swift - SwiftUI 中带有自定义绑定(bind)的可选扩展

Question

有没有办法为 Optional 值创建一个扩展，这样我们就不需要单独创建自定义绑定(bind)。

class ViewModel: ObservableObject {
    @Published var text: String?
}

struct ContentView: View {
    @ObservedObject var model: ViewModel
    
    var body: some View {
        let binding = Binding(
            get: { self.model.text ?? "" },
            set: { self.model.text = $0 }
        )
        
        return VStack {
            TextField("Text", text: binding)
        }
    }
}

我正在考虑做这样的事情

extension Optional where Wrapped == String {
    func optionalBinding() -> Binding<String> {
        return Binding(get: {
            self ?? ""
        }, set: { newValue in
            self = newValue
        })
    }
}

对此有什么建议吗？

Answer 1

您可以尝试扩展 Binding 而不是 Optional:

extension Binding where Value == String? {
    var optionalBinding: Binding<String> {
        .init(
            get: {
                self.wrappedValue ?? ""
            }, set: {
                self.wrappedValue = $0
            }
        )
    }
}

然后像这样使用它:

class ViewModel: ObservableObject {
    @Published var text: String?
}

struct ContentView: View {
    @ObservedObject var model = ViewModel()

    var body: some View {
        VStack {
            TextField("Text", text: $model.text.optionalBinding)
            Text(String(describing: model.text))
        }
    }
}