1. 設(shè)計(jì)模式原理說(shuō)明

裝飾模式（Decorator Pattern） 是一種結(jié)構(gòu)型設(shè)計(jì)模式，它允許在不改變對(duì)象接口的前提下，動(dòng)態(tài)地給對(duì)象增加額外的責(zé)任或功能。這種模式創(chuàng)建了一個(gè)裝飾類(lèi)，用于包裝原有的類(lèi)，并在保持類(lèi)方法簽名完整性的前提下，提供了額外的功能。

主要角色

1. Component（組件）：定義了一個(gè)對(duì)象接口，可以給這些對(duì)象動(dòng)態(tài)地添加職責(zé)。
2. ConcreteComponent（具體組件）：定義了一個(gè)具體的對(duì)象，也可以給這個(gè)對(duì)象添加一些責(zé)任。
3. Decorator（裝飾器）：持有一個(gè)?Component?對(duì)象的實(shí)例，并定義了一個(gè)與?Component?接口一致的接口。
4. ConcreteDecorator（具體裝飾器）：向組件添加新的責(zé)任，通常通過(guò)在其前后添加行為來(lái)實(shí)現(xiàn)。

2. UML 類(lèi)圖及解釋

UML 類(lèi)圖

+-----------------+                +-----------------+
|    Component    |                | ConcreteComponent|
|-----------------|                |-----------------|
| + operation(): void|             | + operation(): void|
+-----------------+                +-----------------+^                             ^|                             ||                             |v                             v
+-----------------+
|    Decorator    |
|-----------------|
| - component: Component  |
| + setComponent(component: Component)|
| + operation(): void            |
+-----------------+^||v
+-----------------+                +-----------------+
| ConcreteDecoratorA|             | ConcreteDecoratorB|
|-----------------|                |-----------------|
| + operation(): void|             | + operation(): void|
| + addedBehavior(): void|         | + addedBehavior(): void|
+-----------------+                +-----------------+

類(lèi)圖解釋

• Component：定義了一個(gè)對(duì)象接口，可以給這些對(duì)象動(dòng)態(tài)地添加職責(zé)。
• ConcreteComponent：定義了一個(gè)具體的對(duì)象，也可以給這個(gè)對(duì)象添加一些責(zé)任。
• Decorator：持有一個(gè)?Component?對(duì)象的實(shí)例，并定義了一個(gè)與?Component?接口一致的接口。裝飾器可以在其前后添加行為。
• ConcreteDecoratorA?和?ConcreteDecoratorB：具體裝飾器，向組件添加新的責(zé)任，通常通過(guò)在其前后添加行為來(lái)實(shí)現(xiàn)。

3. 代碼案例及邏輯詳解

Java 代碼案例

// 組件接口
interface Component {void operation();
}// 具體組件
class ConcreteComponent implements Component {@Overridepublic void operation() {System.out.println("ConcreteComponent operation");}
}// 裝飾器
abstract class Decorator implements Component {protected Component component;public void setComponent(Component component) {this.component = component;}@Overridepublic void operation() {if (component != null) {component.operation();}}
}// 具體裝飾器 A
class ConcreteDecoratorA extends Decorator {@Overridepublic void operation() {super.operation();addedBehavior();}private void addedBehavior() {System.out.println("ConcreteDecoratorA added behavior");}
}// 具體裝飾器 B
class ConcreteDecoratorB extends Decorator {@Overridepublic void operation() {super.operation();addedBehavior();}private void addedBehavior() {System.out.println("ConcreteDecoratorB added behavior");}
}// 客戶(hù)端
public class Client {public static void main(String[] args) {Component component = new ConcreteComponent();ConcreteDecoratorA decoratorA = new ConcreteDecoratorA();ConcreteDecoratorB decoratorB = new ConcreteDecoratorB();decoratorA.setComponent(component);decoratorB.setComponent(decoratorA);decoratorB.operation();// 輸出:// ConcreteComponent operation// ConcreteDecoratorA added behavior// ConcreteDecoratorB added behavior}
}

C++ 代碼案例

#include <iostream>// 組件接口
class Component {
public:virtual void operation() = 0;virtual ~Component() {}
};// 具體組件
class ConcreteComponent : public Component {
public:void operation() override {std::cout << "ConcreteComponent operation" << std::endl;}
};// 裝飾器
class Decorator : public Component {
protected:Component* component;public:void setComponent(Component* component) {this->component = component;}void operation() override {if (component != nullptr) {component->operation();}}
};// 具體裝飾器 A
class ConcreteDecoratorA : public Decorator {
public:void operation() override {Decorator::operation();addedBehavior();}void addedBehavior() {std::cout << "ConcreteDecoratorA added behavior" << std::endl;}
};// 具體裝飾器 B
class ConcreteDecoratorB : public Decorator {
public:void operation() override {Decorator::operation();addedBehavior();}void addedBehavior() {std::cout << "ConcreteDecoratorB added behavior" << std::endl;}
};// 客戶(hù)端
int main() {Component* component = new ConcreteComponent();Decorator* decoratorA = new ConcreteDecoratorA();Decorator* decoratorB = new ConcreteDecoratorB();decoratorA->setComponent(component);decoratorB->setComponent(decoratorA);decoratorB->operation();// 輸出:// ConcreteComponent operation// ConcreteDecoratorA added behavior// ConcreteDecoratorB added behaviordelete component;delete decoratorA;delete decoratorB;return 0;
}

Python 代碼案例

from abc import ABC, abstractmethod# 組件接口
class Component(ABC):@abstractmethoddef operation(self):pass# 具體組件
class ConcreteComponent(Component):def operation(self):print("ConcreteComponent operation")# 裝飾器
class Decorator(Component):def __init__(self, component: Component):self._component = componentdef operation(self):if self._component:self._component.operation()# 具體裝飾器 A
class ConcreteDecoratorA(Decorator):def operation(self):super().operation()self.added_behavior()def added_behavior(self):print("ConcreteDecoratorA added behavior")# 具體裝飾器 B
class ConcreteDecoratorB(Decorator):def operation(self):super().operation()self.added_behavior()def added_behavior(self):print("ConcreteDecoratorB added behavior")# 客戶(hù)端
if __name__ == "__main__":component = ConcreteComponent()decorator_a = ConcreteDecoratorA(component)decorator_b = ConcreteDecoratorB(decorator_a)decorator_b.operation()# 輸出:# ConcreteComponent operation# ConcreteDecoratorA added behavior# ConcreteDecoratorB added behavior

Go 代碼案例

package mainimport "fmt"// 組件接口
type Component interface {Operation()
}// 具體組件
type ConcreteComponent struct{}func (c *ConcreteComponent) Operation() {fmt.Println("ConcreteComponent operation")
}// 裝飾器
type Decorator struct {component Component
}func (d *Decorator) SetComponent(component Component) {d.component = component
}func (d *Decorator) Operation() {if d.component != nil {d.component.Operation()}
}// 具體裝飾器 A
type ConcreteDecoratorA struct {Decorator
}func (c *ConcreteDecoratorA) Operation() {c.Decorator.Operation()c.AddedBehavior()
}func (c *ConcreteDecoratorA) AddedBehavior() {fmt.Println("ConcreteDecoratorA added behavior")
}// 具體裝飾器 B
type ConcreteDecoratorB struct {Decorator
}func (c *ConcreteDecoratorB) Operation() {c.Decorator.Operation()c.AddedBehavior()
}func (c *ConcreteDecoratorB) AddedBehavior() {fmt.Println("ConcreteDecoratorB added behavior")
}// 客戶(hù)端
func main() {component := &ConcreteComponent{}decoratorA := &ConcreteDecoratorA{Decorator: Decorator{component: component}}decoratorB := &ConcreteDecoratorB{Decorator: Decorator{component: decoratorA}}decoratorB.Operation()// 輸出:// ConcreteComponent operation// ConcreteDecoratorA added behavior// ConcreteDecoratorB added behavior
}

4. 總結(jié)

裝飾模式 是一種結(jié)構(gòu)型設(shè)計(jì)模式，它允許在不改變對(duì)象接口的前提下，動(dòng)態(tài)地給對(duì)象增加額外的責(zé)任或功能。這種模式通過(guò)創(chuàng)建裝飾類(lèi)來(lái)包裝原有類(lèi)，并在保持類(lèi)方法簽名完整性的前提下，提供了額外的功能。

主要優(yōu)點(diǎn)

1. 靈活性：可以在運(yùn)行時(shí)動(dòng)態(tài)地添加或刪除對(duì)象的責(zé)任，而不需要修改現(xiàn)有的代碼。
2. 可擴(kuò)展性：可以很容易地通過(guò)組合不同的裝飾器來(lái)實(shí)現(xiàn)復(fù)雜的功能。
3. 符合開(kāi)閉原則：可以在不修改現(xiàn)有代碼的情況下，通過(guò)添加新的裝飾器來(lái)擴(kuò)展功能。

主要缺點(diǎn)

1. 增加了系統(tǒng)的復(fù)雜性：裝飾模式會(huì)引入許多小類(lèi)，這可能會(huì)使系統(tǒng)的設(shè)計(jì)變得更復(fù)雜。
2. 調(diào)試?yán)щy：由于裝飾器可以層層嵌套，調(diào)試時(shí)可能難以跟蹤到最終的行為。

適用場(chǎng)景

• 當(dāng)需要在運(yùn)行時(shí)動(dòng)態(tài)地給對(duì)象添加功能時(shí)。
• 當(dāng)需要擴(kuò)展類(lèi)的功能，但又不想使用繼承的方式時(shí)。
• 當(dāng)系統(tǒng)需要提供多種可選功能，且這些功能可以自由組合時(shí)。