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外观

外观在 Ruby 中的实现

外观是一种结构型设计模式,能为复杂系统、程序库或框架提供一个简单(但有限)的接口。

尽管外观模式降低了程序的整体复杂度,但它同时也有助于将不需要的依赖移动到同一个位置。

进一步了解外观模式

在 Ruby 中使用模式

复杂度:

流行度:

使用示例:使用 Ruby 开发的程序中会经常使用外观模式。它在与复杂程序库和 API 协作时特别有用。

识别方法:外观可以通过使用简单接口,但将绝大部分工作委派给其他类的类来识别。通常情况下,外观管理其所使用的对象的完整生命周期。

概念示例

本例说明了外观设计模式的结构并重点回答了下面的问题:

  • 它由哪些类组成?
  • 这些类扮演了哪些角色?
  • 模式中的各个元素会以何种方式相互关联?

main.rb: 概念示例

# 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)

output.txt: 执行结果

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

外观在其他编程语言中的实现

外观 在 Java 中的实现 外观 在 C# 中的实现 外观 在 PHP 中的实现 外观 在 Python 中的实现 外观 在 Swift 中的实现 外观 在 TypeScript 中的实现