97 lines
2.0 KiB
Ruby
97 lines
2.0 KiB
Ruby
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# The principle states that a client should not be forced to depend on methods
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# that it does not use
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# In this example, there are Computer, Programmer and Technician classes. Both,
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# Programmer and Technician use the Computer in a different way. The programmer
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# uses the computer for typing, but the technician knows how to change the
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# computer hard drive. What Interface Segregation Principle (ISP) enforces is
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# that one class should not depend on methods it does not use.
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# In our case, Programmer is unnecessarily coupled to the
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# Computer#change_hard_drive method because it does not use it, but the state
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# changes that this method enforces can affect the Programmer. Let's refactor
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# the code to obey the LSP.
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class Computer
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def turn_on
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# Implementation
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end
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def type
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# Implementation
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end
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def change_hard_drive
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# Implementation
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end
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end
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class User
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attr_reader :computer
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def initialize(computer)
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@computer = computer
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end
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end
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class Programmer < User
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def use_computer
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computer.turn_on
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computer.type
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end
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end
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class Technician < User
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def fix_computer
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computer.change_hard_drive
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end
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end
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# Solution
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# After this refactor the Technician uses a different object from the type
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# ComputerInternals which is isolated from the state of the Computer. The state
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# of the Computer object can be influenced by the Programmer but the changes
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# wont affect the Technician in any way.
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class Computer
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def turn_on
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# Implementation
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end
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def type
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# Implementation
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end
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end
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class ComputerInternals
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def change_hard_drive
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# Implementation
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end
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end
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class Programmer
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attr_reader :computer
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def initialize(computer)
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@computer = computer
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end
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def use_computer
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computer.turn_on
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computer.type
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end
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end
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class Technician
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attr_reader :computer_internals
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def initialize(computer_internals)
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@computer_internals = computer_internals
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end
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def fix_computer
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computer_internals.change_hard_drive
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end
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end
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