ios - How do I add a constraint such that a view is as wide as the widest of two other views? -

for example, labels a, b , c. label should have width of whichever wider, b or c.

visually, along lines of

@"h:[viewa(==max(viewb,viewc))]" 

if want ensure viewa simultaneously @ least wide both viewb , viewc, use 2 separate vfl statements, @"h:[viewa(>=viewb)]" , @"h:[viewa(>=viewc)]".

if want ensure not wider maximum width of viewb and/or viewc, define optional constraint (i.e. lower priority uilayoutpriorityrequired) width of viewa equal 1 of them, e.g.:

nslayoutconstraint *constraint = [nslayoutconstraint constraintwithitem:viewa                                                               attribute:nslayoutattributewidth                                                               relatedby:nslayoutrelationequal                                                                  toitem:viewb                                                               attribute:nslayoutattributewidth                                                              multiplier:1.0                                                                constant:0.0]; constraint.priority = uilayoutprioritydefaultlow; [viewa.superview addconstraint:constraint]; 

according documentation priority:

if constraint 'a == b' optional, constraint-based layout system attempt minimize 'abs(a-b)'.

thus, if viewb larger viewc, optional constraint satisfied , viewa wide viewb. if viewb smaller viewc, constraint system satisfy required @"h:[viewa(>=viewc)]" constraint, minimize abs(a-b), making viewa same width viewc.

in practice, don't need optional viewa==viewb constraint, if want ensure viewa won't wider both viewb , viewc, add final optional constraint.