SwiftUI How to instantiate PreviewProvider when View requires @Binding in initializer

Question

With SwiftUI (Xcode 11.1), I\'ve got some Views set up with 2-way bindings (using @Binding). Two-way updating works great.

However, how can I insta

Answer 1

If you only need a constant value, use .constant(VALUE):

struct YourView_Previews: PreviewProvider {

    static var previews: some View {
        YourView(yourBindingVar: .constant(true))
    }

}

If you need a value that can be changed in the live preview, I like to use this helper class:

struct BindingProvider: View {

    @State private var state: StateT
    private var content: (_ binding: Binding) -> Content

    init(_ initialState: StateT, @ViewBuilder content: @escaping (_ binding: Binding) -> Content) {
        self.content = content
        self._state = State(initialValue: initialState)
    }

    var body: some View {
        self.content($state)
    }
}

Use it like so:

struct YourView_Previews: PreviewProvider {

    static var previews: some View {
        BindingProvider(false) { binding in
            YourView(yourBindingVar: binding)
        }
    }

}

This allows you to test changing the binding in the live preview.