Property wrappers are not yet supported on local properties error message

Using Swift
1

I am new to swift and coped-pasted some code but it does not compile and I don't understand why and can't figure out why.

// ObservableObject that limits text fields to numbers (digits) only            
class NumbersOnly: ObservableObject {                                           
    @Published var value = "" {                                                 
        didSet {                                                                
            let filtered = value.filter { $0.isNumber }                         
                                                                                
            if value != filtered {                                              
                value = filtered                                                
            }                                                                   
        }                                                                       
    }                                                                           
}

The code is on github here: DeliveryBox/MobileApp/DeliveryBox_iOS/DeliveryBox_iOS/ContentView.swift at main · RobertPHeller/DeliveryBox · GitHub

I have an "old" MacBook (2013 vintage, running MacOS 10.15.8), with XCode 12.4 (Apple Swift version 5.3.2 (swiftlang-1200.0.45 clang-1200.0.32.28). (I know this is old, but it is what I have and I really can't afford to buy a new Mac, esp. since I am not really a mac user.)

2

Hello, @RobertPHeller

You should at least show the offending piece of code, by enclosing it between a pair of three backtick characters (```):

```
Paste Code Here
```

If you do that, the code will appear like this: :slight_smile:

@main
enum Driver {
    static func main() async throws {
        let f = f_or_g (true)
        print (f ())
        // Error: Missing argument for parameter #1 in call
    }
}

func f () -> Int {
    return 2
}

func g () -> Int {
    return 3
}

func g (_ u: Int) -> Int {
    return 5
}


#if true
    // Does not compile
    func f_or_g (_ u: Bool) -> (Int) -> Int {
        return u ? f : g
        // Error: Cannot convert value of type '@Sendable () -> Int' to specified type '(Int) -> Int'
    }
#elseif true
    // Compiles
    func f_or_g (_ u: Bool) -> () -> Int {
        if u {
            return f
        }
        else {
            return g
        }
    }
#else
    // Compiles
    func f_or_g (_ u: Bool) -> @Sendable () -> Int {
        return u ? f : g
    }
#endif
3

OK, I pasted it. (I don't really like forums -- the editers are strange and hard (for me) to use. I did include a link to the file on github.

4

OK, I moved the Observer code to a separate file and error went away. I also appears the there is something fishy with the IDE. Errors show up in the IDE's editor, but the errors go away when I explicitly Build the project.

5

What kind of errors show up?

6

The errors are supurious. I think the IDE is getting confused because I am
using an external editor and it generating errors on partially re-loaded
files. I am not ignoring any errors that automagically popup when the file
gets modified. I just explicitly select Build or Run from the Product menu.

7

If your IDE is flaky, another source of compiler truth for small programs from old computers is the "godbolt" compiler explorer, which supports Swift both modern and ancient:

https://godbolt.org

8

Building the project is your source of truth. If errors disappear after building, then it is not a real problem in code.

1 Like