2019-08-02 snapkit动画失效的问题

weak var weakself = self
UIView.animate(withDuration: 0.5) {
                weakself?.titleView?.snp.updateConstraints({ (make) in
                    make.top.equalTo((weakself?.topView.snp.bottom)!)
                })
                weakself?.view.layoutIfNeeded()//立即刷新view
            }