iOS Auto Layout Setting constraints programmatically
Example
Boilerplate code example
override func viewDidLoad() {
super.viewDidLoad()
let myView = UIView()
myView.backgroundColor = UIColor.blueColor()
myView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(myView)
// Add constraints code here
// ...
}
In the examples below the Anchor Style is the preferred method over NSLayoutConstraint Style, however it is only available from iOS 9, so if you are supporting iOS 8 then you should still use NSLayoutConstraint Style.
Pinning
Anchor Style
let margins = view.layoutMarginsGuide
myView.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor, constant: 20).active = true
- In addition to
leadingAnchor, there is alsotrailingAnchor,topAnchor, andbottomAnchor.
NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.Leading, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.LeadingMargin, multiplier: 1.0, constant: 20.0).active = true
- In addition to
.Leadingthere is also.Trailing,.Top, and.Bottom. - In addition to
.LeadingMarginthere is also.TrailingMargin,.TopMargin, and.BottomMargin.
Visual Format Language style
NSLayoutConstraint.constraintsWithVisualFormat("H:|-20-[myViewKey]", options: [], metrics: nil, views: ["myViewKey": myView])
Width and Height
Anchor Style
myView.widthAnchor.constraintEqualToAnchor(nil, constant: 200).active = true
myView.heightAnchor.constraintEqualToAnchor(nil, constant: 100).active = true
NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 200).active = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 100).active = true
Visual Format Language style
NSLayoutConstraint.constraintsWithVisualFormat("H:[myViewKey(200)]", options: [], metrics: nil, views: ["myViewKey": myView])
NSLayoutConstraint.constraintsWithVisualFormat("V:[myViewKey(100)]", options: [], metrics: nil, views: ["myViewKey": myView])
Center in container
Anchor Style
myView.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor).active = true
myView.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor).active = true
NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0).active = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0).active = true
Visual Format Language style
NSLayoutConstraint.constraintsWithVisualFormat("V:[viewKey]-(<=0)-[myViewKey]", options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: ["myViewKey": myView, "viewKey": view])
NSLayoutConstraint.constraintsWithVisualFormat("H:[viewKey]-(<=0)-[myViewKey]", options: NSLayoutFormatOptions.AlignAllCenterY, metrics: nil, views: ["myViewKey": myView, "viewKey": view])
