On Fri, Oct 4, 2013, at 08:22 PM, Luther Baker wrote: > First of all ... very much appreciate you both so often! Thanks for > commenting as much as you do. > > I too faced this issue and, like Kyle, read enough to assume it was > generally not possible with VFL. But this afternoon, I came across this: > https://github.com/evgenyneu/center-vfl and for my specific case, it > works > perfectly. Let me know what you think ... and if you see caveats. I'm > successfully using this technique to center an ImageView populated with > an > image much larger than the iPhone's screen on a simple, standard plain > old > ViewController's view.
This doesn't work on OS X, and I'm surprised it works on iOS. > UIView *superview = self.view; > NSDictionary *variables = > NSDictionaryOfVariableBindings(label, superview); > NSArray *constraints = [NSLayoutConstraint > constraintsWithVisualFormat:@"V:[superview]-(<=1)-[label]" > options: > NSLayoutFormatAlignAllCenterX > metrics:nil > views:variables]; > [self.view > addConstraints:constraints]; This specifies a relationship between the superview's bottom edge and the label's top edge, yet the label is a subview of the superview. When running on the Mac, I would expect NSLayoutConstraint to complain here , but I can see why it might not if the "|-" syntax is treated as a simple shortcut for whatever the superview happens to be. Indeed, if you try the equivalent on the Mac, you can see that this code throws an exception because it tries to install a constraint relating a view to another view upon that view itself: """ Unable to install constraint on view. Does the constraint reference something from outside the subtree of the view? That's illegal. constraint:<NSLayoutConstraint:0x104406a00 V:[NSView:0x10060da80]-(<=1)-[NSTextField:0x10012ac00]> view:<NSView: 0x10060da80> """ I've forked the project you linked to and uploaded my demo: <https://github.com/kylesluder/center-vfl/> Also, I suspect the reason you're specifying center-X alignment when creating the vertical constraints is because NSLayoutConstraint threw an exception when you tried to use the center-Y alignment option. That should be warning enough. ;-) --Kyle Sluder _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
