iOS view visibility gone

Question

I am new to iOS development.I want to toggle (hide/visible) a subview from parent view.In android there is a way to hide the visibility to gone.

In android

subView.setVisibility(View.GONE);

In iOS

subView.removeFromSuperview()

when i use above function it remove subViewConstraints and mess up my scroll view constraints.

topsubView.bottomAnchor.constraint(equalTo: bottomSubView.topAnchor, constant: 8).isActive = true

when i use the above code it works fine and hide subView.but when i want to make subView visible,it is not showing the subView.

topsubView.bottomAnchor.constraint(equalTo: bottomSubView.topAnchor, constant: 8).isActive = false
self.view.layoutIfNeeded()

Hope you understand my problem.Thanks in Advance.

Answer 1

As I have worked on both iOS & Android, You need to play with constraint outlet in ios to achieve Android functioning. iOS Does not support automatically like Android native support on visibility GONE & VISIBLE

You need to hook the outlet of particular constraint(it may vertical/horizontal/height) you need to set it to 0 & need to manage your UI.

To Hide:

self.viewYourConstraint.constant = 0
self.yourView.hidden = true
self.view.layoutIfNeeded()

To Show:

self.viewYourConstraint.constant = 100//your constant value
self.yourView.hidden = false
self.view.layoutIfNeeded()

Note: If other constraints will be affected because of the update to the constraint above, the following must also need to be called:

self.yourView.setNeedsUpdateConstraints()

Answer 2

Try this extension:

extension UIView {
    
    func visiblity(gone: Bool, dimension: CGFloat = 0.0, attribute: NSLayoutAttribute = .height) -> Void {
        if let constraint = (self.constraints.filter{$0.firstAttribute == attribute}.first) {
            constraint.constant = gone ? 0.0 : dimension
            self.layoutIfNeeded()
            self.isHidden = gone
        }
    }
}

How you can use this....

@IBOutlet weak var testView: UIView?
@IBAction func testVisibilty(switchbutton: UISwitch) -> Void {
    
    let viewHeight:CGFloat = switchbutton.isOn ? 100 : 0.0
    self.testView?.visiblity(gone: !switchbutton.isOn, dimension: viewHeight)
    
    // set visibility for width constraint
    //let viewWidth:CGFloat = switchbutton.isOn ? 300 : 0.0
    //self.testView?.visiblity(gone: !switchbutton.isOn, dimension: viewWidth, attribute: .width)
  
}

Here is result:

Answer 3

Maybe you'd prefer this solution

extension UIView {

    enum Visibility {
        case visible
        case invisible
        case gone
    }

    var visibility: Visibility {
        get {
            let constraint = (self.constraints.filter{$0.firstAttribute == .height && $0.constant == 0}.first)
            if let constraint = constraint, constraint.isActive {
                return .gone
            } else {
                return self.isHidden ? .invisible : .visible
            }
        }
        set {
            if self.visibility != newValue {
                self.setVisibility(newValue)
            }
        }
    }

    private func setVisibility(_ visibility: Visibility) {
        let constraint = (self.constraints.filter{$0.firstAttribute == .height && $0.constant == 0}.first)

        switch visibility {
        case .visible:
            constraint?.isActive = false
            self.isHidden = false
            break
        case .invisible:
            constraint?.isActive = false
            self.isHidden = true
            break
        case .gone:
            if let constraint = constraint {
                constraint.isActive = true
            } else {
                let constraint = NSLayoutConstraint(item: self, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .height, multiplier: 1, constant: 0)
                self.addConstraint(constraint)
                constraint.isActive = true
            }
        }
    }
}

then the usage is:

someView.visibility = .visible
someView.visibility = .invisible
someView.visibility = .gone

edit:

improving capabilities: will work from storyboard (just write: 'visible', 'invisible', 'gone') in the "Visibility State"

all constraints inside view should be less then a 1000

extension UIView {

    enum Visibility: String {
        case visible = "visible"
        case invisible = "invisible"
        case gone = "gone"
    }

    var visibility: Visibility {
        get {
            let constraint = (self.constraints.filter{$0.firstAttribute == .height && $0.constant == 0}.first)
            if let constraint = constraint, constraint.isActive {
                return .gone
            } else {
                return self.isHidden ? .invisible : .visible
            }
        }
        set {
            if self.visibility != newValue {
                self.setVisibility(newValue)
            }
        }
    }

    @IBInspectable
    var visibilityState: String {
        get {
            return self.visibility.rawValue
        }
        set {
            let _visibility = Visibility(rawValue: newValue)!
            self.visibility = _visibility
        }
    }

    private func setVisibility(_ visibility: Visibility) {
        let constraints = self.constraints.filter({$0.firstAttribute == .height && $0.constant == 0 && $0.secondItem == nil && ($0.firstItem as? UIView) == self})
        let constraint = (constraints.first)

        switch visibility {
        case .visible:
            constraint?.isActive = false
            self.isHidden = false
            break
        case .invisible:
            constraint?.isActive = false
            self.isHidden = true
            break
        case .gone:
            self.isHidden = true
            if let constraint = constraint {
                constraint.isActive = true
            } else {
                let constraint = NSLayoutConstraint(item: self, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .height, multiplier: 1, constant: 0)
                // constraint.priority = UILayoutPriority(rawValue: 999)
                self.addConstraint(constraint)
                constraint.isActive = true
            }
            self.setNeedsLayout()
            self.setNeedsUpdateConstraints()
        }
    }
}