cell高度自适应

- (CGFloat)cellHeight {
    NSLayoutConstraint *tempWidthConstraint =
    [NSLayoutConstraint constraintWithItem:self.contentView
                                 attribute:NSLayoutAttributeWidth
                                 relatedBy:NSLayoutRelationEqual
                                    toItem:nil
                                 attribute:NSLayoutAttributeNotAnAttribute
                                multiplier:1.0
                                  constant:CGRectGetWidth(self.frame)];
    
    [self.contentView addConstraint:tempWidthConstraint];
    
    // Auto layout engine does its math
    CGSize fittingSize = [self.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
    
    [self.contentView removeConstraint:tempWidthConstraint];
    
    return fittingSize.height+5;
}

注意：

一、变更的label高度不能写死，固定上下左右

二、在自定义cell的位置要传model，根据model中的数据计算高度