Question 68690 in IOS Swift Question posted in
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How to stop recreating @state variable after recreating view in SwiftUI – Ios swift

@State var myDict: [String: Double] = [:]

var body: some View {
    HStack(alignment: .top) {
        Button(action: {
            self.myDict[self.tag ?? ""] = amountValue
        }) 
    }
}

I have two user, when i select 1st user I add value to myDict, and when I select 2nd user I want to add another value to it (means myDict will have 2 object), but when i select 2nd user @state variable is refresh and have only one value of 2nd user. (means myDict have 1 object)

is there any way so that I can have both the value in dict not only one?

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2

Answers


  1. 0

    actually, this can happen that for both users self.tag is nil and ("") is used as a key for the dictionary

    self.myDict[self.tag ?? ""] = amountValue

    and if this happens you may want to make sure that self.tag is not nil

    I have created a test environment just like your case but I have

    import SwiftUI

struct swiftUIDoubt1: View {
    

    @State var myDict: [String: Double] = [:]
    
    var body: some View {
        VStack{
            Button(action: {
                myDict["Hello, World!"] = 9.99999
                print(myDict)
            }, label: {
                Text("(myDict["Hello, World!"] ?? 0)")
                    .padding()
            })
            
            Button(action: {
                myDict["bye, World!"] = 1.11111
                print(myDict)
            }, label: {
                Text("(myDict["bye, World!"] ?? 0)")
                    .padding()
            })
            
        }
        .onAppear(perform: {
            print(myDict)
        })
    }
}

    now as you can see when my screen will appear my dictionary should be empty and an empty dictionary must be printed, as you can see in the image
    console log when the app is first opened

    console log when app is first opened

    device screen when app is first opened

    when I click first button single item will be added and you can see in console log
    single item added

    and when I will click on the second button you can see I have two different items in my dictionary

    two items are added

    let success = "two different items has been added to dictionary"

    as @state variable to managed by swift UI and will not change with ui update

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  2. 0

    Small example : The add in the subview update the dictionnaire for the desired user in parent view

    import SwiftUI

struct UpdateUsersDict: View {
    @State var myDict: [String: Double] = [:]
    @State var amount: Double = 100
    var body: some View {
        VStack {
            HStack {
                OneUserView(myDict: $myDict, amount: amount, tag: "user 1")
                OneUserView(myDict: $myDict, amount: amount, tag: "user 2")
                OneUserView(myDict: $myDict, amount: amount, tag: "user 3")
            }
            HStack {
                Text("(myDict["user 1"] ?? -1)")
                Text("(myDict["user 2"] ?? -1)")
                Text("(myDict["user 3"] ?? -1)")
            }
        }
    }
}

struct OneUserView: View {
    @Binding var myDict: [String: Double]
    @State var amount: Double
    var tag: String

    var body: some View {
        HStack(alignment: .top) {
            Button(tag, action: {
                self.myDict[self.tag] = amount
            })
        }
    }
}

struct UpdateUserDict_Previews: PreviewProvider {
    static var previews: some View {
        UpdateUsersDict()
    }
}
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