Builder: Problem
Example: a complex object that requires laborious, step-by-step initialization of many fields and nested objects
一个复杂对象的创建通常由多个部分组成，这些部分的组合经常变化
Builder: Solution
Extract the object construction code out of its own class and move it to separate objects called builders
Further extract the series of calls to the builder steps into a separate class called director
进一步将对构建器步骤的一系列调用提取到一个名为 director 的单独类中
– The director defines the order in which to execute the building steps, while the builder provides concrete implementation
– Having a director class is not strictly necessary
– Might be a good place to put various construction routines for reuse
– Completely hiding the details of construction from the client code
– director 定义执行构建步骤的顺序，而构建器提供具体的实现
– 拥有一个 director 类并不是绝对必要的
– 可能是放置各种构建例程以供重用的好地方
– 在客户端代码中完全隐藏构建细节
Builder: Implementation
- Clearly define the common construction steps for building all available product representations
- Declare these steps in the base builder interface
- Create a concrete builder class for each of the product representations and implement their construction steps, and also implement a method for fetching the result of construction
- Consider creating a director class (not necessarily)
- The client code creates both the builder and the director objects
- The construction result can be obtained directly from the director only if all products follow the same interface; otherwise, the client should fetch the result from the builder
1.明确定义构建所有可用产品表示的常见构建步骤
2.在 base builder 界面中声明这些步骤
3.为每个产品表示创建一个具体的 builder 类并实现它们的构造步骤，并实现一个获取构造结果的方法
4.考虑创建一个 director 类（不一定）
5.客户端代码会同时创建 builder 和 director 对象
6.只有当所有产品都遵循相同的接口时，才能直接从 director 获得构造结果;否则，客户端应从生成器中获取结果
Prototype: Problem and Solution
Problem: creating an exact copy of an object
问题：创建对象的精确副本
– Some fields may not be visible from the outside
– The code becomes dependent on that class
– Sometimes you only know the interface but not the concrete class
– 某些字段可能从外部不可见
– 代码变得依赖于该类
– 有时您只知道接口，而不知道具体的类
Solution: the Prototype pattern
– Delegating the cloning process to the actual objects being cloned
– A common interface for all objects supporting cloning, with a singleclone method
– An object supporting cloning is called a prototype
– 将克隆过程委托给正在克隆的实际对象
– 支持克隆的所有对象的通用接口，具有单个
– 支持克隆的对象称为原型
Prototype: Example
Produce exact copies of geometric objects, without coupling the code to their classes
生成几何对象的精确副本，而无需将代码耦合到其类
Note: a subclass may call the parent’s cloning method before copying its own field values to the resulting object.
注意：子类可以调用父级的克隆方法将自己的 Field 值复制到结果对象中。