Iterating an object array and changing values? - swiftui

Question

Used this scenario as an example to be a bit more self explanatory. I have a struct which represents a character, and one of the structs attributes is another struct: Stats (where I used id to represent the name in a more simple way).
Besides that I have a view with a ForEach, where I iterate over some Characters and I need to be able to increase a specific stat.
The problem is: I'm trying to increase stat.points using a button, but I keep getting the message "Left side of mutating operator isn't mutable: 'product' is a 'let' constant".
struct Character: Identifiable {
var id: String
var name: String
var stats: [Stats]
}
struct Stats: Identifiable {
var id: String
var points: Int
}
ForEach(characters.stats) { stat in
HStack {
Text("\(stat.id)")
Button {
stat.points += 1
} label: {
Text("Increase")
}
}
}
How could I make this work?

Answer 1

As you have found, structs in your stats: [Stats] does not allow changes
especially in a ForEach where it is a let.
There are many ways to achieve what you want, depending on what you trying to do.
This example code shows the most basic way, using the array of stats: [Stats]
directly:
struct ContentView: View {
#State var characters = Character(id: "1",name: "name-1", stats: [Stats(id: "1", points: 1),Stats(id: "2", points: 1)])
var body: some View {
ForEach(characters.stats.indices, id: \.self) { index in
HStack {
Text("\(characters.stats[index].id)")
Button {
characters.stats[index].points += 1
} label: {
Text("Increase")
}
Text("\(characters.stats[index].points)")
}
}
}
}
Here is another approach, using a function, to increase your stat points value:
struct ContentView: View {
#State var characters = Character(id: "1", name: "name-1", stats: [Stats(id: "1", points: 1), Stats(id: "2", points: 1)])
var body: some View {
ForEach(characters.stats) { stat in
HStack {
Text("\(stat.id)")
Button {
increase(stat: stat)
} label: {
Text("Increase")
}
Text("\(stat.points)")
}
}
}
func increase(stat: Stats) {
if let index = characters.stats.firstIndex(where: {$0.id == stat.id}) {
characters.stats[index].points += 1
}
}
}