I'm new to SwiftUI and when I use the onChange modifier I get the following error. Value of type 'some View' has no member 'onChange' Here's the section of my code and if I remove line 9 - 26 my code will compile.            GeometryReader{reader in             VStack {               Image("race2")                 .resizable()                 .aspectRatio(contentMode: .fill)                .frame(width: UIScreen.main.bounds.width, height: reader.frame(in: .global).minY > 0 ? reader.frame(in: .global).minY + (UIScreen.main.bounds.height / 2.2) : UIScreen.main.bounds.height / 2.2)                 .offset(y: reader.frame(in: .global).minY)                 .onChange(of: reader.frame(in: .global).minY){value in                   let offset = value + ( UIScreen.main.bounds.height / 2.2)                   if offset < 80 {                     if offset > 0 {                       let opactity_value = (80 - opactity) / 80                       self.opacity = Double(opactity_value)                       return                     }                     self.opacity = 1                   }                   else {                     self.opacity = 0                   }               }             }           }