Check out How to set height programmatically autolayout by JR. Here is an excerpt:
You can set the height and width visually like this.
NSArray *foo1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[clearSearchButton(==searchBar)]" options:0 metrics:nil views:views]; NSArray *foo2 = [NSLayoutConstraint...
The full article is available here.