Same array binded to two SwiftUI Views hangs-up App when object deleted

Question

I try to build an app in MacOS SwiftUI, where two different subviews of main contentView shows different parts of Axis element:

struct ContentView: View {
    @Binding var document: GlyphDesignerDocument
    
    var body: some View {
        HStack {
            #warning("if AxesSlidersView is not commented, and Axis will be deleted — program explodes")
            AxesSlidersView(axes: $document.axes)
            AxesView(axes: $document.axes,
                     addRows: {document.axes.insert(Axis("z", bounds: 0...1000), at: $0)},
                     removeRows: {document.axes.remove(at: $0)},
                     addAxis: {document.axes.append(Axis("z", bounds: 0...1000))})     
        }
    }

Subviews works great, everything updates in both ways, but application hangs-up when AxisView will delete one Axis from axes array.

All code is available at https://github.com/typoland/GlyphDesignerTest AxesView looks like this:

struct AxesView : View {
    @Binding var axes: [Axis]
    @State var selected: Int? = nil
    var addRows: (_ at:Int) -> Void
    var removeRows: (_ at: Int) -> Void
    var addAxis: () -> Void
    var body: some View {
        VStack {
            .... Shows Axes
        }
    }
}

struct AxisView: View {
    
    @Binding var axis: Axis
    var insert: () -> Void
    var delete: () -> Void
    @Binding var selected: Bool
    
    var body: some View {
        HStack {
            .... Shows one Axis
        }
    }
}
struct AxesSlidersView: View {
    @Binding var axes: [Axis]
    var body: some View {
        VStack {
            .... Shows Axes
        }
    }
}

Is it SwiftUI problem? How to deal with this?

Github version, whole small app looks like this:

Asperi · Accepted Answer · 2020-11-17 17:24:38Z

2

I recall there were problems with direct binding with onDelete. Try with proxy binding in AxesSlidersView as below:

Slider(value: Binding(get: { axes[index].at }, set: {axes[index].at = $0}), in: axes[index].bounds)
    .frame(idealWidth: metrics.frame(in: .global).width*0.6)

answered Nov 17, 2020 at 17:24

Asperi

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3 Comments

Łukasz Over a year ago

I know, this is not place to say „Thank You” but „Thank You”. At least one week I tried to solve this problem.

Łukasz Over a year ago

But now changes made on .at in SlidersView are not reflected in AxesView...

Łukasz Over a year ago

When I made proxy in upper view Binding(get: {axes[index]}, set:{axes[index] = $0}) it started to work as should. Could you edit your answer, please?

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