79 lines
1.5 KiB
Ruby
79 lines
1.5 KiB
Ruby
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# The command pattern is a behavior design pattern used to store the information
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# necessary to call methods at a future time.
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# The command is merely a set of actions wrapped in an object. With ruby, we can
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# use Procs to do the same thing without the need to create a separate object.
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# This is a good option when the action is simple and doesn't require saving
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# state information, otherwise, a command class is the better option.
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# Invoker
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class Switch
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attr_reader :history
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def execute(cmd)
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@history ||= []
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@history << cmd.execute
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end
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end
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# Command Interface
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class Command
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attr_reader :obj
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def initialize(obj)
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@obj = obj
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end
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def execute
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raise NotImplementedError
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end
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end
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# Command for turning on
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class TurnOnCommand < Command
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def execute
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obj.turn_on
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end
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end
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# Command for turning off
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class TurnOffCommand < Command
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def execute
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obj.turn_off
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end
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end
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# Receiver
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class Light
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def turn_on
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'the light is on'
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end
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def turn_off
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'the light is off'
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end
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end
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# Client
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class LightSwitchClient
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attr_reader :switch
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def initialize
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@lamp = Light.new
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@switch = Switch.new
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end
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def switch_for(cmd)
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case cmd
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when 'on' then @switch.execute(TurnOnCommand.new(@lamp))
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when 'off' then @switch.execute(TurnOffCommand.new(@lamp))
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else puts 'Sorry, I so sorry'
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end
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end
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end
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client = LightSwitchClient.new
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client.switch_for('on')
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client.switch_for('off')
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client.switch.history #=> ['the light is on', 'the light is off']
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