WeView Example

UIButton *button = ...;
UIView *superview = ...;
NSDictionary *variableMap = NSDictionaryOfVariableBindings(label, superview);
NSLayoutConstraint *cn = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[button]-12-[superview]"
                                                                 options:0
                                                                 metrics:nil
                                                                   views:variableMap];
[superview addConstraint:cn];
cn = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[superview]-(<=1)-[button]"
                                             options:NSLayoutFormatAlignAllCenterY
                                             metrics:nil
                                               views:variableMap];
[superview addConstraint:cn];