# 装饰模式

## 一句话



In plain words 通俗易懂

> Decorator pattern lets you dynamically change the behavior of an object at run time by wrapping them in an object of a decorator class.
> Decorator 模式允许您通过将对象包装在 Decorator 类的对象中，在运行时动态更改对象的行为。

> 

**Programmatic Example 编程示例**

Lets take coffee for example. First of all we have a simple coffee implementing the coffee interface
让我们以咖啡为例。首先，我们有一个简单的 coffee 实现 coffee 接口

```php
interface Coffee
{
    public function getCost();
    public function getDescription();
}

class SimpleCoffee implements Coffee
{
    public function getCost()
    {
        return 10;
    }

    public function getDescription()
    {
        return 'Simple coffee';
    }
}
```



We want to make the code extensible to allow options to modify it if required. Lets make some add-ons (decorators)
我们希望使代码可扩展，以允许选项在需要时对其进行修改。让我们制作一些附加组件（装饰器）

```php
class MilkCoffee implements Coffee
{
    protected $coffee;

    public function __construct(Coffee $coffee)
    {
        $this->coffee = $coffee;
    }

    public function getCost()
    {
        return $this->coffee->getCost() + 2;
    }

    public function getDescription()
    {
        return $this->coffee->getDescription() . ', milk';
    }
}

class WhipCoffee implements Coffee
{
    protected $coffee;

    public function __construct(Coffee $coffee)
    {
        $this->coffee = $coffee;
    }

    public function getCost()
    {
        return $this->coffee->getCost() + 5;
    }

    public function getDescription()
    {
        return $this->coffee->getDescription() . ', whip';
    }
}


```







## 缺点



- 产生很多小对象，影响程序性能

- 比继承更加容易出错，排错也更难







# 外观模式

## 一句话



Wikipedia says 维基百科说

> A facade is an object that provides a simplified interface to a larger body of code, such as a class library.
> Facade 是一个对象，它为较大的代码体（如类库）提供简化的接口。







Here we have the facade
这里有门面

```
class ComputerFacade
{
    protected $computer;

    public function __construct(Computer $computer)
    {
        $this->computer = $computer;
    }

    public function turnOn()
    {
        $this->computer->getElectricShock();
        $this->computer->makeSound();
        $this->computer->showLoadingScreen();
        $this->computer->bam();
    }

    public function turnOff()
    {
        $this->computer->closeEverything();
        $this->computer->pullCurrent();
        $this->computer->sooth();
    }
}
```



Now to use the facade
现在使用 Facade

```
$computer = new ComputerFacade(new Computer());
$computer->turnOn(); // Ouch! Beep beep! Loading.. Ready to be used!
$computer->turnOff(); // Bup bup buzzz! Haah! Zzzzz
```