63 lines
1.2 KiB
Ruby
63 lines
1.2 KiB
Ruby
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# An object, called the subject, maintains a list of its dependents, called
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# observers, and notifies them automatically of any state changes, usually by
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# calling one of their methods.
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module Observable
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def initialize
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@observers = []
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end
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def add_observer(observer)
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@observers << observer unless @observers.include?(observer)
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end
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def delete_observer(observer)
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@observers.delete(observer)
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end
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def notify_observers
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@observers.each { |x| x.update(self) }
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end
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end
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class Employee
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include Observable
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attr_reader :name
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attr_accessor :title, :salary
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def initialize(name, title, salary)
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super()
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@name, @title, @salary = name, title, salary
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end
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end
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class BaseObserver
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def update
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raise 'Must be implement "update" function'
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end
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end
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class Payroll < BaseObserver
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def update(employee)
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p("Cut a new check for #{employee.name}!")
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p("His salary is now #{employee.salary}!")
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end
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end
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class TaxMan < BaseObserver
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def update(employee)
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p("Send #{employee.name} a new tax bill!")
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end
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end
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# Usage
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mike = Employee.new('Mike', 'project manger', 25000)
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mike.add_observer(Payroll.new)
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mike.add_observer(TaxMan.new)
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mike.salary = 35000
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mike.title = 'senior project manger'
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mike.notify_observers
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