Width constraint change with UIView animation

Question

I have width constraint which I update through SnapKit. Expanding animation:

self.snp.updateConstraints({(make) in
    make.width.equalTo(150.0)
})

Collapsing animation:

self.snp.updateConstraints({(make) in
    make.width.equalTo(150.0)
})

When I animate this through:

UIView.animate(withDuration: 0.5,animations: {
    self.layoutIfNeeded()
}, completion: nil)

My view change width by expanding first jumping to left, and then expanding from left to right because my "animated" view trailing anchor equal to superview trailing anchor.

slider.snp.makeConstraints({(make) in
    make.trailing.equalToSuperview()
    make.centerY.equalToSuperview()
    make.height.equalTo(slider.getContentHeight())
    make.width.equalTo(slider.labels.first?.intrinsicContentSize.width ?? 30.0)
})

So i would like to animation be expanding from right to left

Answer 1

I achieved desired result by changing view.center.x . I tried to change leading constraint and width but it didn't work out. I also happen to change width of my view but it happens without animation and before/after for expand/collapse respectively. So here is my code:

self.snp.updateConstraints({(make) in
    make.width.equalTo(150.0)
})

UIView.animate(withDuration: 0.2,
    animations: {
        self.center.x -= 90
        self.layoutIfNeeded()
    }, completion: nil)

And reverse :

UIView.animate(withDuration: 0.2,
    animations: {
        self.center.x += 90
        self.layoutIfNeeded()
    }, completion: nil)

self.snp.updateConstraints({(make) in
    make.width.equalTo(30.0)
})

Animation is a bit rough when it comes to collapsing but works just fine for expanding. Still appreciate any suggestion.