SwiftUI: Change ForEach source or fetch request using Picker (Segmented)

Question

I'm new to SwiftUI and coding in general, so sorry if this has being covered before. I did search about it but I couldn't find it clear enough.

I'm trying to make an app for storing notes and tasks. (I'm not planning to put it on the store, I'm too newbie for that, but I do want to learn Swift and working on an actual app is more useful to me than reading about it.) I have an entity called "Base" with 8 attributes and automatic Codegen Class Definition selected. I prefer to keep it that way, no manual please.

I have three fetch requests. One gets me all data from Core Data. The other two filter one attribute called campoEstado. For now in campoEstado I only store one of two possible values, as strings: "Activas", and "Pospuestas". In the future I may add more so I can't use a boolean for this.

I get a List working with one fetch request. But I can't change that source when the app is running. I made a Picker with .pickerStyle(SegmentedPickerStyle()) that shows me: Todo, Activas, Pospuestas. When the user selects one of this tabs in the picker the list should change to:

• Tab 1: All tasks
• Tab 2: A filtered list containing only tasks with campoEstado = "Activas" (calls the fetch request filtroActivas)
• Tab 3: A filtered list containing only tasks with campoEstado = "Pospuestas" (calls the fetch request filtroPospuestas)

How it should look:

My code in ContentView:

    struct ContentView: View {    

@Environment(\.managedObjectContext) var moc    
    @FetchRequest(entity: Base.entity(), sortDescriptors: [
        NSSortDescriptor(keyPath: \Base.campoNota, ascending: true),
        NSSortDescriptor(keyPath: \Base.campoFechaCreacion, ascending: true)
    ], predicate: NSPredicate(format: "campoEstado == %@", "Activas")
    ) var filtroActivas: FetchedResults<Base>

    @FetchRequest(entity: Base.entity(), sortDescriptors: [
        NSSortDescriptor(keyPath: \Base.campoNota, ascending: true),
        NSSortDescriptor(keyPath: \Base.campoFechaCreacion, ascending: true)
    ], predicate: NSPredicate(format: "campoEstado == %@", "Pospuestas")
    ) var filtroPospuestas: FetchedResults<Base>

     @FetchRequest(entity: Base.entity(), sortDescriptors: [
        NSSortDescriptor(keyPath: \Base.campoNota, ascending: true),
        NSSortDescriptor(keyPath: \Base.campoFechaCreacion, ascending: true)
    ]
    ) var bases: FetchedResults<Base>

var body: some View {
        NavigationView {
            List {
                Picker("Solapas", selection: $selectorIndex) {
                    //This should connect to ForEach source, currently "bases"
                }
                .pickerStyle(SegmentedPickerStyle())
                
              
                ForEach(bases, id: \.self) { lista in
                    NavigationLink(destination: VistaEditar(base: lista)) {
                        Rectangle()
                        .foregroundColor(.gray)
                        .frame(width: 7, height: 50)
                        
                        VStack(alignment: .leading) {
                            Text(lista.campoNota ?? "Unknown title")
                                .font(.headline)
                            Text(lista.campoEstado ?? "Activas")
                        }
                    }
                }

I have two problems:

1. I don't know how to connect the selected tab in the picker with the source of ForEach inside List

2. I made the list work for one fetch request, the one that brings me every record in Core Data, but I don't know how to change the ForEach source when the app is running. I have tried an array of names of variables for every one of the fetch requests variables names (bases, filtroActivas and filtroPospuestas) putting them in [] but that didn't work.

I know this isn't elegant, I just need it to work first and then go for efficiency and elegance. I'm sure there is some stupid thing I'm not seeing but it's been a week and I'm getting desperate.

I hope I was clear, if you need more information please ask. If anyone can help me I would very much appreciate it. Thanks in advance!

Answer 1

I worry I may get downvoted for this because it's not an entirely complete answer. But I'm out of time and I wanted to see if I could get you in the right direction.

What I believe you're looking for is an Array of Arrays. A FetchedResult will return an optional array, which you'll want to ensure isn't nil. I used compactMap in my example to generate non-nil array's of my sample optional arrays which are intended to simulate what you are getting back from your @FetchRequest properties. You should be able to load this code into a new project in Xcode to see the results. Again it's not a complete answer but will hopefully help you along in your project. I hope this helps, keep working at it, you'll get it!

struct ContentView: View {
// Sample data to mimic optional FetchedResults coming from CoreData.
// These are your @FetchRequest properties
let fetchedResultsBases: [String?] = ["Red", "Green", "Blue"]
let fetchedResultsFiltroPospuestas: [String?] = ["1", "2", "3"]
let fetchedResultsFiltroActivas: [String?] = ["☺️", "", ""]

// Options for your picker
let types = ["Bases", "Pospuestas", "Activas"]

@State private var groups = [[String]]()
@State private var selection = 0

var body: some View {
    NavigationView {
        VStack {
            Picker("Solapas", selection: $selection) {
                ForEach(0..<types.count, id: \.self) {
                    Text("\(self.types[$0])")
                }
            }.pickerStyle(SegmentedPickerStyle())

            List {
                ForEach(0..<groups.count, id: \.self) { group in
                    Text("\(self.groups[self.selection][group])")
                }
            }
        }
    }
    .onAppear(perform: {
        self.loadFetchedResults()
    })
} // This is the end of the View body

func loadFetchedResults() {
    // This is where you'll create your array of fetchedResults, then add it to the @State property.
    var fetchedResults = [[String]]()

    // Use compact map to remove any nil values.
    let bases = fetchedResultsBases.compactMap { $0 }
    let pospuestas = fetchedResultsFiltroPospuestas.compactMap { $0 }
    let filtroActivas = fetchedResultsFiltroActivas.compactMap { $0 }

    fetchedResults.append(bases)
    fetchedResults.append(pospuestas)
    fetchedResults.append(filtroActivas)

    groups = fetchedResults
}

} // This is the end of the ContentView struct