iOS KVO取值

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
    if ([keyPath isEqualToString:kContentSizeKey])
    {
        CGSize contentSize;
        id newValue = [change valueForKey:NSKeyValueChangeNewKey];
        [(NSValue*)newValue getValue:&contentSize];
        self.tableView.height = contentSize.height;
        [self.collectionView reloadData];
    YDLog(@"🤣contentSize=%@,string=%@",newValue, NSStringFromCGSize(contentSize));
    }
    else
    {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

输出：

🤣contentSize=NSSize: {414, 1002.57678125},string={414, 1002.57678125}

注意：newValue并不等于NSStringFromCGSize(contentSize)，所以不能用key直接取值，因为它存的不是一个字符串，而是一个NSSize结构体