iOS tableView中嵌套collectionView如何动态计算高度

tableview中嵌套collectionview的使用场景经常见，一般都是collectionview高度写死，那么如何在tableview高度自适应的情况下，collectionview的高度还能动态算准，可以通过以下方式,
在cell中重写-(CGSize)systemLayoutSizeFittingSize:(CGSize)targetSize withHorizontalFittingPriority:(UILayoutPriority)horizontalFittingPriority verticalFittingPriority:(UILayoutPriority)verticalFittingPriority方法

-(CGSize)systemLayoutSizeFittingSize:(CGSize)targetSize withHorizontalFittingPriority:(UILayoutPriority)horizontalFittingPriority verticalFittingPriority:(UILayoutPriority)verticalFittingPriority {
    CGSize size = [super systemLayoutSizeFittingSize:targetSize withHorizontalFittingPriority:horizontalFittingPriority verticalFittingPriority:verticalFittingPriority];
    [self.collectionView layoutIfNeeded]; 
    CGFloat height = self.collectionView.collectionViewLayout.collectionViewContentSize.height;;
    return CGSizeMake(size.width, height);
}

如果是tableview中嵌套tableview，需要动态计算高度的，可在cell中重写该方法：

-(CGSize)systemLayoutSizeFittingSize:(CGSize)targetSize withHorizontalFittingPriority:(UILayoutPriority)horizontalFittingPriority verticalFittingPriority:(UILayoutPriority)verticalFittingPriority{
    CGSize size = [super systemLayoutSizeFittingSize:targetSize withHorizontalFittingPriority:horizontalFittingPriority verticalFittingPriority:verticalFittingPriority];
    [self.tableView layoutIfNeeded];
    CGFloat heigth = self.tableView.contentSize.height;
    return CGSizeMake(size.width, heigth);
}