AnimatingConstraints1.swift

linesConvergingAnimation = UIViewPropertyAnimator(duration: 0.2, curve: UIViewAnimationCurve.linear, animations: {
    // Set the new constraints
    self.firstLine.snp.remakeConstraints({ (make) in
        make.height.equalTo(self.lineHeight) // constant
        make.width.equalTo(self.containerView.snp.width)
        make.centerX.equalTo(self.containerView.snp.centerX)
        make.centerY.equalTo(self.containerView.snp.centerY)
    })
    self.thirdLine.snp.remakeConstraints({ (make) in
        make.height.equalTo(self.lineHeight) // constant
        make.width.equalTo(self.containerView.snp.width)
        make.centerX.equalTo(self.containerView.snp.centerX)
        make.centerY.equalTo(self.containerView.snp.centerY)
    })
    // Apply the new constraints on the view
    self.view.layoutIfNeeded()
})