iOS 正确的获取相册权限

获取相册权限,网上的写法,大多都感觉有点问题,不是特别完美. 

方案1: 直接给了返回值, 那对于PHAuthorizationStatusNotDetermined这种的,后面可能权限给了不允许, 然后还去调保存相册就会出问题.  这种方案不通过.

+ (BOOL)hasPermissionForPhotoGallery {
    PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
    if (status == PHAuthorizationStatusRestricted || status == PHAuthorizationStatusDenied) {
        return NO;
    }
    return YES;
}

方案2: 加了信号量,用信号量阻塞线程,当用户做了决定之后再返回.  看上去是没有问题的, 但是在使用的过程中发现了线程卡死.
第一次的时候 , 系统请求权限的弹框迟迟不出来,点击屏幕没有响应,之后推出一次后台,权限的弹窗才出现,同意/不同意 权限之后,才能解除死锁,不通过

+ (BOOL)isCanVisitPhotoLibrary {
    
    PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
    if (status == PHAuthorizationStatusAuthorized) {
        return YES;
    }
    if (status == PHAuthorizationStatusRestricted || status == PHAuthorizationStatusDenied) {
        return NO;
    }
    
    __block BOOL isAblity = YES;
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{
        [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
            if (status != PHAuthorizationStatusAuthorized) {
                NSLog(@"未开启相册权限,请到设置中开启");
                isAblity = NO;
                dispatch_semaphore_signal(semaphore);
            }
        }];
    });
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    return isAblity;
}

最终结果,由于PHAuthorizationStatusNotDetermined 这种的肯定是异步的给出结果,所以只能以异步对抗异步(用魔法打败魔法) , 所以结果只能在block中给出, 就变成了下面的这样,不会造成死锁,block中的结果肯定正确.
其他的相机,麦克风权限的获取也可以按照类似的方式

//MARK:相册权限检测
+ (void)isCanVisitPhotoLibrary:(void(^)(BOOL))result {
    
    /// 获取当前的状态
    //+ (PHAuthorizationStatus)authorizationStatus;
    /// 请求权限
    //+ (void)requestAuthorization:(void(^)(PHAuthorizationStatus status))handler;
    PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
    if (status == PHAuthorizationStatusAuthorized) {
        result(YES);
        return;
    }
    if (status == PHAuthorizationStatusRestricted || status == PHAuthorizationStatusDenied) {
        result(NO);
        return ;
    }
    
    if (status == PHAuthorizationStatusNotDetermined) {
        
        [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
            // 回调是在子线程的
            NSLog(@"%@",[NSThread currentThread]);
            dispatch_async(dispatch_get_main_queue(), ^{
                if (status != PHAuthorizationStatusAuthorized) {
                      NSLog(@"未开启相册权限,请到设置中开启");
                      result(NO);
                      return ;
                  }
                  result(YES);
            });
  
        }];
    }
    
}