@State variable $ sign usage : <p>Learning SwiftUI and having some difficulty in understanding @State. For example in the code below, why don't we use State variable (that is with $ sign) with if statement? Why only as Toggle argument? How do we differentiate both the states?</p>

<pre><code>import SwiftUI

struct ContentView: View {
    @State private var isFrown = true
    var body: some View {

       VStack
        {
        Text ("Check toggle state")
        Toggle(isOn: $isFrown) {
                Text("")
                    .padding()
            if isFrown {          //why not $isFrown here
            Text("🤨")
            }
            else {
            Text("😃")
            }

        }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
</code></pre>
