CODEWITHSUNDEEP
iosobjective-cautolayoutconstraintsadaptive-layout
BlackM
BlackM

Reputation: 4065

iOS 8 - Find constraints for a UIView with identifier

I am trying to change a constraint for an ImageView for iPhone 4S,5,5S in viewDidLoad:

for (NSLayoutConstraint *constraint in logoImage.constraints) {
    if ([constraint.identifier isEqualToString:@"logoTopIdentifier"]) {
        constraint.constant=10;
    }
}

It seems that it's not even iterating in the loop. Is there any other way to get a specific constraint with identifier?

Upvotes: 7

Views: 3239

Answers (2)

Surely
Surely

Reputation: 1709

You can connect the constraint in storyboard to your view controller class same as connecting a UI element.

Just find the constraints in your storyboard, make the workspace into split view, and drag the constraint to your corresponding view controller class.

Sometimes if you want to animate the position change, you can update the constraint like:

self.theConstraint?.constant = 100 
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.7) { () -> Void in
    self.view.layoutIfNeeded()
}

block.

That is it.

Upvotes: 4

keshav vishwkarma
keshav vishwkarma

Reputation: 1852

Here is the KVConstraintExtensionsMaster library by which you can access the any constant from a view based on the NSLayoutAttribute. No matter whether that constraint added Programmatically or from Interface Builder.

 [self.logoImage accessAppliedConstraintByAttribute:NSLayoutAttributeTop completion:^(NSLayoutConstraint *expectedConstraint){
        if (expectedConstraint) {
            expectedConstraint.constant = 10;

            /* for the animation */ 
            [self.logoImage  updateModifyConstraintsWithAnimation:NULL];
      }
    }];

Upvotes: 2

Related Questions