: Math

=begin

Methods

=end

# simple method
def what_ruby
  print RUBY_RELEASE_DATE," | ",RUBY_PLATFORM,"\n"
  RUBY_VERSION
end
# can call with/out paranthesis
what_ruby == what_ruby()

# method with a param
def ruby_version(ver)
  print "ruby #{ver}\n" # string interpolation
end
# calling methods with params within paranthesis
ruby_version(what_ruby)
# calling methods with params without paranthesis
ruby_version what_ruby

# method with default param value
def ruby_detail(key="description", val=RUBY_DESCRIPTION)
  print "[#{key}:] #{val}\n"
end

ruby_detail
ruby_detail("Ruby Description")
ruby_detail "copyright", RUBY_COPYRIGHT

=begin

Class

=end

class Chruby def initialize(name="ruby", version="2.2.3") @name = name @version = version end

def change(name, version) @name = name @version = version print "changing ruby to #{@name}-#{@version}\n" end

def install() print "installing #{@name}-#{@version}\n" end end

chruby = Chruby.new() chruby.install

chjruby = Chruby.new chjruby.change "jruby", "1.9.3" chjruby.install

print "instance_methods (all from now and ancestor classes): #{Chruby.instance_methods}\n"

print "instance_methods (just the methods defined for Chruby): #{Chruby.instance_methods(false)}\n"

checking what attribute and methods defined for every object

print "does chjruby responds to 'name': #{chjruby.respond_to?("name")}\n" print "does chjruby responds to 'install': #{chjruby.respond_to?("install")}\n"

=begin


* with attr_accessor
=end

class Chruby
  attr_accessor :name
end

chmri = Chruby.new("mri")
print "#{chmri.name}\n"

## checking if 'name' is available now that an attribute-accessor has been provided
print "does chjruby responds to 'name': #{chjruby.respond_to?("name")}\n"
print "does chjruby responds to 'name=': #{chjruby.respond_to?("name=")}\n"

=begin
  • More responsible Class =end

class Chrubies attr_accessor :name, :versions

def initialize(name="ruby", version="2.2.3") @name = name @versions = versions end

def change(name, version) if version.nil? or name.nil? ## 'if' conditionals print "ruby or version detail is missing" return end if @versions.respond_to?("each") unless @versions.include? version ## inverse of 'if' condition puts "given '#{version}' version doesn't belong to this '#{@versions.join(', ')}' chrubies set" return end elsif version != @versions puts "given '#{version}' version doesn't belong to this '#{@versions}' chruby" return end if name != @name puts "given '#{name}' ruby doesn't belong to this '#{@name}' chruby" return end self.install print "changing ruby to #{@name}-#{@versions}\n" end

def install() if versions.nil? or name.nil? puts "no ruby desired for installation" elsif versions.respond_to?("each") @versions.each do |version| ## looping if object responds to 'each' puts "installing #{@name}-#{version}" end else puts "installing #{@name}-#{@versions}" end end end

=begin


* Running block only if Ruby script is called directly
=end

if __FILE__ == $0
  jrb = Chrubies.new
  jrb.install
  jrb.change "jruby", "1.9.3"

  jrb.name = "jruby"
  jrb.change "jruby", "1.9.3"

  jrb.versions = "2.2.3"
  jrb.change "jruby", "1.9.3"

  jrb.versions = ["1.9.3","2.2.3"]
  jrb.change "jruby", "1.9.3"

  jrb.change "ruby", "1.9.3"
end

=begin
  • Can use more traditional looping when don't have an object to loop around =end

for index in 1..3 puts "element #{index} of 3" end

=begin

Lot more to explore

  • different control structures
  • use of blocks and 'yield'
  • modules

=end