在iOS中修改方法里面的BOOL

Question

我有一个UITableView显示图像的单元格.在cellForRowAtIndexPath方法上,我启动连接以获取图像.我想跟踪已经请求的图像,以避免多次请求相同的图像.

我设置了这样的方法

+(void) setImageFromURL:(NSURL*) url fromImage:(UIImage*) srcImage to:(UIImageView*) dstImage wasRequested:(BOOL*) requested;

并称之为这样

[Utils setImageFromURL:event.thumbURL fromImage:event.thumbImage to:cell.image wasRequested:event.thumbRequested];

event.thumbRequested是BOOL属性.方法看起来像这样

+(void) setImageFromURL:(NSURL*) url fromImage:(UIImage*) srcImage to:(UIImageView*) dstImage wasRequested:(BOOL*) requested{
    if (srcImage != nil) {
        dstImage.image = srcImage;
    } else if (!requested) {
        requested = YES;
        @try {
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                NSData * data = [[NSData alloc] initWithContentsOfURL: url];
                if ( data == nil )
                    return;
                dispatch_async(dispatch_get_main_queue(), ^{
                    __block UIImage* srcImage = [UIImage imageWithData: data];
                    dstImage.image = srcImage;
                });
                [data release];
            });
        }
        @catch (NSException *exception) {
            NSLog(exception.debugDescription);
        }
    }
}

我的问题是BOOL由于价值行为的传递而没有改变Objective-C.任何人都可以推荐一种能够BOOL从mehod内部更新事件对象的方法吗？

Answer 1

这条线:

requested = YES;

需要是:

if (requested) {
    *requested = YES;
}

检查只是nil因为传入了requested.

编辑:电话应该是:

BOOL requested = event.thumbRequested;
[Utils setImageFromURL:event.thumbURL fromImage:event.thumbImage to:cell.image wasRequested:&requested];
event.thumbRequested = requested;