Builder pattern

Builder pattern (Builder Pattern) Also called generator mode , It's a bit like the factory model , Both use special classes to create objects .

• The factory pattern is used to create a series of related but different objects .
• The builder pattern is used to create a type of complex object , By setting different optional parameters , Customize to create different objects .

The main difference is that the builder pattern focuses on building a complex object step by step , And the abstract factory pattern focuses on multiple series of product objects .

Why use builder mode

• A class has many properties , Constructor and arguments are too long .
• There are certain dependencies and constraints between attributes .
• The creation of objects needs to follow a certain sequence or steps

There is a sentence that sums up the builder model very well ：

When we want to create an object composed of multiple parts , And their construction needs to be done step by step , Only when all parts are created , This object is complete .

That's exactly what it is. Where the builder's design pattern can be used .

The advantages and disadvantages of the builder model

advantage

1. Independence of builders , Easy to expand .
2. Easy to control detail risk .
3. Decouple the construction and presentation of objects

shortcoming

1. Products must have something in common , The scope is limited .
2. If the internal changes are complex , There will be a lot of construction classes .

The composition of the builder model

1. The actual object ： The actual object to return
2. Builder abstract class ： Define the functions that the builder entity class needs to implement .
3. Builder entity class ： Inherit builder abstract class , Concrete implementation of abstract class methods .
4. Director class ：