xcode 无法预览新的 SwiftUI 项目

Question

I'm running Catalina 10.15.7, and XCode 12.3.

New Project -> Single View App -> provide name (all alpha, no breaks or punctuation). Project launches. Without making any changes whatever, I click on Resume Preview, and get a message: "Cannot preview in this file: Failed to launch

The code in ContentView.swift is standard, and confirmed in various videos etc.:

import SwiftUI

struct ContentView: View {
    var body: some View {
        Text("Hello, world!")
            .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

As I launched XCode, I was asked to upgrade certain unspecified components, which I did.

But no joy. What's the solution?

Answer 1

The answer was obviousish once found, which of course happened right after asking.

I had mistakenly created a project for macos, and I wanted a project for iOS. I'm pretty sure that most of you figured that out...