我正在尝试使用 Apple 的一些源代码,但代码中充斥着以下语句:
require( error == nil, bail );
在 ARC 项目中使用时会导致各种错误(“转到受保护范围”)。
如何解决此代码?
这是一个例子:
- (void)setupAVCapture
{
NSError *error = nil;
AVCaptureSession *session = [AVCaptureSession new];
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone)
[session setSessionPreset:AVCaptureSessionPreset640x480];
else
[session setSessionPreset:AVCaptureSessionPresetPhoto];
// Select a video device, make an input
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
require( error == nil, bail ); //ERROR: "Goto into protected scope"
isUsingFrontFacingCamera = NO;
if ( [session canAddInput:deviceInput] )
[session addInput:deviceInput];
// Make a still image output
self.stillImageOutput = [AVCaptureStillImageOutput new];
[self.stillImageOutput addObserver:self forKeyPath:@"capturingStillImage" options:NSKeyValueObservingOptionNew context:(__bridge void *)(AVCaptureStillImageIsCapturingStillImageContext)];
if ( [session canAddOutput:self.stillImageOutput] )
[session addOutput:self.stillImageOutput];
// Make a video data output
self.videoDataOutput = [AVCaptureVideoDataOutput new];
// we want BGRA, both CoreGraphics and OpenGL work well with 'BGRA'
NSDictionary *rgbOutputSettings = [NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCMPixelFormat_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
[self.videoDataOutput setVideoSettings:rgbOutputSettings];
[self.videoDataOutput setAlwaysDiscardsLateVideoFrames:YES]; // discard if the data output queue is blocked (as we process the still image)
// create a serial dispatch queue used for the sample buffer delegate as well as when a still image is captured
// a serial dispatch queue must be used to guarantee that video frames will be delivered in order
// see the header doc for setSampleBufferDelegate:queue: for more information
videoDataOutputQueue = dispatch_queue_create("VideoDataOutputQueue", DISPATCH_QUEUE_SERIAL);
[self.videoDataOutput setSampleBufferDelegate:self queue:videoDataOutputQueue];
if ( [session canAddOutput:self.videoDataOutput] )
[session addOutput:self.videoDataOutput];
[[self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo] setEnabled:NO];
effectiveScale = 1.0;
self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
[self.previewLayer setBackgroundColor:[[UIColor blackColor] CGColor]];
[self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspect];
CALayer *rootLayer = [self.previewView layer];
[rootLayer setMasksToBounds:YES];
[self.previewLayer setFrame:[rootLayer bounds]];
[rootLayer addSublayer:self.previewLayer];
[session startRunning];
bail:
session = nil;
if (error) {
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:[NSString stringWithFormat:@"Failed with error %d", (int)[error code]]
message:[error localizedDescription]
delegate:nil
cancelButtonTitle:@"Dismiss"
otherButtonTitles:nil];
[alertView show];
[self teardownAVCapture];
}
}