firstOnAppear View Modifier

firstOnAppear.swift

struct FirstOnAppearModifier: ViewModifier {
    @State private var hasPerformedAction = false
    let action: (() -> Void)?
    
    func body(content: Content) -> some View {
        content
            .onAppear {
                if !hasPerformedAction {
                    hasPerformedAction = true
                    action?()
                }
            }
    }
}

extension View {
    /// Same as `onAppear(perform:)` except the optional `action` only triggers the _first_ time the view appears, instead of _every_tiime.
    func firstOnAppear(performOnce action: (() -> Void)? = nil) -> some View {
        modifier(FirstOnAppearModifier(action: action))
    }
}

/*
// Example Usages
struct View1: View {
    var body: some View {
        Text("View 1")
            .firstOnAppear {
                print("View 1 appears")
            }
    }
}

struct View2: View {
    var body: some View {
        Text("View 2!")
            .onAppear {
                print("View 2 appears")
            }
    }
}
*/