I've done a lot of programming in the past, I'm just getting started with Swift and SwiftUI, so apologies if this is a silly question.

My first, playful, app is a BMI calculator. I have a class BMI, which conforms to ObservableObject and has properties bmi, weight and height. It has a function, calc() to calculate the BMI. bmi is @Published. The instance of BMI in ContentView is declared as @ObservedObject. When the "calculate bmi" button is pressed, the calc() method is called, it assigns a value to the bmi property and that is shown in its view. So far, so good.

The "calculate" button is modified by .disabled(bmi.shouldDisable()). The shouldDisable() function returns true if values have been entered into the weight and height fields.

My problem is that the shouldDisable() function isn't getting called when I enter stuff into the weight/height TextFields.

I'm obviously missing something here, which is probably simple: how do I get a View to be bound to a function, in the same way in which it can be bound to a variable?

Thanks in advance.

Jeremy

Add a computed property that check to see if a value has been entered in TextField

var validEntry: Bool {
  if Double(weight) = nil || Double(height) = nil {
    return true
  }
  return false
}

then on Button (in SwiftUI)

.disabled(validEntry)

Thanks. I had tried that and failed. However, I've changed the class to a struct and it works well now.

Jeremy