How to define variables inside a GeometryReader in SwiftUI

Question

I'd like to calculate the line width of a shape inside a view based on the view's size. Looking through various posts here on StackOverflow, I think the solution is to use a GeometryReader like this:

struct MyView: View {
    var body: some View {
        GeometryReader { geometry in
           // Here goes your view content,
           // and you can use the geometry variable
           // which contains geometry.size of the parent
           // You also have function to get the bounds
           // of the parent: geometry.frame(in: .global)
        }
    }
}

My question is, how can I define variables inside the GeometryReader construct to be used for the view? I've tried to put a var statement directly after the line "GeometryReader { geometry in", but this gives a compiler error.

Clarification: are you trying to find the dimensions of MyView, or its parent? Is MyView the "line width of a shape" (where GeometryReader would be the dimensions of the parent view) or is this "shape" a child View inside MyView? — user7014451
– user7014451, Commented Jul 16, 2019 at 22:19
Basically, don't forget the everything in SwiftUI is a View - it sounds like you are trying to work with a CAShapeLayer frame based on the UIView dimensions. — user7014451
– user7014451, Commented Jul 16, 2019 at 22:20
The answer bellow just solves what I'm trying to achieve. Thanks. — G. Marc
– G. Marc, Commented Jul 17, 2019 at 7:05

arsenius · Accepted Answer · 2019-07-16 23:55:02Z

16

This seems to be a function builder related bug (as of Beta 3), and I recommend filing feedback on it.

The workaround I've been using is to use GeometryProxy in a separate method with an explicit return.


var body: some View {
  GeometryReader { proxy in
    self.useProxy(proxy)
  }
}

func useProxy(_ proxy: GeometryProxy) -> some View {
  var width = proxy.size.width
  return VStack {
    // use width in here
  }
}

answered Jul 16, 2019 at 23:55

arsenius

13.4k7 gold badges65 silver badges82 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

joshd Over a year ago

I believe I'm still seeing this in beta 7.

Collectives™ on Stack Overflow

How to define variables inside a GeometryReader in SwiftUI

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related