Adding constraints in awakeFromNib() method

Question

I have two custom views in my project which needs to be zoomed in the exact same proportion. So I decided to use UIScrollView for that and it fits perfectly.

I decided to develop a very simple class inherited from UIScrollView and inside of it I initialized all views structure. That way I'm avoiding any construction steps in the NIB file and my class can be used just by adding one view. But I faced an issue already on the stage of adding contentView.

Here's my class:

final class PlayerContentView: UIScrollView {
    fileprivate var contentView: UIView!

    override func awakeFromNib() {
        super.awakeFromNib()

        self.backgroundColor = .clear
        setupScrollProperties()

        setupContentView()
    }

    private func setupScrollProperties()
    {
        self.translatesAutoresizingMaskIntoConstraints = false
        self.minimumZoomScale = 1.0
        self.maximumZoomScale = 2.0
        self.contentSize = frame.size
        self.delegate = self
    }

    private func setupContentView()
    {
        contentView = UIView(frame: self.frame)
        contentView.backgroundColor = .red
        self.addSubview(contentView)

        CommonSwiftUtility.setSideConstraints(superview: self, view: contentView)
        CommonSwiftUtility.setSizeConstraints(superview: self, view: contentView)
    }


    func requireToFail(_ gestureRecognizer: UIPanGestureRecognizer) {
        self.panGestureRecognizer.require(toFail: gestureRecognizer)
    } }

And here're methods for adding constraints:

static func setSideConstraints(superview: UIView, view: UIView) {
        let topConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                   attribute: .top,
                                                                   relatedBy: .equal,
                                                                   toItem: superview,
                                                                   attribute: .top,
                                                                   multiplier: 1.0, constant: 0.0)

        let bottomConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                      attribute: .bottom,
                                                                      relatedBy: .equal,
                                                                      toItem: superview,
                                                                      attribute: .bottom,
                                                                      multiplier: 1.0, constant: 0.0)

        let leadingConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                       attribute: .leading,
                                                                       relatedBy: .equal,
                                                                       toItem: superview,
                                                                       attribute: .leading,
                                                                       multiplier: 1.0, constant: 0.0)

        let trailingConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                        attribute: .trailing,
                                                                        relatedBy: .equal,
                                                                        toItem: superview,
                                                                        attribute: .trailing,
                                                                        multiplier: 1.0, constant: 0.0)

        superview.addConstraint(topConstraint)
        superview.addConstraint(bottomConstraint)
        superview.addConstraint(leadingConstraint)
        superview.addConstraint(trailingConstraint)
    }

    static func setSizeConstraints(superview: UIView, view: UIView)
    {
        let wConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                 attribute: .width,
                                                                 relatedBy: .equal,
                                                                 toItem: superview,
                                                                 attribute: .width,
                                                                 multiplier: 1.0, constant: 0.0)

        let hConstraint: NSLayoutConstraint = NSLayoutConstraint(item: view,
                                                                 attribute: .height,
                                                                 relatedBy: .equal,
                                                                 toItem: superview,
                                                                 attribute: .height,
                                                                 multiplier: 1.0, constant: 0.0)

        superview.addConstraint(wConstraint)
        superview.addConstraint(hConstraint)
    }

As you can see, I painted my contentView in red color in order to define it on the screen. After showing my PlayerContentView I get this:

PlayerContentView is stretched on the full screen so I'm expecting contentView to be full-size, but clearly it's not. Could someone please refer me to the solution of that issue? Thanks in advance!

Shehata Gamal · Accepted Answer · 2019-04-01 13:13:25Z

1

Can you set

contentView.translatesAutoresizingMaskIntoConstraints = false

answered Apr 1, 2019 at 13:13

Shehata Gamal

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4 Comments

Eugene Alexeev Over a year ago

Hello and thank you for your response! As you can see in setupScrollProperties() method, I did it, but it didn't change anything :(

Shehata Gamal Over a year ago

you set it for self not contentView

Eugene Alexeev Over a year ago

You are 100% correct, sir! Your solution did help, thank you very much! But one note: I need to set every single subview translatesAutoresizingMaskIntoConstraints to false in order to apply constraints.

Tushar Katyal Over a year ago

Yes, you've to update this property to false in order to set constraints

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