How to change array index in SwiftUI

Question

I have a page view that's calling an array's index to populate the page. When something happens I want to increment the index so it updates the page's content. In this code example, I have this happening upon button press. In my real app, I'll want this to happen when the timer reaches 0 but I suspect that if I can figure out how to get this button press version to work I can extrapolate this to my real use case. Here is the simple code for your review:

import SwiftUI

struct LanguageStruct: Identifiable {
    var id = UUID()
    var groupTitle: String
    var title: String
    var subTitle: String
    var image: String
}

var progLanguages = [
    LanguageStruct(groupTitle: "Java", title: "Lame Langauge", subTitle: "Bad GUI", image: "Push-ups Wide"),
    LanguageStruct(groupTitle: "SwiftUI", title: "Nice and New", subTitle: "Better than Swift but incomplete", image: "Sit-ups")
]

struct Playground_arrays: View {
    
    @State private var index = 0
    var programming: LanguageStruct
    
    var body: some View {
        VStack {
            Text(programming.groupTitle)
            Text (programming.subTitle)
            Image(programming.image)
            
            Button(action:{
                //actions go here
                if index < 2{
                    index += 1
                    
                }else{
                    index = 0
                }
            }, label:{
                Text("Change Index")
                    .fontWeight(.semibold)
            })
            .buttonStyle(PrimaryButtonStyle(buttonColor: "PositiveGreen"))
        }
    }
}

struct Playground_arrays_Previews: PreviewProvider {
    static var previews: some View {
        Playground_arrays(programming: progLanguages[0])
            .previewDevice("iPhone 12 mini")
    }
}

Can someone please help me figure out how to update the array's index upon button press so I can update the pages content? This seems like it should really be as simple as taking the above index var counter and placing it in the programing: progLanguages[index] string or something but I can't for the life of me figure out how to make it work :(

Eugene Dudnyk · Accepted Answer · 2021-10-19 08:32:22Z

2

Just have programming as a dynamic getter:

struct Playground_arrays: View {
    @State private var index = 0

    var programming: LanguageStruct {
        progLanguages[index]
    }
    
    var body: some View {
        VStack {
            Text(programming.groupTitle)
            Text (programming.subTitle)
            Image(programming.image)
            
            Button(action:{
                //actions go here
                if index < progLanguages.count - 1 {
                    index += 1
                } else {
                    index = 0
                }
            }, label:{
                Text("Change Index")
                    .fontWeight(.semibold)
            })
            .buttonStyle(PrimaryButtonStyle(buttonColor: "PositiveGreen"))
        }
    }
}

edited Oct 19, 2021 at 8:32

answered Oct 19, 2021 at 1:16

Eugene Dudnyk

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2 Comments

Yrb Over a year ago

You beat me to the answer... @jammyman34, you are assuming that you were not updating your index. You were. You were just never updating your 'programming' var. By making it a computed property, you will get the updated language with each change of the index.

jammyman34 Over a year ago

Thank you Eugene and thank you @Yrb! That's why I'm not going to quit my day job as a UX designer! I didn't even know what Eugene wrote and what you said @Yrb was a thing that could be written.

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