使用代码而非情节提要添加的View自动布局（VFL）

Question

If I add views from storyboard I can handle their autolayout contraints via code, but if I try this on a view that is added via code, can't handle it.

I'm calling the code below in my viewDidLoad() but doesn't works, what is the missing part?

    var testView = UIView()
    testView.backgroundColor = UIColor.greenColor()
    self.view.addSubview(testView)

    let views : [String : AnyObject] = ["testView": testView]
    var allConstraints = [NSLayoutConstraint]()

    let verticalConstraint = NSLayoutConstraint.constraintsWithVisualFormat(
        "V:|-[testView(100)]",
        options: [],
        metrics: nil,
        views: views)
    allConstraints += verticalConstraint

    let horizontalConstraint = NSLayoutConstraint.constraintsWithVisualFormat(
        "H:|-[testView(200)]",
        options: [],
        metrics: nil,
        views: views)
    allConstraints += horizontalConstraint

    NSLayoutConstraint.activateConstraints(allConstraints)

ps: also tried these lines but didn't help

    self.view.addConstraints(verticalConstraint)
    self.view.addConstraints(horizontalConstraint)

Answer 1

You need to turn off translation of autoresizing masks to constraints. By default its set to true and if you tend to forget this, it will add constraints which you did not intend to.

You can set this to false by

var myView = UIView()
myView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(myView)

translatesAutoresizingMaskIntoConstraints

If this property's value is YES, the system creates a set of constraints that duplicate the behavior specified by the view's autoresizing mask. By default, the property is set to YES for any view you programmatically create. If you add views in Interface Builder, the system automatically sets this property to NO.