SwiftUI 可选文本字段 [英] SwiftUI Optional TextField

问题描述

SwiftUI 文本字段可以与可选绑定一起使用吗?目前此代码:

Can SwiftUI Text Fields work with optional Bindings? Currently this code:

struct SOTestView : View {
    @State var test: String? = "Test"

    var body: some View {
        TextField($test)
    }
}

产生以下错误:

无法转换类型绑定<"的值String?>' 到预期的参数类型 'Binding<;字符串>'

Cannot convert value of type 'Binding< String?>' to expected argument type 'Binding< String>'

有什么办法可以解决这个问题吗?在数据模型中使用 Optionals 是一种非常常见的模式 - 事实上它是 Core Data 中的默认值，所以 SwiftUI 不支持它们似乎很奇怪

Is there any way around this? Using Optionals in data models is a very common pattern - in fact it's the default in Core Data so it seems strange that SwiftUI wouldn't support them

推荐答案

最终 API 不允许这样做 - 但有一个非常简单且通用的解决方法:

Ultimately the API doesn't allow this - but there is a very simple and versatile workaround:

extension Optional where Wrapped == String {
    var _bound: String? {
        get {
            return self
        }
        set {
            self = newValue
        }
    }
    public var bound: String {
        get {
            return _bound ?? ""
        }
        set {
            _bound = newValue.isEmpty ? nil : newValue
        }
    }
}

这允许您在使其与绑定兼容的同时保留可选项:

This allows you to keep the optional while making it compatible with Bindings:

TextField($test.bound)

这篇关于SwiftUI 可选文本字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！