How to Update NSLayoutConstraint in StoryBoard?

Question

I created 2 Button in my superView , Now I want change the @IBOutlet weak var bottomLayOut: NSLayoutConstraint! depend on the user role .

the example is: if the user is a agent role but not a teacher role I want update the NSLayoutConstraint 's second item from Teacher Entry .bottom to AgentEntry button's bottom .

is that posible?

Update :

solve this by turn translatesAutoresizingMaskIntoConstraints to true: e.g : teacherBtn.translatesAutoresizingMaskIntoConstraints = true than, we can use both constraints and code to change teacherBtn's frame

just wondering, why not you change the button name and color based on the role instead of changing constraints? — Julfikar, Aug 29 '17 at 02:35
let me understand a bit clearly.. let's say the user role is teacher, so you want to show the teacher button on top and agent button on bottom, isn't it? — Julfikar, Aug 29 '17 at 02:45
there are 3 patterns : both teacher and agent role - show both 2 button, only teacher role - show teacher button , only agent role - show agent button. — Neko, Aug 29 '17 at 02:48
ok not sure how you wanna do it but i can suggest using `setFrame:CGRectMake` . this one you can use for positioning the buttons and to hide buttons you can use `button.hidden = YES;` . I would recommend you not to mess up with constraint — Julfikar, Aug 29 '17 at 04:31
but once you used Autolayout, you can't use code to change the frame , right? — Neko, Aug 29 '17 at 05:21
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/153081/discussion-between-neko-and-mohammad-julfikar). — Neko, Aug 29 '17 at 05:37
Use autolayout programatically. case 1- If both teacher and agent role - dont hidden any button. case 2 - only teacher role - agent button make it hidden and make bottom constraint of teacher button isactive false. And give top constraint for that button(programatically). 3 - only agent role - Just hidden the teacher button. — Pavankumar, Aug 29 '17 at 12:48

Charles Srstka · Answer 1 · 2017-08-30T01:38:05.060

Two ways I can think of to do this off the top of my head:

Set up the constraints programmatically. Create a property containing the current constraints on the buttons, and then you can do something along the lines of (disclaimer: written in Chrome, may contain typos, edit as appropriate):

` if let constraints = self.buttonConstraints { NSLayoutConstraint.deactivate(constraints) }

let views: [String : UIView] = ["Agent" : self.agentButton, "Teacher" : self.teacherButton]

let newConstraints: [NSLayoutConstraint] = {
    switch role {
    case .teacherAndAgent:
        self.teacherButton.isHidden = false
        self.agentButton.isHidden = false
        return NSLayoutConstraint.constraints(withVisualFormat: "V:[agent]-[teacher]-|", metrics: nil, views: views)
    case .teacherOnly:
        // you get the idea
    case .agentOnly:
        // ditto
    }
}()

NSLayoutConstraint.activate(newConstraints)
self.buttonConstraints = newConstraints`

What might be simpler, though, is to use a UIStackView to hold your buttons. On current macOS at least, NSStackView automatically adjusts the layout based on which of its views are hidden; if UIStackView on iOS behaves the same way, it may do a lot of the work for you without having to manually fuss with layout constraints.

How to Update NSLayoutConstraint in StoryBoard?

1 Answers1