Lazy wont work! Cannot use instance member 'field' within property initializer; property initializers run before 'self' is available

Question

I'm trying to make a form that will have something to type in (str), a TextField to type it in to and some text below (var = correct) to let me know if I have it correct so far.

For example, (str) = "hello world", if "hel" is in the text field the text below will read "True". The issue is that I can't seem to get correct to use (str) and (field). I've seem similar questions on here that are solved with 'lazy', but that wont work, because ("Property 'field' with a wrapper cannot also be lazy").

func stringSlice(string: String, first: Int, last: Int)->String{
    var newStr = ""
    for number in 0..<string.count{
        if first <= number{
            if number <= last{
                newStr += "\(string[string.index(string.startIndex, offsetBy: number)])"
            }
        }
    }
    return newStr
}


func checkSoFar(answer: String, guess: String)->String{
    if stringSlice(string: answer, first: 0, last: guess.count) == guess{
        return "True"
    }
    return "False"
}


struct thisView: View{
    var str = "Hello world!"
    @State private var field = ""
    @State private var correct = checkSoFar(answer: str, guess: field)
    var body: some View{
        Form{
            Text(self.str)
            TextField("Type the above", text: $field){
            }
            Text(correct)
        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        thisView()
    }
}

Any ideas would be greatly appreciated. Thank you.

Joakim Danielson Joakim Danielson · Accepted Answer · 2020-01-13T10:28:29

The simplest solution would be to remove the correct property and do

var body: some View{
    Form{
        Text(self.str)
        TextField("Type the above", text: $field){
        }
        Text(checkSoFar(answer: str, guess: field))
    }
}

But maybe this could also be a way forward: to call the checkSoFar function when a button is pressed

struct thisView: View{
    var str: String = "Hello World!"
    @State private var field: String = ""
    @State private var correct: String = ""

    init(answer: String) {
        str = answer
    }

    var body: some View{
        Form{
            Text(self.str)
            TextField("Type the above", text: $field){
            }
            Text(correct)
            Button("Try") {
                self.correct = checkSoFar(answer: self.str, guess: self.field)
            }

        }
    }
}

Lazy wont work! Cannot use instance member 'field' within property initializer; property initializers run before 'self' is available

1 Answers