snippet.rb

# `irb` console session.
# Making a class, making it comparable, overriding its display formats, and using map!

# Make a class that mixins Comparable and defines <=> so it gets all <, ==, >, etc.
# Other methods like Array.sort will now work too

>> class Box
>>   def <=>(other)
>>     [source, color] <=> [other.source, other.color]
>>   end
>>   attr_accessor :color, :source
>>   include Comparable
>> end
>> a, b = Box.new, Box.new
=> [#<Box:0x5627dc>, #<Box:0x5627c8>]
>> a.color = 'red'; a.source = 'MN'
=> "MN"
>> b.color = 'red'; b.source = 'MN'
=> "MN"
>> a == b
=> true
>> a.color = 'blue'
=> "blue"
>> a == b
=> false


# Make more boxes and sort dem! AZ (John McCain!) comes first

>> c, d = a.dup, a.dup
=> [#<Box:0x54b5dc @source="MN", @color="blue">, #<Box:0x54b5c8 @source="MN", @color="blue">]
>> c.source = 'AZ'
=> "AZ"
>> boxes = [a,b,c,d]
=> [#<Box:0x5627dc @source="MN", @color="blue">, #<Box:0x5627c8 @source="MN", @color="red">, #<Box:0x54b5dc @source="AZ", @color="blue">, #<Box:0x54b5c8 @source="MN", @color="blue">]
>> boxes.sort 
=> [#<Box:0x54b5dc @source="AZ", @color="blue">, #<Box:0x5627dc @source="MN", @color="blue">, #<Box:0x54b5c8 @source="MN", @color="blue">, #<Box:0x5627c8 @source="MN", @color="red">]


# Now i re-open the Box class and override the inspect method to give a better  output format while programming

>> class Box
>>   def inspect
>>     "<Box #{source} #{color}>"
>>     end
>>   end
=> nil
>> boxes.sort
=> [<Box AZ blue>, <Box MN blue>, <Box MN blue>, <Box MN red>]


# Make a better output format that might be displayed for an end user
>> class Box
>>   def to_s
>>     "#{color} Box from #{source}"
>>     end
>>   end
=> nil
>> puts boxes
blue Box from MN
blue Box from MN
blue Box from AZ
blue Box from MN
>> "I got a #{boxes.join ', '}"
=> "I got a blue Box from MN, blue Box from MN, blue Box from AZ, blue Box from MN"



# Call map to transform each element of boxes
# map! does the same and modifies the elements

>> boxes.map {|b| b.source }
=> ["MN", "MN", "AZ", "MN"]
>> boxes
=> [<Box MN blue>, <Box MN red>, <Box AZ blue>, <Box MN blue>]
>> boxes.map! {|b| b.source }
=> ["MN", "MN", "AZ", "MN"]
>> boxes
=> ["MN", "MN", "AZ", "MN"]