Question 261409 in Xcode Question posted in
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Xcode – Picker with Menu does not work with Int32 but it works with Int

This code does not work, meaning onChange is never called and the variable is not changed when a dropdown option is selected.

struct ExamplePicker: View {
    
    @State var val: Int32 = 2
    
    var body: some View {
        HStack {
            
            Menu {
                
                Picker(selection: $val, label: EmptyView()) {
                    
                    Text("Val1").tag(1)
                    Text("Val2").tag(2)
                    Text("Val3").tag(3)
                }
                
                
            } label: {
                HStack {
                    Text("Value: ")
                    Spacer()
                    
                    Text(String(format: "%d", val))
                    
                    Spacer()
                }
                
            }
            .onChange(of: val) { newSelection in
               print(">>> HERE")
           }
            
            
        }
        
    }
}

but if you change val to type Int it works perfectly fine.
This looks like a bug to me

EDIT:
Solved – the problem is that in .tag() you need the EXACT same type.
so .tag(1) would be Int not Int32. and thus .tag(Int32(1)) is needed

Tags:

2

Answers


  1. 0

    It works fine when the tag values of the Picker items have the same type as the state variable. Like this:

    Picker(selection: $val, label: EmptyView()) {
    Text("Val1").tag(Int32(1))
    Text("Val2").tag(Int32(2))
    Text("Val3").tag(Int32(3))
}
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  2. 0

    When you do .tag(1), the type of 1 is Int. tag does not know anything about what type of Binding you have passed to selection: – any Hashable thing can go in there:

    func tag<V>(_ tag: V) -> some View where V : Hashable

    By type inference, 1 in tag(1) is inferred to be Int, because I repeat, tag doesn’t know anything about selection:.

    So the type of the selection: binding is different from the type of the tag. This means that when you select something in the picker, SwiftUI doesn’t know what it should change the selection value to. It also doesn’t know which option is currently selected, for the same reason.

    To make a Int32 selection work, explicitly say that 1, 2, 3 etc are Int32s:

    Text("Val1").tag(Int32(1))
Text("Val2").tag(Int32(2))
Text("Val3").tag(Int32(3))
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