TIL: @State Initialization in SwiftUI

I’m building an iOS app for Askhole that shows a question out of a list of question. I’m using a basic @State private var property to store the index of the current question. I wanted to randomize this on launch, but @State private vars have to be initialized to a literal value, so instead I implemented this:

struct ContentView: View {
    private var questions: [Question]
    @State private var currentQuestion = 0

    init(questions: [Question]) {
        self.questions = questions
        currentQuestion = Int.random(in: 0 ..< questions.count)
    }
}

Turns out that does not work, due to the extra logic that comes with an @State property! Every time I tried running this, it showed the first question. What I had to do instead was initialize the property as a State value:

struct ContentView: View {
    private var questions: [Question]
    @State private var currentQuestion = 0

    init(questions: [Question]) {
        self.questions = questions
        _currentQuestion = State(initialValue: Int.random(in: 0 ..< questions.count))
    }
}