objective c - constraints cause an ambiguousLayout -
    i have nswindow  instance have setupui  method.   -(void) setupui {     nsview* subview = [[nsview alloc] initwithframe:nszerorect];     subview.wantslayer = yes;     subview.layer.backgroundcolor = [[nscolor greencolor] cgcolor];     [self.contentview addsubview:subview];     [self.contentview settranslatesautoresizingmaskintoconstraints:no];     [self.contentview addconstraint:[nslayoutconstraint constraintwithitem:self.contentview                               attribute:nslayoutattributeleading                               relatedby:nslayoutrelationequal                                  toitem:subview                               attribute:nslayoutattributeleading                              multiplier:1                                constant:0]];     [self.contentview addconstraint:[nslayoutconstraint constraintwithitem:self.contentview                               attribute:nslayoutattributetop                               relatedby:nslayoutrelationequal                 ...