I've created a height constraint for a UIView in the Interface Builder that sets the height to = the superview. I set the multiplier to 1/3 of the superview's width. This works great, it sets the height, say on iPhone 5/5S, to ~107pts.
For wider screens, I want to set the multiplier to 1/4 instead; I suppose I could do this with Size Classes, but I'm not sure that's the best way to go for this?
In my viewWillAppear method of a view controller, I've tried doing the following; no matter what I do though, it still sets the height to only ~107pts. Note that _controlsAspectRatio is an IBOutlet to the IB constraint.
_controlsAspectRatio = [NSLayoutConstraint constraintWithItem:_controlsAspectRatio.firstItem attribute:_controlsAspectRatio.firstAttribute relatedBy:_controlsAspectRatio.relation toItem:_controlsAspectRatio.secondItem attribute:_controlsAspectRatio.secondAttribute multiplier:1.0f/4.0f constant:0];
// I've tried several combinations of several layout refresh options, to no avail
[_controlsContainer setNeedsUpdateConstraints];
[_controlsContainer setNeedsLayout];
[_controlsContainer layoutIfNeeded];
NSLog(@"%0.4f - %0.4f", _controlsContainer.frame.size.height, _controlsAspectRatio.multiplier);
// Output: 106.6667 - 0
Had to remove the original and add a completely new constraint:
NSLayoutConstraint* newControlsAspectRatio = [NSLayoutConstraint constraintWithItem:_controlsAspectRatio.firstItem attribute:_controlsAspectRatio.firstAttribute relatedBy:_controlsAspectRatio.relation toItem:_controlsAspectRatio.secondItem attribute:_controlsAspectRatio.secondAttribute multiplier:1.0f/4.0f constant:0];
[self.view removeConstraint:_controlsAspectRatio];
[self.view addConstraint:newControlsAspectRatio];
[_controlsContainer layoutIfNeeded];
NSLog(@"%0.4f - %0.4f", _controlsContainer.frame.size.height, newControlsAspectRatio.multiplier);
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