How to outlet constraints and animate constraint changes

Constraints

[self.view layoutIfNeeded]; // always call on self.view
_constraintObject.constant = 44; // change the constraint value
[UIView animateWithDuration:0.25
				animations:^{
					[self.view layoutIfNeeded]; // call again to update the layout
				}];

sources:
http://stackoverflow.com/questions/12622424/how-do-i-animate-constraint-changes
http://stackoverflow.com/questions/22086054/unable-to-make-outlet-connection-to-a-constraint-in-ib