SwiftUI：如何为环境对象ViewModel的属性创建Binding？

你需要把环境中ViewModel的showDetails属性以Binding形式传递给DetailsButton，有两种简洁的实现方式，适配iOS 17/macOS 14的新Observation框架：

方式一：用@Bindable包装环境ViewModel（推荐） #

通过@Bindable修饰环境中的Observable对象，就能像使用@State一样用$语法直接生成Binding，写法最简洁：

完整代码 #

@Observable class ViewModel {
    var showDetails: Bool
    // 添加默认初始化方法，方便实例化
    init(showDetails: Bool = false) {
        self.showDetails = showDetails
    }
}

struct TestApp: App {
    @State var vm = ViewModel()
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(vm)
        }
    }
}

struct ContentView: View {
    // 用@Bindable和@Environment组合，直接生成可绑定的ViewModel实例
    @Bindable @Environment(ViewModel.self) private var vm
    
    var body: some View {
        VStack {
            // 直接传递$vm.showDetails，和原示例的用法一致
            DetailsButton(showDetails: $vm.showDetails)
            if vm.showDetails {
                Text("This is my message!")
            }
        }
    }
}

struct DetailsButton: View {
    @Binding var showDetails: Bool
    var body: some View {
        Button("\(showDetails ? "Hide" : "Show") Details") {
            showDetails.toggle()
        }
    }
}

方式二：手动构造Binding #

如果需要自定义属性的读取/赋值逻辑，可以手动通过Binding(get:set:)构造器生成绑定：

完整代码 #

@Observable class ViewModel {
    var showDetails: Bool
    init(showDetails: Bool = false) {
        self.showDetails = showDetails
    }
}

struct TestApp: App {
    @State var vm = ViewModel()
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(vm)
        }
    }
}

struct ContentView: View {
    @Environment(ViewModel.self) private var vm
    
    var body: some View {
        VStack {
            DetailsButton(
                showDetails: Binding(
                    get: { vm.showDetails },
                    set: { vm.showDetails = $0 }
                )
            )
            if vm.showDetails {
                Text("This is my message!")
            }
        }
    }
}

struct DetailsButton: View {
    @Binding var showDetails: Bool
    var body: some View {
        Button("\(showDetails ? "Hide" : "Show") Details") {
            showDetails.toggle()
        }
    }
}

两种方式都能实现和原示例完全一致的功能，推荐使用方式一，语法更符合SwiftUI的设计习惯。

内容的提问来源于stack exchange，提问作者Anton