某硬件項目藍牙管理類VBBluetoothManager重構

[toc]

業(yè)務背景

正如上篇iOS端智能硬件BLE通信技術實現(xiàn)一文所述，整個藍牙庫的最初設計實現(xiàn)最初都是為硬件通信服務的，19年年前突然接到需求，希望通過車載上放置的藍牙收音設備，讓用戶在喚醒設備后，直接將用戶的語音指令轉成app里面可執(zhí)行的操作，如“XXX, 播放每日XX的歌”，“XXX，上/下一首”等一些當前app用戶常用的操作，產品希望通過這類車載設備來擴大app現(xiàn)有用戶的使用場景甚至探尋增加新用戶的可能。

現(xiàn)有問題

其實原app中藍牙通信目前已經有兩套代碼了，一套用于早先的藍牙耳機，一套用于硬件A業(yè)務，硬件A業(yè)務由于是18年11月才并入現(xiàn)有app的，存在兩套代碼也無可厚非，現(xiàn)在又增加了新的車載設備，難道再編寫一套為車載設備而設計的藍牙通信方案嗎？作為一個有節(jié)操的程序媛，當然不可能這么做了?。?br> 首先跟嵌入式端同學約定：車載設備的通信協(xié)議復用原有硬件A的那一套，這樣數(shù)據(jù)收發(fā)處理（發(fā)送拆包接收組包）的代碼就能復用，但是負責管理藍牙一系列通信行為（掃描、停止掃描、連接、發(fā)現(xiàn)服務、斷開連接、接收藍牙數(shù)據(jù)等）以及提供發(fā)送數(shù)據(jù)接口和回調收到的數(shù)據(jù)給用戶的VBBluetoothManager類, 耦合了掃描硬件A的標識符serviceUUID, 讀寫硬件A特征值的標識符characteristicUUID, 甚至有在已掃描到的設備列表中根據(jù)硬件名稱或UUID查找特定設備的接口，其中的很多接口都是為硬件A通信服務的，先看下原有部分代碼：

// from VBBluetoothManager.m, 以下...表示省略其他無關代碼
@interface VBBluetoothManager ()<VBDataBridgeDelegate,CBCentralManagerDelegate,CBPeripheralDelegate>
{
    ...
    NSArray *_serviceUUIDs;
    NSMutableArray *_characterUUIDs;
    ...
}

@implementation VBBluetoothManager

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

#pragma mark - Public Methods

// 掃描外設
- (void)scanWithDurationWithTimeout:(NSTimeInterval)timeout resetPrevScan:(BOOL)isReset {
    if (isReset) {
        [self resetScan];
    }
    // 前臺時不指定serviceUUID去掃描（兼容嵌入式舊版本，舊版本藍牙名稱很長，超過了藍牙廣播包的長度限制，導致根據(jù)serviceUUID無法掃描到）
    // 后臺的話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}];
    // 先將之前的掃描取消
    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(endScanForPeriphers) object:nil];
    [self performSelector:@selector(endScanForPeriphers) withObject:nil afterDelay:timeout];
}

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

// 設備連接成功后，在發(fā)送數(shù)據(jù)前先發(fā)現(xiàn)服務
- (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

// 能否向外設發(fā)送數(shù)據(jù)
- (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通道都開啟的情況下，才能發(fā)送數(shù)據(jù)
    BOOL canSendData = isRxCharacterNotify && isCtsCharacterNotify;
    return canSendData;
}

// 根據(jù)外設實例構造數(shù)據(jù)加工處理的橋接類
- (void)constructDataBridges:(CBPeripheral *)peripheral {
    CBService *primaryService = peripheral.services.firstObject;
    NSArray<CBCharacteristic *> *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];
        // 移除舊的
        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<NSString *,id> *)advertisementData RSSI:(NSNumber *)RSSI {
    if (peripheral && ![_peripherals containsObject:peripheral] && [peripheral.name hasPrefix:@"硬件A的名稱"]) {
        [_peripherals addObject:peripheral];
        
        for (id<VBBluetoothManagerDelegate> observer in _delegateObservers) {
            NSAssert([NSThread isMainThread], @"非主線程");
            if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
                [observer bluetoothManager:self didFindNewPeripheral:peripheral];
            }
        }
    }
}

#pragma mark - CBPeripheral delegate

// 1. 找到服務
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
    NSArray<CBService *> *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

從以上未重構之前的VBBluetoothManager類的代碼可以看到：該類確實耦合了大量跟特定外設信息相關的代碼，導致現(xiàn)在新增加一種車載外設，卻無法走通同樣的通信流程。

解決方案

1. 抽取公共屬性和方法

Untitled.gif

(1) ServiceUUIDs: 掃描外設時所用到的服務UUID數(shù)組；

(2) CharacterUUIDs: 讀寫數(shù)據(jù)特征和訂閱特征的UUID數(shù)組；

(3) rxCharacterUUID: 嵌入式端告知的讀數(shù)據(jù)的特征UUID，和txCharacterUUID一起用于構造數(shù)據(jù)加工處理類VBDataBridge實例，后者主要的作用是：收到數(shù)據(jù)處理的請求，交由VBDataBridge去決定是該接收類receiver去組裝數(shù)據(jù)，還是sender類去拆包分次發(fā)送數(shù)據(jù)；

(4) txCharacterUUID: 嵌入式端告知的寫數(shù)據(jù)的特征UUID，作用如上所述；

(5) peripheral: CBPeripheral實例類, 用該實例包裝生成自己的藍牙外設類，判斷當前能否發(fā)送數(shù)據(jù)(canSendData)、開啟訂閱特征(notifyCharacter)等都需從該實例中執(zhí)行相應操作；

(6) peripheralType: 外設類型，已知的外設類型枚舉；

(7) prefixName: 外設的名稱前綴；

(8) canSendData: 能否向外設發(fā)送數(shù)據(jù)，只有寫數(shù)據(jù)通道處于notifying狀態(tài)才可寫；

(9) notifyCharacterForService:completionBlock::開啟可讀取或訂閱特征的通道，并把對應的特征值通過block傳回給調用方。

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

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

@protocol VBPeripheralProtocol <NSObject>

+ (NSString *)prefixName;

@end

// interface
@interface VBPeripheral : NSObject

@property (nonatomic, assign, readonly) VBPeripheralType type;
@property (nonatomic, strong) CBPeripheral *peripheral;
@property (nonatomic, copy, readonly) NSArray<CBUUID *> *services;
@property (nonatomic, copy, readonly) NSArray<CBUUID *> *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. 子類化對應外設模型

目前已知有兩種藍牙外設：硬件A和車載，每種設備有自己的服務和特征UUID，我們需要在具體的外設模型中實現(xiàn)上面抽象出來的屬性和接口。

2.1 擴展VBUUIDType枚舉類型
typedef NS_ENUM(NSInteger, VBUUIDType)
{
    VBUUIDNone = 0,
    // 車載設備的UUID
    VBCarplayServiceType = 0xFE00,
    VBCarplayTxCharacteristicType= 0xFE01,
    VBCarplayRxCharacteristicType = 0xFE02,
    // 硬件設備的UUID
    VBVboxServiceType = 0xFFF0,
    VBVboxTxCharacteristicType = 0xFFF1, // 手機向硬件發(fā)送LE數(shù)據(jù)的鏈路
    VBVboxRxCharacteristicType = 0xFFF2, // 手機從硬件接收LE數(shù)據(jù)的鏈路
    VBVboxCtsCharacteristicType = 0xFFF3, // 標識手機是否可以繼續(xù)向硬件發(fā)送數(shù)據(jù)的鏈路,
};
2.2 硬件A外設模型
// interface
#import "VBPeripheralProtocol.h"
@interface VBVboxPeripheral :VBPeripheral

@end

// implementation
@implementation VBVboxPeripheral

- (VBPeripheralType)type {
    return VBPeripheralTypeVbox;
}

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

- (NSArray<CBUUID *> *)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;
        }
    }
    
    // 硬件設備只有在cts和rx都開啟的情況下，才能發(fā)送數(shù)據(jù)
    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的名稱";
}

@end
2.3 車載外設模型
// interface
#import "VBPeripheralProtocol.h"

@interface VBCarplayPeripheral :VBPeripheral

@end

// implementation
@implementation VBCarplayPeripheral

- (VBPeripheralType)type {
    return VBPeripheralTypeCarplay;
}

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

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

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

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

- (BOOL)canSendData {
    // 車載設備只要rx通道打開就能發(fā)送數(shù)據(jù)
    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. 重構VBBluetoothManager類

在VBBluetoothManager類的原有代碼中，替換原先用到serviceUUIDs、characterUUIDs以及能否判斷能否向外設發(fā)送代碼的業(yè)務邏輯：

@interface VBBluetoothManager ()
{
    NSArray<CBUUID *> *_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<VBPeripheralProtocol> vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
    if ([vbPeripheral canSendData]) {
        return;
    }
    
    [peripheral discoverServices:vbPeripheral.services];
}

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *,id> *)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<VBBluetoothManagerDelegate> observer in _delegateObservers) {
            NSAssert([NSThread isMainThread], @"非主線程");
            if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
                [observer bluetoothManager:self didFindNewPeripheral:peripheral];
            }
        }
    }
}

#pragma mark - CBPeripheral delegate

// 1. 找到服務
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
    id<VBPeripheralProtocol> 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<VBPeripheralProtocol> vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
    [vbPeripheral notifyCharactersForService:service completionBlock:^(CBCharacteristic *txWriteCharacter, CBCharacteristic *rxReceiveCharacter) {
        if (txWriteCharacter && rxReceiveCharacter) {
            NSUInteger index = [self peripheralIndexAtDataBridges:peripheral];
            // 移除舊的
            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，重構藍牙管理類以支持多種設備的藍牙數(shù)據(jù)通信工作就完成了，至于接收到數(shù)據(jù)之后，上層怎么處理又是另外一回事了，在此不談。

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