How to add a subview with constraints to make the subview with the same frame as its superview?

Question

Within UIView I have a method presentView():

public func presentView() {

    UIApplication.sharedApplication().delegate?.window??.addSubview(self)

    let blurEffect = UIBlurEffect(style: .Light)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.backgroundColor = UIColor.yellowColor()
    addSubview(blurEffectView)

    let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
    let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
    let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Leading, multiplier: 1, constant: 0)
    let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Trailing, multiplier: 1, constant: 0)

    self.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])

    print("newframe: \(blurEffectView.frame)")

}

but sth is wrong because this is the output on console:

newframe: (0.0, 0.0, 0.0, 0.0)

and result is:

If I'm reading correctly, `self` is a `UIView`. Then you should add the constraints to `self` rather then `blurEffectView`. — Dániel Nagy, Sep 28 '15 at 12:11
@DánielNagy I updated the question, can you help me to solve this out? — Bartłomiej Semańczyk, Sep 28 '15 at 12:35
I think until the view is not layed out, you won't get it's actual frame. So after `self.addConstraints` you won't get it right now. — Dániel Nagy, Sep 28 '15 at 13:00
Again updated the question with new info. I set background color to yellow, but there is no my view at all. — Bartłomiej Semańczyk, Sep 28 '15 at 13:04
[This SO question](https://stackoverflow.com/questions/26180822/swift-adding-constraints-programmatically) has a lot of good information on programmatically adding constraints. — Derek Soike, Mar 09 '18 at 20:39

score 13 · Answer 1 · edited Nov 16 '18 at 05:49

Remember about:

blurEffectView.translatesAutoresizingMaskIntoConstraints = false

and then:

let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: .Leading, multiplier: 1, constant: 0)
let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: .Trailing, multiplier: 1, constant: 0)

addSubview(blurEffectView)
addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])
layoutIfNeeded()

How to add a subview with constraints to make the subview with the same frame as its superview?

1 Answers1