Stanislav Smida Stanislav Smida - 9 months ago 87
iOS Question

Auto Layout: layoutMarginsGuide

How to rewrite visual format

addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("|-[label]-|", options: .AlignAllBaseline, metrics: nil, views: ["label": label]))
addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[label]-|", options: .AlignAllCenterX, metrics: nil, views: ["label": label]))

by moving to layout guides (with margins)?

I tried it with

label.topAnchor.constraintEqualToAnchor(layoutMarginsGuide.topAnchor).active = true
label.leftAnchor.constraintEqualToAnchor(layoutMarginsGuide.leftAnchor).active = true
label.bottomAnchor.constraintEqualToAnchor(layoutMarginsGuide.bottomAnchor).active = true
label.rightAnchor.constraintEqualToAnchor(layoutMarginsGuide.rightAnchor).active = true

but does not work. Even
does not have expected value (yes I call it in
is executed). Constraints are set, but acts like there is zero margin. It layouts and gives expected
only when the layout margin is set to negative; which is not what I want obviously, but demonstrates that constraints are set with margins guides. Looks like I'm missing something...

Answer Source

It seems to me that layoutMarginsGuide is not ready in the init method of a UIView. I'm also getting similar issues, where setting up the constraints in updateConstraints just works. Still investigating why.

UPDATE: What I was trying to do was set the layoutMargins before the view had been added to a superview (in the init). That didn't work. What did work was setting the constraints in the init, relative to layoutMarginsGuide, but actually setting the layoutMargins in viewDidMoveToSuperView.