Ruby 抽象工厂模式讲解和代码示例
抽象工厂是一种创建型设计模式， 它能创建一系列相关的对象， 而无需指定其具体类。
抽象工厂定义了用于创建不同产品的接口， 但将实际的创建工作留给了具体工厂类。 每个工厂类型都对应一个特定的产品变体。
在创建产品时， 客户端代码调用的是工厂对象的构建方法， 而不是直接调用构造函数 （ new操作符）。 由于一个工厂对应一种产品变体， 因此它创建的所有产品都可相互兼容。
客户端代码仅通过其抽象接口与工厂和产品进行交互。 该接口允许同一客户端代码与不同产品进行交互。 你只需创建一个具体工厂类并将其传递给客户端代码即可。
如果你不清楚工厂、 工厂方法和抽象工厂模式之间的区别， 请参阅工厂模式比较。
复杂度：
流行度：
使用示例： 抽象工厂模式在 Ruby 代码中很常见。 许多框架和程序库会将它作为扩展和自定义其标准组件的一种方式。
识别方法： 我们可以通过方法来识别该模式——其会返回一个工厂对象。 接下来， 工厂将被用于创建特定的子组件。
概念示例
本例说明了抽象工厂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 Abstract Factory interface declares a set of methods that return different
# abstract products. These products are called a family and are related by a
# high-level theme or concept. Products of one family are usually able to
# collaborate among themselves. A family of products may have several variants,
# but the products of one variant are incompatible with products of another.
class AbstractFactory
# @abstract
def create_product_a
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# @abstract
def create_product_b
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Factories produce a family of products that belong to a single
# variant. The factory guarantees that resulting products are compatible. Note
# that signatures of the Concrete Factory's methods return an abstract product,
# while inside the method a concrete product is instantiated.
class ConcreteFactory1 < AbstractFactory
def create_product_a
ConcreteProductA1.new
end
def create_product_b
ConcreteProductB1.new
end
end
# Each Concrete Factory has a corresponding product variant.
class ConcreteFactory2 < AbstractFactory
def create_product_a
ConcreteProductA2.new
end
def create_product_b
ConcreteProductB2.new
end
end
# Each distinct product of a product family should have a base interface. All
# variants of the product must implement this interface.
class AbstractProductA
# @abstract
#
# @return [String]
def useful_function_a
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Products are created by corresponding Concrete Factories.
class ConcreteProductA1 < AbstractProductA
def useful_function_a
'The result of the product A1.'
end
end
class ConcreteProductA2 < AbstractProductA
def useful_function_a
'The result of the product A2.'
end
end
# Here's the the base interface of another product. All products can interact
# with each other, but proper interaction is possible only between products of
# the same concrete variant.
class AbstractProductB
# Product B is able to do its own thing...
def useful_function_b
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# ...but it also can collaborate with the ProductA.
#
# The Abstract Factory makes sure that all products it creates are of the same
# variant and thus, compatible.
def another_useful_function_b(_collaborator)
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Products are created by corresponding Concrete Factories.
class ConcreteProductB1 < AbstractProductB
# @return [String]
def useful_function_b
'The result of the product B1.'
end
# The variant, Product B1, is only able to work correctly with the variant,
# Product A1. Nevertheless, it accepts any instance of AbstractProductA as an
# argument.
def another_useful_function_b(collaborator)
result = collaborator.useful_function_a
"The result of the B1 collaborating with the (#{result})"
end
end
class ConcreteProductB2 < AbstractProductB
# @return [String]
def useful_function_b
'The result of the product B2.'
end
# The variant, Product B2, is only able to work correctly with the variant,
# Product A2. Nevertheless, it accepts any instance of AbstractProductA as an
# argument.
def another_useful_function_b(collaborator)
result = collaborator.useful_function_a
"The result of the B2 collaborating with the (#{result})"
end
end
# The client code works with factories and products only through abstract types:
# AbstractFactory and AbstractProduct. This lets you pass any factory or product
# subclass to the client code without breaking it.
def client_code(factory)
product_a = factory.create_product_a
product_b = factory.create_product_b
puts product_b.useful_function_b
puts product_b.another_useful_function_b(product_a)
end
# The client code can work with any concrete factory class.
puts 'Client: Testing client code with the first factory type:'
client_code(ConcreteFactory1.new)
puts "\n"
puts 'Client: Testing the same client code with the second factory type:'
client_code(ConcreteFactory2.new)
output.txt: 执行结果
Client: Testing client code with the first factory type:
The result of the product B1.
The result of the B1 collaborating with the (The result of the product A1.)
Client: Testing the same client code with the second factory type:
The result of the product B2.
The result of the B2 collaborating with the (The result of the product A2.)
