ios - changing layout anchors of view on an action -

i have 1 upperlabel, 1 view , button.

in viewdidload() method have given layout constraints view. on tap of button need update constraints(i.e view should move downwards). how can that.

here code that. not working.

let keyview = uiview()  override func viewdidload() {      keyview.frame = cgrect(x: 0, y: 0, width: 100, height: 30)     keyview.backgroundcolor = uicolor.cyan     keyview.translatesautoresizingmaskintoconstraints = false     containerview.addsubview(keyview)     keyview.topanchor.constraint(equalto: upperlabel.bottomanchor , constant: 10).isactive = true     keyview.leadinganchor.constraint(equalto: containerview.leadinganchor, constant: 20).isactive = true     keyview.trailinganchor.constraint(equalto: containerview.trailinganchor, constant: -20).isactive = true     keyview.bottomanchor.constraint(equalto: keyview.topanchor, constant: keyview.frame.size.height).isactive = true } 

code in action follows.

  func buttonaction(sender: uibutton!) {      keyview.translatesautoresizingmaskintoconstraints = false     keyview.topanchor.constraint(equalto: upperlabel.bottomanchor, constant: cgfloat(i*50))     keyview.leadinganchor.constraint(equalto: containerview.leadinganchor, constant: 20)     keyview.trailinganchor.constraint(equalto: containerview.trailinganchor, constant: -20)     keyview.bottomanchor.constraint(equalto: keyview.topanchor, constant: keyview.frame.size.height)     + =1 } 

as per above code keyview should move downwards on clicking of button. not moving down.

please me out. in advance.

take global variable of type nslayoutconstraint follows..

var keyviewtopconstraint: nslayoutconstraint?

now in viewdidload while giving initial constraints. give follows

    keyviewtopconstraint = keyview.topanchor.constraint(equalto: upperlabel.bottomanchor , constant: 10)     keyviewtopconstraint?.isactive = true 

now in action. remove initial constraint , create constraint , make active. follows

   keyviewtopconstraint?.isactive = false    keyviewtopconstraint = keyview.topanchor.constraint(equalto: upperlabel.bottomanchor, constant: cgfloat(i*50))    keyviewtopconstraint?.isactive = true