某硬件项目蓝牙管理类VBBluetoothManager重构

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业务背景

正如上篇iOS端智能硬件BLE通信技术实现一文所述，整个蓝牙库的最初设计实现最初都是为硬件通信服务的，19年年前突然接到需求，希望通过车载上放置的蓝牙收音设备，让用户在唤醒设备后，直接将用户的语音指令转成app里面可执行的操作，如“XXX, 播放每日XX的歌”，“XXX，上/下一首”等一些当前app用户常用的操作，产品希望通过这类车载设备来扩大app现有用户的使用场景甚至探寻增加新用户的可能。

现有问题

其实原app中蓝牙通信目前已经有两套代码了，一套用于早先的蓝牙耳机，一套用于硬件A业务，硬件A业务由于是18年11月才并入现有app的，存在两套代码也无可厚非，现在又增加了新的车载设备，难道再编写一套为车载设备而设计的蓝牙通信方案吗？作为一个有节操的程序媛，当然不可能这么做了！！
首先跟嵌入式端同学约定：车载设备的通信协议复用原有硬件A的那一套，这样数据收发处理（发送拆包接收组包）的代码就能复用，但是负责管理蓝牙一系列通信行为（扫描、停止扫描、连接、发现服务、断开连接、接收蓝牙数据等）以及提供发送数据接口和回调收到的数据给用户的VBBluetoothManager类, 耦合了扫描硬件A的标识符serviceUUID, 读写硬件A特征值的标识符characteristicUUID, 甚至有在已扫描到的设备列表中根据硬件名称或UUID查找特定设备的接口，其中的很多接口都是为硬件A通信服务的，先看下原有部分代码：

// from VBBluetoothManager.m, 以下...表示省略其他无关代码
@interface VBBluetoothManager ()
{
    ...
    NSArray *_serviceUUIDs;
    NSMutableArray *_characterUUIDs;
    ...
}

@implementation VBBluetoothManager

- (instancetype)init {
    if (self = [super init]) {
        ...
        _serviceUUIDs = @[[VBUUIDUtil UUIDWithType:VBUUIDService]];
        _characterUUIDs = [NSMutableArray array];
        NSArray *cases = [VBUUIDUtil cases];
        for (NSNumber *type in cases) {
            if ([type integerValue] != VBUUIDService) {
                [_characterUUIDs addObject:[VBUUIDUtil UUIDWithType:[type integerValue]]];
            }
        }
        ...
    }
    return self;
}

#pragma mark - Public Methods

// 扫描外设
- (void)scanWithDurationWithTimeout:(NSTimeInterval)timeout resetPrevScan:(BOOL)isReset {
    if (isReset) {
        [self resetScan];
    }
    // 前台时不指定serviceUUID去扫描（兼容嵌入式旧版本，旧版本蓝牙名称很长，超过了蓝牙广播包的长度限制，导致根据serviceUUID无法扫描到）
    // 后台的话bluetooth state reservation and restoration要求一定要指定serviceUUID
    NSArray *services = ([UIApplication sharedApplication].applicationState == UIApplicationStateActive) ? nil : _serviceUUIDs;
    [_central scanForPeripheralsWithServices: services options:@{CBCentralManagerScanOptionAllowDuplicatesKey: @NO}];
    // 先将之前的扫描取消
    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(endScanForPeriphers) object:nil];
    [self performSelector:@selector(endScanForPeriphers) withObject:nil afterDelay:timeout];
}

// 取消所有连接
- (void)cancelAllConnections {
    _isManualDisconnect = YES;
    for (CBPeripheral *peripheral in [_central retrieveConnectedPeripheralsWithServices:_serviceUUIDs]) {
        [_central cancelPeripheralConnection:peripheral];
    }
}

// 设备连接成功后，在发送数据前先发现服务
- (void)startDiscoverServiceForPeripheral:(CBPeripheral *)peripheral {
    BOOL canSendData = [self canSendDataForPeripheral:peripheral];
    peripheral.delegate = self;
    if (canSendData) {
        [self constructDataBridges:peripheral];
        return;
    }
    [peripheral discoverServices:_serviceUUIDs];
}

#pragma mark - Private Methods

// 能否向外设发送数据
- (BOOL)canSendDataForPeripheral:(CBPeripheral *)peripheral {
    BOOL isRxCharacterNotify = NO;
    BOOL isCtsCharacterNotify = NO;
    for (CBCharacteristic *character in [peripheral.services.firstObject characteristics]) {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        switch (uuidType) {
            case VBUUIDRxCharacteristic:
                isRxCharacterNotify = character.isNotifying;
                break;
            case VBUUIDCtsCharacteristic:
                isCtsCharacterNotify = character.isNotifying;
            default:
                break;
        }
    }
    
    // 只有在cts和rx通道都开启的情况下，才能发送数据
    BOOL canSendData = isRxCharacterNotify && isCtsCharacterNotify;
    return canSendData;
}

// 根据外设实例构造数据加工处理的桥接类
- (void)constructDataBridges:(CBPeripheral *)peripheral {
    CBService *primaryService = peripheral.services.firstObject;
    NSArray *characteristics = primaryService.characteristics;
    if (!characteristics) {
        return;
    }
    CBCharacteristic *txWriteCharacter;
    CBCharacteristic *rxReceiveCharacter;
    for (CBCharacteristic *character in characteristics) {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        if (uuidType == VBUUIDNone) {
            break;
        } else if (uuidType == VBUUIDTxCharacteristic) {
            txWriteCharacter = character;
        } else {
            if (uuidType == VBUUIDRxCharacteristic) {
                rxReceiveCharacter = character;
            }
            if (!character.isNotifying) {
                [peripheral setNotifyValue:YES forCharacteristic:character];
            }
        }
    }
    
    if (txWriteCharacter && rxReceiveCharacter) {
        NSUInteger index = [self peripheralIndexAtDataBridges:peripheral];
        // 移除旧的
        if (index != NSNotFound) {
            [_dataBridges removeObjectAtIndex:index];
        }
        VBDataBridge *bridge = [[VBDataBridge alloc] initWithPeripheral:peripheral writeCharacter:txWriteCharacter receiveCharacter:rxReceiveCharacter];
        bridge.delegate = self;
        [_dataBridges addObject:bridge];
    }
}

#pragma mark - CBCentralManager delegate

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {
    if (peripheral && ![_peripherals containsObject:peripheral] && [peripheral.name hasPrefix:@"硬件A的名称"]) {
        [_peripherals addObject:peripheral];
        
        for (id observer in _delegateObservers) {
            NSAssert([NSThread isMainThread], @"非主线程");
            if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
                [observer bluetoothManager:self didFindNewPeripheral:peripheral];
            }
        }
    }
}

#pragma mark - CBPeripheral delegate

// 1. 找到服务
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
    NSArray *services = peripheral.services;
    if (!services) {
        return;
    }
    
    for (CBService *service in services) {
        [peripheral discoverCharacteristics:_characterUUIDs forService:service];
    }
}

// 2. 找到特征
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
    [self constructDataBridges:peripheral];
}

...

@end

从以上未重构之前的VBBluetoothManager类的代码可以看到：该类确实耦合了大量跟特定外设信息相关的代码，导致现在新增加一种车载外设，却无法走通同样的通信流程。

解决方案

1. 抽取公共属性和方法

Untitled.gif

(1) ServiceUUIDs: 扫描外设时所用到的服务UUID数组；

(2) CharacterUUIDs: 读写数据特征和订阅特征的UUID数组；

(3) rxCharacterUUID: 嵌入式端告知的读数据的特征UUID，和txCharacterUUID一起用于构造数据加工处理类VBDataBridge实例，后者主要的作用是：收到数据处理的请求，交由VBDataBridge去决定是该接收类receiver去组装数据，还是sender类去拆包分次发送数据；

(4) txCharacterUUID: 嵌入式端告知的写数据的特征UUID，作用如上所述；

(5) peripheral: CBPeripheral实例类, 用该实例包装生成自己的蓝牙外设类，判断当前能否发送数据(canSendData)、开启订阅特征(notifyCharacter)等都需从该实例中执行相应操作；

(6) peripheralType: 外设类型，已知的外设类型枚举；

(7) prefixName: 外设的名称前缀；

(8) canSendData: 能否向外设发送数据，只有写数据通道处于notifying状态才可写；

(9) notifyCharacterForService:completionBlock::开启可读取或订阅特征的通道，并把对应的特征值通过block传回给调用方。

typedef void(^NotifyCharacterBlock)(CBCharacteristic *txWriteCharacter, CBCharacteristic *rxReceiveCharacter);

typedef NS_ENUM(NSInteger, VBPeripheralType) {
    VBPeripheralTypeUnknown,
    VBPeripheralTypeVbox,
    VBPeripheralTypeCarplay,
};

@protocol VBPeripheralProtocol 

+ (NSString *)prefixName;

@end

// interface
@interface VBPeripheral : NSObject

@property (nonatomic, assign, readonly) VBPeripheralType type;
@property (nonatomic, strong) CBPeripheral *peripheral;
@property (nonatomic, copy, readonly) NSArray *services;
@property (nonatomic, copy, readonly) NSArray *characterUUIDs;
@property (nonatomic, copy, readonly) CBUUID *rxCharacterUUID;
@property (nonatomic, copy, readonly) CBUUID *txCharacterUUID;

+ (instancetype)peripheralWithCBPeripheral:(CBPeripheral *)peripheral;
- (BOOL)canSendData;
- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion;

@end

// implementation
@implementation VBPeripheral

- (instancetype)initWithPeripheral:(CBPeripheral *)peripheral {
    
    self = [super init];
    if (self) {
        _peripheral = peripheral;
    }
    return self;
}

+ (instancetype)peripheralWithCBPeripheral:(CBPeripheral *)peripheral {
    if ([peripheral.name hasPrefix:[VBVboxPeripheral prefixName]]) {
        return [[VBVboxPeripheral alloc] initWithPeripheral:peripheral];
    } else if ([peripheral.name hasPrefix:[VBCarplayPeripheral prefixName]]) {
        return [[VBCarplayPeripheral alloc] initWithPeripheral:peripheral];
    } else {
        return nil;
    }
}

@end

2. 子类化对应外设模型

目前已知有两种蓝牙外设：硬件A和车载，每种设备有自己的服务和特征UUID，我们需要在具体的外设模型中实现上面抽象出来的属性和接口。

2.1 扩展VBUUIDType枚举类型

typedef NS_ENUM(NSInteger, VBUUIDType)
{
    VBUUIDNone = 0,
    // 车载设备的UUID
    VBCarplayServiceType = 0xFE00,
    VBCarplayTxCharacteristicType= 0xFE01,
    VBCarplayRxCharacteristicType = 0xFE02,
    // 硬件设备的UUID
    VBVboxServiceType = 0xFFF0,
    VBVboxTxCharacteristicType = 0xFFF1, // 手机向硬件发送LE数据的链路
    VBVboxRxCharacteristicType = 0xFFF2, // 手机从硬件接收LE数据的链路
    VBVboxCtsCharacteristicType = 0xFFF3, // 标识手机是否可以继续向硬件发送数据的链路,
};

2.2 硬件A外设模型

// interface
#import "VBPeripheralProtocol.h"
@interface VBVboxPeripheral :VBPeripheral

@end

// implementation
@implementation VBVboxPeripheral

- (VBPeripheralType)type {
    return VBPeripheralTypeVbox;
}

- (NSArray *)services {
    CBUUID *vboxService = [VBUUIDUtil UUIDWithType: VBVboxServiceType];
    return @[vboxService];
}

- (NSArray *)characterUUIDs {
    CBUUID *ctsCharacterUUID = [VBUUIDUtil UUIDWithType:VBVboxCtsCharacteristicType];
    return @[self.txCharacterUUID, self.rxCharacterUUID, ctsCharacterUUID];
}

- (CBUUID *)txCharacterUUID {
    return [VBUUIDUtil UUIDWithType:VBVboxTxCharacteristicType];
}

- (CBUUID *)rxCharacterUUID {
    return [VBUUIDUtil UUIDWithType:VBVboxRxCharacteristicType];
}

- (BOOL)canSendData {
    BOOL isRxCharacterNotify = NO;
    BOOL isCtsCharacterNotify = NO;
    for (CBCharacteristic *character in [self.peripheral.services.firstObject characteristics]) {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        switch (uuidType) {
            case VBVboxRxCharacteristicType:
                isRxCharacterNotify = character.isNotifying;
                break;
            case VBVboxCtsCharacteristicType:
                isCtsCharacterNotify = character.isNotifying;
            default:
                break;
        }
    }
    
    // 硬件设备只有在cts和rx都开启的情况下，才能发送数据
    BOOL canSendData = isRxCharacterNotify && isCtsCharacterNotify;
    return canSendData;
}

- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion {
    CBCharacteristic *txWriteCharacter;
    CBCharacteristic *rxReceiveCharacter;
    for (CBCharacteristic *character in service.characteristics)
    {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        switch (uuidType)
        {
            case VBVboxTxCharacteristicType:
                txWriteCharacter = character;
                break;
            case VBVboxRxCharacteristicType:
                rxReceiveCharacter = character;
                [self.peripheral setNotifyValue:YES forCharacteristic:character];
                break;
            case VBVboxCtsCharacteristicType:
                [self.peripheral setNotifyValue:YES forCharacteristic:character];
                break;
            default:
                break;
        }
    }
    
    completion(txWriteCharacter, rxReceiveCharacter);
}

+ (NSString *)prefixName {
    return @"硬件A的名称";
}

@end

2.3 车载外设模型

// interface
#import "VBPeripheralProtocol.h"

@interface VBCarplayPeripheral :VBPeripheral

@end

// implementation
@implementation VBCarplayPeripheral

- (VBPeripheralType)type {
    return VBPeripheralTypeCarplay;
}

- (NSArray *)services {
    CBUUID *carplayService = [VBUUIDUtil UUIDWithType:VBCarplayServiceType];
    return @[carplayService];
}

- (NSArray *)characterUUIDs {
    return @[self.txCharacterUUID, self.rxCharacterUUID];
}

- (CBUUID *)txCharacterUUID {
    return [VBUUIDUtil UUIDWithType:VBCarplayTxCharacteristicType];
}

- (CBUUID *)rxCharacterUUID {
    return [VBUUIDUtil UUIDWithType:VBCarplayRxCharacteristicType];
}

- (BOOL)canSendData {
    // 车载设备只要rx通道打开就能发送数据
    BOOL isRxNotifying = NO;
    for (CBCharacteristic *character in [self.peripheral.services.firstObject characteristics]) {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        if (uuidType == VBCarplayRxCharacteristicType) {
            isRxNotifying = character.isNotifying;
            break;
        }
    }
    
    return isRxNotifying;
}

- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion {
    CBCharacteristic *txWriteCharacter;
    CBCharacteristic *rxReceiveCharacter;
    for (CBCharacteristic *character in service.characteristics)
    {
        VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
        switch (uuidType)
        {
            case VBCarplayTxCharacteristicType:
                txWriteCharacter = character;
                break;
            case VBCarplayRxCharacteristicType:
                rxReceiveCharacter = character;
                [self.peripheral setNotifyValue:YES forCharacteristic:character];
                break;
            default:
                break;
        }
    }
    completion(txWriteCharacter, rxReceiveCharacter);
}

+ (NSString *)prefixName {
    return @"NeVSPS";
}

3. 重构VBBluetoothManager类

在VBBluetoothManager类的原有代码中，替换原先用到serviceUUIDs、characterUUIDs以及能否判断能否向外设发送代码的业务逻辑：

@interface VBBluetoothManager ()
{
    NSArray *_serviceUUIDs;
}
@end

@implementation VBBluetoothManager 

- (instancetype)init {
    self = [super init];
    if (self) {
    ...
        _serviceUUIDs = @[
                          [VBUUIDUtil UUIDWithType: VBVboxServiceType],
                          [VBUUIDUtil UUIDWithType: VBCarplayServiceType]];
    ...
    }
    return self;
}

- (void)startDiscoverServiceForPeripheral:(CBPeripheral *)peripheral {
    BOOL canSendData = [self canSendDataForPeripheral:peripheral];
    NELogVerbose(@"%s %@", __func__, @(canSendData));
    peripheral.delegate = self;
    id vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
    if ([vbPeripheral canSendData]) {
        return;
    }
    
    [peripheral discoverServices:vbPeripheral.services];
}

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {
    BOOL isVboxPeripheral = [peripheral.name hasPrefix:[VBVboxPeripheral prefixName]];
    BOOL isCarplayPeripheral = [peripheral.name hasPrefix:[VBCarplayPeripheral prefixName]];
    if (peripheral && ![_peripherals containsObject:peripheral] &&
        (isVboxPeripheral || isCarplayPeripheral)) {
        [_peripherals addObject:peripheral];
        
        for (id observer in _delegateObservers) {
            NSAssert([NSThread isMainThread], @"非主线程");
            if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
                [observer bluetoothManager:self didFindNewPeripheral:peripheral];
            }
        }
    }
}

#pragma mark - CBPeripheral delegate

// 1. 找到服务
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
    id vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
    for (CBService *service in peripheral.services) {
        [peripheral discoverCharacteristics:vbPeripheral.characterUUIDs forService:service];
    }
}

// 2. 找到特征
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
    id vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
    [vbPeripheral notifyCharactersForService:service completionBlock:^(CBCharacteristic *txWriteCharacter, CBCharacteristic *rxReceiveCharacter) {
        if (txWriteCharacter && rxReceiveCharacter) {
            NSUInteger index = [self peripheralIndexAtDataBridges:peripheral];
            // 移除旧的
            if (index != NSNotFound) {
                [_dataBridges removeObjectAtIndex:index];
            }
            VBDataBridge *bridge = [[VBDataBridge alloc] initWithPeripheral:peripheral writeCharacter:txWriteCharacter receiveCharacter:rxReceiveCharacter];
            bridge.delegate = self;
            [_dataBridges addObject:bridge];
        }
    }];
}

...
@end

至此，重构蓝牙管理类以支持多种设备的蓝牙数据通信工作就完成了，至于接收到数据之后，上层怎么处理又是另外一回事了，在此不谈。