10. 状态模式

### 10. 状态模式
> 定义：允许对象在内部状态改变时改变它的行为，对象看起来好像修改了它的类。

- 定义又开始模糊了，理一下，当对象的内部状态改变时，它的行为跟随状态的改变而改变了，看起来好像重新初始化了一个类似的。

- 需求：以自动售货机为例（有已投币、未投币等状态和投币、退币等方法）
 - 最初实现待改进的售货机：[VendingMachine.java](https://github.com/youlookwhat/DesignPattern/blob/master/app/src/main/java/com/example/jingbin/designpattern/state/old/VendingMachine.java)
 - 改进后的售货机（更具有延展性）:[VendingMachineBetter.java](https://github.com/youlookwhat/DesignPattern/blob/master/app/src/main/java/com/example/jingbin/designpattern/state/better/VendingMachineBetter.java)

```java
	// 放钱
    public void insertMoney() {
        currentState.insertMoney();
    }
    // 退钱
    public void backMoney() {
        currentState.backMoney();
    }
    // 转动曲柄
    public void turnCrank() {
        currentState.turnCrank();
        if (currentState == soldState || currentState == winnerState) {
            currentState.dispense();//两种情况会出货
        }
    }
    // 出商品
    public void dispense() {
        Log.e("VendingMachineBetter", "---发出一件商品");
        if (count > 0) {
            count--;
        }
    }
    // 设置对应状态
    public void setState(State state) {
        this.currentState = state;
    }
	```

- 状态的接口：[State.java](https://github.com/youlookwhat/DesignPattern/blob/master/app/src/main/java/com/example/jingbin/designpattern/state/better/State.java)
 - 对应状态的接口实现类：
 	- eg: 中奖状态：[WinnerState.java](https://github.com/youlookwhat/DesignPattern/blob/master/app/src/main/java/com/example/jingbin/designpattern/state/better/WinnerState.java)
 	- eg: 售卖状态：[SoldState.java](https://github.com/youlookwhat/DesignPattern/blob/master/app/src/main/java/com/example/jingbin/designpattern/state/better/SoldState.java)
 		
- 改进后的售货机测试：
	
	```java
	// 初始化售货机,且里面有3个商品
   VendingMachineBetter machineBetter = new VendingMachineBetter(3);
   machineBetter.insertMoney();
   machineBetter.turnCrank();
	```