SwiftUI - alternative to if let with a conditional closure

For such cases I prefer the following approach

struct PersonView: View {

    @State private var age: Int? = 0

    var body: some View {
        VStack {
            Text("Just a test")
            AgeText
        }
    }

    private var AgeText: some View {
        if let age = self.age, age > 0 {
            return Text("Display Age: \(age)")
        } else {
            return Text("Age must be greater than 0!")
        }
    }
}

You are trying to do two check on the value of age: first you are making sure it is not nil and then checking that it is greater than 0. You can use map to get rid of potential nil and then a ternary operator to conditionally change the text displayed:

var body: some View {
    VStack {
        Text("Just a test")
        age.map { Text( $0 > 0 ? "Display Age: \($0)" : "Age must be greater than 0!") }
    }
}

Swift 5.3 (Xcode 12)

Now you can use conditional binding right in the view builder:

if let age = age {
    if age > 0 {
        Text("Display Age: \(age)")
    } else {
        Text("Age must be greater than 0!")
    }
} else {
    Text("Age not found")
}

---

Refactor (Workes in older Swifts too)

You can refactor your code to something more basic like using a function:

var body: some View {
    VStack {
        Text("Just a test")
        Text(text(age: age)) // Using the function
    }
}

func text(age: Int?) -> String { // Defining the function
    guard let age = age else { return "Age not found" }
    if age > 0 { return "Display Age: \(age)" }
    else { return "Age must be greater than 0!" }
}

In general, use functions where you need to cleanup your code. I hope future versions of Swift will support this directly as we expect.