How to stop recreating @state variable after recreating view in SwiftUI-CodePudding

@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?

CodePudding user response：

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

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

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

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

CodePudding user response：

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()
    }
}