Question 68458 in IOS Swift Question posted in
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Using SwiftUI with @AppStorage and on-the-fly function call – Ios swift

I am trying to use @AppStorage to read/save a value and calculate something with it, but I am failing to call a function within my ContentView. Example:

Helper.swift

func powerized(x: Decimal) -> Decimal {
    let powerized: Decimal  = pow(x, 3) * 6.25
    return powerized
}

ContentView.swift

import SwiftUI

struct ContentView: View {
  @AppStorage(StorageKeys.sourcePower.rawValue) var sourcePower = 15

  var body: some View {
     VStack {
         Text(powerized(x: sourcePower))
     }
   }
}

With this implementation, I get Initializer 'init(_:)' requires that 'Decimal' conform to 'StringProtocol'.

If I put a

var myValue: Decimal = powerized(x: sourcePower)
Text(myValue)

I get a conversion error Cannot convert value of type 'Int' to expected argument type 'Decimal'. This probably is because of the variable not defined as Decimal but even making that change I then get
Cannot use instance member 'age' within property initializer; property initializers run before 'self' is available.

I am getting quite mad with this. Is there any change to make it working without creating a new class with ObservableObject ? The AppStorage already solves for updating the UI every time it changes.
I think, as a workaround, in theory I can precalculate what I want with my function as store it as well as the source value, but it does not make any sense.

Tags:

2

Answers


  1. 0

    It has nothing to do with @AppStorage. Your powerized function returns a decimal, and you are trying to use is in a Text(). Text() requires a String. You can do:

      var body: some View {
     VStack {
         // Use .description which returns a String
         Text(powerized(x: sourcePower).description)
     }
   }

    Either of those will make it a String.

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  2. 0

    Because decimals are formatted differently in different countries (e.g. some use comma as a decimal point) you have to use a formatter and there is a new convenience API for that:

    Text(powerized(x: sourcePower), format: .number)

    This way the label will also update automatically if the region settings change.

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