在SDWebImageView庫中有一個名爲「SDWebImageDownloaderOperation」的類,它具有以下方法。爲什麼在SDWebImage中使用「willChangeValueForKey:」?
- (void)setFinished:(BOOL)finished {
[self willChangeValueForKey:@"isFinished"];
_finished = finished;
[self didChangeValueForKey:@"isFinished"];
}
然而,RS不覆蓋automaticallyNotifiesObserversForKey:
並沒有實現observeValueForKeyPath:ofObject:change:context:
方法,那麼什麼是寫在這裏
[self willChangeValueForKey:@"isFinished"]
和
[self didChangeValueForKey:@"isFinished"]