How can I modify the multiplier of a constraint programmatically? I have set the following:
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0]];
and I need to modify it to this:
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
As others said, you have to delete the old one and add a new one. If you do not want to store it as a property, just set identifier and search to get it later
-(NSLayoutConstraint *)constraintWithIndientifer:(NSString *)identifer InView:(UIView *)view{
NSLayoutConstraint * constraintToFind = nil;
for (NSLayoutConstraint * constraint in view.constraints ) {
if([constraint.identifier isEqualToString:identifer]){
constraintToFind = constraint;
break;
}
}
return constraintToFind;
}
Then
NSLayoutConstraint * constraint = [NSLayoutConstraint constraintWithItem:self.yellowView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0];
constraint.identifier = @"1234";
[self.view addConstraint:constraint];
Then you can get this
NSLayoutConstraint * constraint = [self constraintWithIndientifer:@"1234" InView:self.view];