Using Autolayout Visual Format with Swift?

Question

I\'ve been trying to use the Autolayout Visual Format Language in Swift, using NSLayoutConstraint.constraintsWithVisualFormat. Here\'s an example of some code that

Answer 1

This works with Xcode 6.1.1:

extension NSView {

    func addConstraints(constraintsVFL: String, views: [String: NSView], metrics: [NSObject: AnyObject]? = nil, options: NSLayoutFormatOptions = NSLayoutFormatOptions.allZeros) {
        let mutableDict = (views as NSDictionary).mutableCopy() as NSMutableDictionary
        let constraints = NSLayoutConstraint.constraintsWithVisualFormat(constraintsVFL, options: options, metrics: metrics, views: mutableDict)
        self.addConstraints(constraints)
    }

}

Then you can use calls like:

var views : [String: NSView] = ["box": self.box]
self.view.addConstraints("V:[box(100)]", views: views)

This works to add constraints. If you are using iOS, substitute UIView for NSView

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You should probably check out

• Cartography, which is a new approach, but quite awesome. It uses Autolayout under the hood.
• SnapKit, which I haven't tried but is also a DSL autolayout framework

Answer 2

this works for me with no error:

let bar:[AnyObject]! = NSLayoutConstraint.constraintsWithVisualFormat(
  nil, options: NSLayoutFormatOptions(0), metrics: nil, views: nil)

update

the line above may not be compiled since the 1^st and 4^th parameters cannot be optionals anymore.

syntactically those have to be set, like e.g. this:

let bar:[AnyObject] = NSLayoutConstraint.constraintsWithVisualFormat("", options: NSLayoutFormatOptions(0), metrics: nil, views: ["": self.view])

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update

(for Xcode 7, Swift 2.0)

the valid syntax now requests the parameters's name as well, like:

NSLayoutFormatOptions(rawValue: 0)

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NOTE: this line of code shows the correct syntax only, the parameters itself won't guarantee the constraint will be correct or even valid!

Answer 3

Try this - remove the initial variable name (format:), use NSLayoutFormatOptions(0), and just pass nil for those optional NSDictionaries:

let foo:[AnyObject]! = NSLayoutConstraint.constraintsWithVisualFormat("", options: NSLayoutFormatOptions(0), metrics: nil, views: nil)