[designmode] Decorator Pattern

Basic introduction

1. Decorator mode ： Dynamically attach new functions to objects . In terms of object function expansion , It's more flexible than inheritance , The decorator pattern also embodies the principle of opening and closing (ocp)

2. The dynamic addition of new functions to objects and ocp principle , In the later application examples, it will be reflected in the form of code , Please pay attention to the experience .

1. Starbucks Coffee order project （ café ）：

1. Types of coffee / Single coffee ：Espresso( Espresso )、ShortBlack、LongBlack( Cafe Americano )、Decaf( No cause coffee )

2. seasoning ：Milk、Soy( Soya-bean milk )、Chocolate

3. When it comes to expanding new types of coffee , It has good expansibility 、 It's easy to change 、 Convenient maintenance

4. Use OO To calculate the cost of different kinds of coffee : Customers can order a single coffee , You can also have coffee alone + Seasoning mix .

2. programme 1- Solve Starbucks Coffee order project

Poor scheme 1

Class diagram ：

3. programme 1- Solve Starbucks Coffee order problem analysis

1. Drink Is an abstract class , It means drink

2. des It's a description of coffee , Like the name of the coffee

3. cost() The way is to calculate the cost ,Drink Class to make an abstract method . 4) Decaf It's a single coffee , Inherit Drink, And implement cost

4. Espres