Change Swift constraint on if statement - ios

Question

Here is my tableview row/cell:
there are constraints set in place - the imageview is below the label and the button is below the imageview.
here is my code:
if(row == 1) {
imageview.hidden = false
} else {
imageview.hidden = true
//how can i change the button constraint from below imageview to below label?

Answer 1

Adding and removing constraints is really bad example for that. I'll make your UI more complex.
Best way of solving these auto-layout problems is adding two constraints. One from imageView to button and second from imageView to label.
Now after setting these constraints, you need to set their priority levels. So, let's say button will be below the imageView first. In this case, you need to set imageView to button constraint's priority to something like 750 or UILayoutPriorityDefaultHigh and label to button constraint's priority to 250 or UILayoutPriorityDefaultLow.
Let's start creating a custom UITableViewCell
class YourTableViewCell: UITableViewCell {
#IBOutlet weak var imageView: UIImageView!
#IBOutlet weak var label: UILabel!
#IBOutlet weak var button: UIButton!
#IBOutlet weak var buttonToLabelConstraint: NSLayoutConstraint!
#IBOutlet weak var buttonToImageViewConstraint: NSLayoutConstraint!
override func awakeFromNib() {
super.awakeFromNib()
}
override func setSelected(selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
}
func shouldHideImageView(hidden: Bool) {
if(hidden == false) {
buttonToLabelConstraint.priority = UILayoutPriorityDefaultLow
buttonToImageViewConstraint.priority = UILayoutPriorityDefaultHigh
imageView.hidden = true
} else {
buttonToLabelConstraint.priority = UILayoutPriorityDefaultHigh
buttonToImageViewConstraint.priority = UILayoutPriorityDefaultLow
imageView.hidden = false
}
self.contentView.layoutIfNeeded()
}
}
After that, in your class where tableView is placed implement a logic like that:
if(row == 1) {
cell.shouldHideImageView(true)
} else {
cell.shouldHideImageView(false)
}
You should be all set.

Answer 2

You can try using a StackView, when you tell something to be hidden, the imageView the stack view will adjust the StackView as if the imageView was never a part of the view and it is an easy work around to not have to worry about constraints.

Answer 3

You can create IBOutlet on constraint and then just simply change the value like this:
buttonConstraint.constant = newValue
But i suggest you create for this a tableView. In this case you code and logic, i think, will be more accurate.

Answer 4

you could to this instead of hiding.
Make an outlet from the heights constraint of the imageview, call it constraint for now.
Set constraint.constant = 0 // effectively same as hiding.
Set constraint.constant = NON_ZERO_VALUE // effectively same as show.
hope it helps!

Answer 5

I see a couple of options. The first is a little easier to implement but a little less flexible if you decide to change your layout later.
Make the button's constraint to be below the label. Keep a reference to this constraint (you can connect it to your code via storyboard just like you do with the button itself, if you're using storyboard). When the imageView is visible, set myConstraint.constant += myImageView.frame.height. When the imageView is hidden, set myConstraint.constant -= myImageView.frame.height. Afterwards, call view.setNeedsLayout to update your constraints.
Make two constraints: one for below the image, and one for below the label ("constraintToImage" and "constraintToLabel"). Hook them both up to your controller like in option 1, and call view.addConstraint(constraintToImage) and view.removeConstraint(constraintToLabel) when the image becomes visible (and the opposite for when it's hidden). Again, call view.setNeedsLayout after.