SwiftUI: Find element position in array

Question

I'm still trying to get my head around Swift/SwiftUI, so apologies for what's likely a really simple question. Consider this simple SwiftUI file:

import SwiftUI

struct sampleStruct {
    let entryID: Int // comes from the system
    let name: String
}


struct TestView: View {
    
    var listEntries = [sampleStruct(entryID: 301, name: "Pete"),
                       sampleStruct(entryID: 5003, name: "Taylor"),
                       sampleStruct(entryID: 13, name: "Suzie")]
    
    var body: some View {
        VStack{
            ForEach(listEntries, id: \.entryID) { idx in
                Text(idx.name)
            }
        }
    }
}

struct TestView_Previews: PreviewProvider {
    static var previews: some View {
        TestView()
    }
}

Here's my question: I'm looking for a simple way to add the position of the element in the array to the text field. Ie instead of Pete, Taylor, Susie, I'd like to get:

1 Pete

2 Taylor

3 Suzie

I thought that this could do the trick:

...
VStack{
            ForEach(listEntries, id: \.entryID) { idx in
                Text( listEntries.firstIndex { $0.id == idx.entryID } )
                Text(idx.name)
            }
        }
...

But, I'm getting the error "No exact matches in call to initializer".

Any help would be appreciated,

Philipp

Answer 1

The simplest approach would be to use enumerated() , which returns a sequence of pairs (index and item):

struct TestView: View {
    
    var listEntries = [sampleStruct(entryID: 301, name: "Pete"),
                       sampleStruct(entryID: 5003, name: "Taylor"),
                       sampleStruct(entryID: 13, name: "Suzie")]
    
    var body: some View {
        VStack{
            ForEach(Array(listEntries.enumerated()), id: \.1.entryID) { (index,item) in
                Text("\(index + 1) \(item.name)")
            }
        }
    }
}

Note that for extremely large collections you might want a different approach for performance reasons, but for anything reasonably sized, this will work well. A quick and easy upgrade to it would be to used indexed() from Swift Algorithms in place of .enumerated() (you could omit the Array(...) wrapper if you did this as well.

---

If for learning purposes you want to see what you'd have to do to adjust your original approach, you'd want to:

1. Use .entryID instead of .id , which doesn't exist on your model
2. Provide a default index in case firstIndex returns nil
3. Interpolate the result into a String

One solution might look like this:

struct TestView: View {
    
    var listEntries = [sampleStruct(entryID: 301, name: "Pete"),
                       sampleStruct(entryID: 5003, name: "Taylor"),
                       sampleStruct(entryID: 13, name: "Suzie")]
    
    var body: some View {
        VStack{
            ForEach(listEntries, id: \.entryID) { item in
                let index = listEntries.firstIndex { $0.entryID == item.entryID } ?? -1
                Text("\(index + 1) \(item.name)")
            }
        }
    }
}