auto layout modify multiplier of constraint programmatically

Question

How can I modify the multiplier of a constraint programmatically? I have set the following:

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_         


        

Answer 1

For modifying multiplier I use switching between constraints method.
You must Create constraints with different priorities else it will break the layout.

Objective C

NSLayoutConstraint *constraint1, *constraint2;

// switch between constraints

constraint1.active = NO; 
constraint2.active = YES;
[self.view layoutIfNeeded];

Swift 2.0

self.constraint1.active = true
self.constraint2.active = false
self.view.layoutIfNeeded()