how do I implement func calculation inside struc?

user_16444504 0
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I am trying to create an apple watch app that calculates Karvonen value.

When I inserted func calculation into struct, I kept receiving the Swift Compiler Error that says:

[Type "FourthView"does not conform to protocol "View"]

I understood that I should not be calculating inside the func, but I don't know how to solve this problem.

struct FourthView: View{

    @Binding var fourthScreenShown:Bool
    //@State var RHR:Int
    //@State var weight:Int
    @State var Age:Int
    @State var ExerciseIT = 0.3
    @State var ConstantNumber = 220
    @State var RHR = 68
    
    func karvonen(cn: Int, rhr: Int, age: Int, ei:Double) -> Double {
        return Double((cn-age-rhr)) * ei + Double(rhr)
        let output = karvonen(cn: ConstantNumber, rhr: RHR, age: Age, ei: ExerciseIT)
        
        var body: some View {
            VStack{
                Text("Your Kar is")
                    .font(.system(size: 14))
                Text("\(output)")
                    .font(.system(size: 40))
            
            }
        }
    }
}
swiftui-navigationlink swiftui swift
1 Answers

The var body has to exist at the top level of the struct for it to conform to View. Right now, you have var body inside your func.

struct FourthView: View{
    
    @Binding var fourthScreenShown:Bool
    @State var Age:Int
    @State var ExerciseIT = 0.3
    @State var ConstantNumber = 220
    @State var RHR = 68
    
    func karvonen(cn: Int, rhr: Int, age: Int, ei:Double) -> Double {
        return Double((cn-age-rhr)) * ei + Double(rhr)
    }
    
    var body: some View {
        VStack{
            Text("Your Kar is")
                .font(.system(size: 14))
            Text("\(karvonen(cn: ConstantNumber, rhr: RHR, age: Age, ei: ExerciseIT))")
                .font(.system(size: 40))
        }
    }
    
}

Another equivalent version (maybe useful if you have to use the result in multiple places):

var body: some View {
    let output = karvonen(cn: ConstantNumber, rhr: RHR, age: Age, ei: ExerciseIT)
    VStack{
        Text("Your Kar is")
            .font(.system(size: 14))
        Text("\(output)")
            .font(.system(size: 40))
    }
}

Unrelated to your issue, but a hint for the future: in Swift, generally, variables/parameters are camel cased. So, your Age, ExerciseIT, etc would be age, exerciseIT, etc.

Also, unless you're changing the values, you don't need @State in front of all of the parameters. ConstantNumber, for example (if the name is accurate), probably doesn't need to be @State.

user_5609420
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