ERROR on XCODE: Cannot use instance member 'selectedWateredDate' within property initializer; property initializers run before 'self' is available

stackoverflow community.

This is my first post/question on here.
Newbie here. I’m trying to make a plantApp using SwiftUI, but currently running into an error.

I’m trying to figure out why I keep getting the following error
"Cannot use instance member ‘selectedWateredDate’ within property initializer; property initializers run before ‘self’ is available" for my "dateInterval" variable.

@State private var selectedWateredDate = Date()
@State private var waterMeAgainIn: Date = Date().addingTimeInterval(7 * 86400)


let dateInterval = DateInterval(start: selectedWateredDate, end: waterMeAgainIn)

>Solution :

Change the let property to a computed variable.

var dateInterval : DateInterval { DateInterval(start: selectedWateredDate, end: waterMeAgainIn)}