在dispatch_async那里报错了：Cannot jump from switch statement to this case label

Question

-(void)centralManagerDidUpdateState:(CBCentralManager *)central{
    switch (central.state) {
        case CBPeripheralManagerStatePoweredOn:
            NSLog(@"BLE已打开.");
            [self writeToLog:@"BLE已打开."];
            //扫描外围设备
            
            dispatch_async(dispatch_get_main_queue(), ^{
                [central scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey:@YES}];
            });
            break;
            
        default:
            NSLog(@"此设备不支持BLE或未打开蓝牙功能，无法作为外围设备.");
            [self writeToLog:@"此设备不支持BLE或未打开蓝牙功能，无法作为外围设备."];
            break;
    }
}希望能得到错误的具体原因？

Answer 1

还未编译程序，在default哪里报错：Cannot jump from switch statement to this case label。希望能得到错误的具体原因？

Answer 2

http://stackoverflow.com/questions/33550588/defining-a-block-in-a-switch-statement-results-in-a-compiler-error

Answer 3

呵呵，应该是作用域的问题，如果在case 的判断中是一些语句体，需要用 花括号 {} 括起来-(void)centralManagerDidUpdateState:(CBCentralManager *)central{
    switch (central.state) {
        case CBPeripheralManagerStatePoweredOn: {
            NSLog(@"BLE已打开.");
            [self writeToLog:@"BLE已打开."];
            //扫描外围设备
             [central scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey:@YES}];
            break;
         }
        default: {
            NSLog(@"此设备不支持BLE或未打开蓝牙功能，无法作为外围设备.");
            [self writeToLog:@"此设备不支持BLE或未打开蓝牙功能，无法作为外围设备."];
           }
            break;
    }
}