So, we have done so many functions that I thought I could pull this off. I am helping my students create an app that will track their goals/scores on a test. They would put in their goal and then their score when the test was complete. I want that double to give me my trim value. I really thought I could pull what we did from Cupcake Corner to make this happen, but I'm floundering.

struct MMathView: View {

@AppStorage("mapBOY") var mapBOY: Int = 0
@AppStorage("mapBOYg") var mapBOYg: Int = 0

var setTrim: Double {
    var setTrim = Double(mapBOY/mapBOYg)
    return setTrim
}

  func setTrim() -> Double {
        return Double(mapBOY/mapBOYg)
        let result = setTrim()
    }

///// later I use it here

      Circle()// Beginning band-goal
                        .trim(from: 0, to: setTrim)
                        .stroke(lineWidth: 40)
                        .frame(width: 450)
                        .rotationEffect(.init(degrees: -90))

So it should fill it to 0.8 but it doesn't change the value at all. If I switch the values, I do get a full fill so the trim seems to be getting a value... just not the right way?

Integer division throws away any remainder, so, depending on the values you feed it, your mapBOY/mapBOYg is often going to end up as 0. Which when you convert to a Double, becomes 0.0. As in the example where you are expecting 0.8; you will never get that as an answer when converting the result of integer division to a Double.

As @roosterboy says is true change the computed property to this

var setTrim: Double {
    Double(mapBOY) / Double(mapBOYg)
}

So you can do this

struct ContentView: View {
    @AppStorage("mapBOY") var mapBOY: Int = 8
    @AppStorage("mapBOYg") var mapBOYg: Int = 10

    var setTrim: Double {
        Double(mapBOY) / Double(mapBOYg)
    }

    var body: some View {
        ZStack {
            Circle()
                .stroke(Color.blue.opacity(0.2), style: StrokeStyle(lineWidth: 40, lineCap: .round))
                .frame(width: 300)
                .rotationEffect(.init(degrees: -90))

            Circle()
                .trim(from: 0.0, to: setTrim)
                .stroke(Color.blue.gradient, style: StrokeStyle(lineWidth: 40, lineCap: .round))
                .frame(width: 300)
                .rotationEffect(.init(degrees: -90))

        }
    }
}

Thank yall! I appreciate it. Order of operations got me!