带你读《2022技术人的百宝黑皮书》——淘宝iOS扫一扫架构升级 - 设计模式的应用（5）

@interface TBBaseStateInfo : NSObject { @private
TBBaseState<TBBaseStateDelegate> *_currentState; //记录当前的 State
}
//使用当前的 State 执行
-   (void)performAction;
//更新当前的 State
-   (void)setState:(TBBaseState <TBBaseStateDelegate> *)state;
//获取当前的 State
-   (TBBaseState<TBBaseStateDelegate> *)getState; 
@end

@implementation TBBaseStateInfo
- (void)performAction {
//当前状态开始执行
[_currentState perfromAction:self];
}
-   (void)setState:(TBBaseState <TBBaseStateDelegate> *)state {
_currentState = state;
}
-   (TBBaseState<TBBaseStateDelegate> *)getState { return _currentState;
}
@end

    typedef NS_ENUM(NSInteger, TBStateType) {
    TBStateTypeNormal, //空状态
3TBStateTypeSingleCode, //单码展示态
    TBStateTypeMultiCode, //多码展示态
 };
 
@interface TBStateInfo : TBBaseStateInfo
//以 key-value 的方式存储业务 type 和对应的状态 state
-   (void)setState:(TBBaseState<TBBaseStateDelegate> *)state forType:(TBStateType)type;
//更新 type，并执行 state
-   (void)setType:(TBStateType)type; @end

@implementation TBStateInfo

-   (void)setState:(TBBaseState<TBBaseStateDelegate> *)state forType:(TBStateType)type { [self.stateDict tb_setObject:state forKey:@(type)];
}

-   (void)setType:(TBStateType)type { id oldState = [self getState];
//找到当前能响应的状态
id newState = [self.stateDict objectForKey:@(type)];
//如果状态未发生变更则忽略if (oldState == newState)
return;
if ([newState respondsToSelector:@selector(perfromAction:)]) { [self setState:newState];
//转态基于当前的状态信息开始执行[newState perfromAction:self];
}
}
@end

1   @protocol TBBaseStateDelegate <NSObject>
2   - (void)perfromAction:(TBBaseStateInfo *)stateInfo;
3   @end

@interface TBSingleCodeState : TBBaseState
@end

@implementation TBSingleCodeState

//实现 Protocol
- (void)perfromAction:(TBStateInfo *)stateAction {
//业务逻辑处理 Start
...
//业务逻辑处理 End
}

@end

//状态初始化
- (void)setupState {
TBSingleCodeState *singleCodeState = TBSingleCodeState.new; //单码状态TBNormalState *normalState = TBNormalState.new; //正常状态TBMultiCodeState *multiCodeState = [self getMultiCodeState]; //多码状态
[self.stateInfo setState:normalState forType:TBStateTypeNormal]; [self.stateInfo setState:singleCodeState forType:TBStateTypeSingleCode];
[self.stateInfo setState:multiCodeState forType:TBStateTypeMultiCode];
)
//切换常规状态
- (void)processorA {
//...
[self.stateInfo setType:TBStateTypeNormal];
//...
}

//切换多码状态
- (void)processorB {
//...