Centering a view in its superview using Visual Format Language

Question

I just started learning AutoLayout for iOS and had a look at Visual Format Language.

It all works fine except for one thing: I just can\'t get a view to center withi

Answer 1

I think it is better to manually create constraints.

[superview addConstraint:
 [NSLayoutConstraint constraintWithItem:view
                              attribute:NSLayoutAttributeCenterX
                              relatedBy:NSLayoutRelationEqual
                                 toItem:superview
                              attribute:NSLayoutAttributeCenterX
                             multiplier:1
                               constant:0]];
[superview addConstraint:
 [NSLayoutConstraint constraintWithItem:view
                              attribute:NSLayoutAttributeCenterY
                              relatedBy:NSLayoutRelationEqual
                                 toItem:superview
                              attribute:NSLayoutAttributeCenterY
                             multiplier:1
                               constant:0]];

---

Now we can use NSLayoutAnchor to programatically define AutoLayout:

(Available in iOS 9.0 and later)

view.centerXAnchor.constraint(equalTo: superview.centerXAnchor).isActive = true
view.centerYAnchor.constraint(equalTo: superview.centerYAnchor).isActive = true

---

I recommend using SnapKit, which is a DSL to make Auto Layout easy on both iOS and macOS.

view.snp.makeConstraints({ $0.center.equalToSuperview() })