objective-c - Objective-C 中的 block 变量

Question

我对 Objective-C 中的 block 有疑问。

例如我有这个代码:

__block int count = 0;
void (^someFunction)(void) = ^(void){
count = 4;
};
count +=2;

编写同一段代码以使计数变为 6 而不是 2 的正确方法是什么？!

谢谢!

我可能应该显示实际的代码，因为我之前的问题很模糊。编辑:

__block CMTime lastTime = CMTimeMake(-1, 1);
    __block int count = 0;
    [_imageGenerator generateCGImagesAsynchronouslyForTimes:stops
                                          completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime,
                                                              AVAssetImageGeneratorResult result, NSError *error)
     {
         if (result == AVAssetImageGeneratorSucceeded)
         {
             NSImage *myImage = [[NSImage alloc] initWithCGImage:image size:(NSSize){50.0,50.0}];
             [arrOfImages addObject:myImage];
         }

         if (result == AVAssetImageGeneratorFailed)
         {
             NSLog(@"Failed with error: %@", [error localizedDescription]);
         }
         if (result == AVAssetImageGeneratorCancelled)
         {
             NSLog(@"Canceled");
         }
         if (arrOfImages.count > 5)
         {
             NSLog(@"here");
         }
         count++;
     }];
     int f = count+1;

10次迭代后计数为0...为什么？!？!

Answer 1

您没有执行该 block (调用 block someFunction 可能会产生误导)

__block int count = 0;
void (^someBlock)(void) = ^{
    count = 4;
};
someBlock();
count +=2;