ios - Make constraints for subviews programatically -

i need create uislider , put above existing slider.

i know how create constraints view if want attach it's superview:

        uiview *superview = view.superview;         [view setvalue: [nsnumber numberwithbool: false] forkey: @"translatesautoresizingmaskintoconstraints"];          nslayoutconstraint *topconstraint =[nslayoutconstraint                                             constraintwithitem: view                                             attribute:nslayoutattributetop                                             relatedby:nslayoutrelationequal                                             toitem: superview                                             attribute:nslayoutattributetop                                             multiplier:1.0                                             constant:0.0];         nslayoutconstraint *bottomconstraint =[nslayoutconstraint                                                constraintwithitem: view                                                attribute:nslayoutattributebottom                                                relatedby:nslayoutrelationequal                                                toitem: superview                                                attribute:nslayoutattributebottom                                                multiplier:1.0                                                constant:0.0];         nslayoutconstraint *leadingconstraint =[nslayoutconstraint                                                 constraintwithitem: view                                                 attribute:nslayoutattributeleading                                                 relatedby:nslayoutrelationequal                                                 toitem: superview                                                 attribute:nslayoutattributeleading                                                 multiplier:1.0                                                 constant:0.0];         nslayoutconstraint *trailingconstraint =[nslayoutconstraint                                                  constraintwithitem: view                                                  attribute:nslayoutattributetrailing                                                  relatedby:nslayoutrelationequal                                                  toitem: superview                                                  attribute:nslayoutattributetrailing                                                  multiplier:1.0                                                  constant:0.0];         nsarray *constraints = @[topconstraint, bottomconstraint, leadingconstraint, trailingconstraint];         [superview addconstraints: constraints]; 

but same method not work when need attach 2 subviews together. say, have view1 subview of superview. has been created time ago. need 1 (view2) have same positioning inside superview.

something like

        uiview *superview = view1.superview;          uiview *view2 = [[uiview alloc] init];         [superview addsubview: view2];          [view2 setvalue: [nsnumber numberwithbool: false] forkey: @"translatesautoresizingmaskintoconstraints"];          nslayoutconstraint *topconstraint =[nslayoutconstraint                                             constraintwithitem: view1                                             attribute:nslayoutattributetop                                             relatedby:nslayoutrelationequal                                             toitem: view2                                             attribute:nslayoutattributetop                                             multiplier:1.0                                             constant:0.0];         nslayoutconstraint *bottomconstraint =[nslayoutconstraint                                                constraintwithitem: view1                                                attribute:nslayoutattributebottom                                                relatedby:nslayoutrelationequal                                                toitem: view2                                                attribute:nslayoutattributebottom                                                multiplier:1.0                                                constant:0.0];         nslayoutconstraint *leadingconstraint =[nslayoutconstraint                                                 constraintwithitem: view1                                                 attribute:nslayoutattributeleading                                                 relatedby:nslayoutrelationequal                                                 toitem: view2                                                 attribute:nslayoutattributeleading                                                 multiplier:1.0                                                 constant:0.0];         nslayoutconstraint *trailingconstraint =[nslayoutconstraint                                                  constraintwithitem: view1                                                  attribute:nslayoutattributetrailing                                                  relatedby:nslayoutrelationequal                                                  toitem: view2                                                  attribute:nslayoutattributetrailing                                                  multiplier:1.0                                                  constant:0.0];         nsarray *constraints = @[topconstraint, bottomconstraint, leadingconstraint, trailingconstraint];         [superview addconstraints: constraints]; 

breaks everything. please help.

looks have backward...

you want constrain view2 to view1:

[nslayoutconstraint     constraintwithitem: view2    // <-- constrain view     attribute:nslayoutattributetop     relatedby:nslayoutrelationequal     toitem: view1               //  <-- view     attribute:nslayoutattributetop     multiplier:1.0     constant:0.0];