Ruby 外观模式讲解和代码示例

# The Facade class provides a simple interface to the complex logic of one or # several subsystems. The Facade delegates the client requests to the # appropriate objects within the subsystem. The Facade is also responsible for # managing their lifecycle. All of this shields the client from the undesired # complexity of the subsystem. class Facade # Depending on your application's needs, you can provide the Facade with # existing subsystem objects or force the Facade to create them on its own. def initialize(subsystem1, subsystem2) @subsystem1 = subsystem1 || Subsystem1.new @subsystem2 = subsystem2 || Subsystem2.new end # The Facade's methods are convenient shortcuts to the sophisticated # functionality of the subsystems. However, clients get only to a fraction of # a subsystem's capabilities. def operation results = [] results.append('Facade initializes subsystems:') results.append(@subsystem1.operation1) results.append(@subsystem2.operation1) results.append('Facade orders subsystems to perform the action:') results.append(@subsystem1.operation_n) results.append(@subsystem2.operation_z) results.join("\n") end end # The Subsystem can accept requests either from the facade or client directly. # In any case, to the Subsystem, the Facade is yet another client, and it's not # a part of the Subsystem. class Subsystem1 # @return [String] def operation1 'Subsystem1: Ready!' end # ... # @return [String] def operation_n 'Subsystem1: Go!' end end # Some facades can work with multiple subsystems at the same time. class Subsystem2 # @return [String] def operation1 'Subsystem2: Get ready!' end # ... # @return [String] def operation_z 'Subsystem2: Fire!' end end # The client code works with complex subsystems through a simple interface # provided by the Facade. When a facade manages the lifecycle of the subsystem, # the client might not even know about the existence of the subsystem. This # approach lets you keep the complexity under control. def client_code(facade) print facade.operation end # The client code may have some of the subsystem's objects already created. In # this case, it might be worthwhile to initialize the Facade with these objects # instead of letting the Facade create new instances. subsystem1 = Subsystem1.new subsystem2 = Subsystem2.new facade = Facade.new(subsystem1, subsystem2) client_code(facade) 

Facade initializes subsystems: Subsystem1: Ready! Subsystem2: Get ready! Facade orders subsystems to perform the action: Subsystem1: Go! Subsystem2: Fire!