Struct 'State' cannot be used as an attribute

Question

I have the following code in a ContentView.swift file:

struct ContentView: View {
    @State private var selectedSpeed: Int = 1
    
    var body: some View {
        Text("Hello World")
    }
}

I have simplified it for the sake of readability. I know that selectedSpeed is not being used.

In the line where selectedSpeed is declared, I'm getting the following error: Struct 'State' cannot be used as an attribute

Interestingly, pasting the exact same code in a Playground builds successfully. I'm on Xcode 12.1. I've tried the combo of nuking derived data and re-opening Xcode but the error persists. Any ideas what is wrong here?

Answer 1

It turned out that I had a struct called State in my project and that caused the problem.

TL;DR: Never call any of your structs, and potentially classes, State if you're planning on using SwiftUI. I would expand it to not name any of your classes or structs with something that clashes with a property wrapper.

That also explains why everything was ok in the Playground.

The Report navigator was actually giving me the hint

Answer 2

The name State is not protected and as per your reply/answer you have State declared elsewhere, either in your own app or inside a dependency that you might be importing into that file.

You can tell the compiler what symbol to use by explicitly setting the correct "Namespace".

For example:

struct ContentView: View {
    @SwiftUI.State private var selectedSpeed: Int = 1
    
    var body: some View {
        Text("Hello World")
    }
}