如何实现三个同类型EnvironmentObject实例？SwiftUI设计方案咨询

SwiftUI中同类型的EnvironmentObject确实只能在环境中存在一个，直接添加多个同类型实例会导致后续实例覆盖前面的，以下是几种可行的解决方案：

创建一个容器类封装所有PredictService实例，将容器作为单个EnvironmentObject注入环境，子视图通过容器访问各个独立服务。

示例代码：

// 定义容器类
class PredictServicesContainer: ObservableObject {
    let service1 = PredictService()
    let service2 = PredictService()
    let service3 = PredictService()
}

// 在App中注入容器
struct MyAPP: App {
    @StateObject private var servicesContainer = PredictServicesContainer()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(servicesContainer)
        }
    }
}

// 在视图中使用
struct ContentView: View {
    @EnvironmentObject private var servicesContainer: PredictServicesContainer

    var body: some View {
        VStack {
            RepeatView(predictService: servicesContainer.service1)
            RepeatView(predictService: servicesContainer.service2)
            RepeatView(predictService: servicesContainer.service3)
        }
    }
}

// 重复子视图
struct RepeatView: View {
    let predictService: PredictService
    var body: some View {
        // 视图内容
    }
}

通过自定义环境键，为每个PredictService实例分配唯一标识，实现单独注入和获取，不依赖类型区分。

示例代码：

// 自定义三个环境键
private struct PredictService1Key: EnvironmentKey {
    static let defaultValue: PredictService = PredictService()
}

private struct PredictService2Key: EnvironmentKey {
    static let defaultValue: PredictService = PredictService()
}

private struct PredictService3Key: EnvironmentKey {
    static let defaultValue: PredictService = PredictService()
}

// 扩展EnvironmentValues添加访问器
extension EnvironmentValues {
    var predictService1: PredictService {
        get { self[PredictService1Key.self] }
        set { self[PredictService1Key.self] = newValue }
    }

    var predictService2: PredictService {
        get { self[PredictService2Key.self] }
        set { self[PredictService2Key.self] = newValue }
    }

    var predictService3: PredictService {
        get { self[PredictService3Key.self] }
        set { self[PredictService3Key.self] = newValue }
    }
}

// 在App中注入
struct MyAPP: App {
    @StateObject private var service1 = PredictService()
    @StateObject private var service2 = PredictService()
    @StateObject private var service3 = PredictService()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(\.predictService1, service1)
                .environment(\.predictService2, service2)
                .environment(\.predictService3, service3)
        }
    }
}

// 在视图中使用
struct ContentView: View {
    @Environment(\.predictService1) private var service1
    @Environment(\.predictService2) private var service2
    @Environment(\.predictService3) private var service3

    var body: some View {
        VStack {
            RepeatView(predictService: service1)
            RepeatView(predictService: service2)
            RepeatView(predictService: service3)
        }
    }
}

如果三个重复视图直接在ContentView中声明，可直接将服务实例传递给子视图，无需依赖环境，实现简单直观：

struct MyAPP: App {
    @StateObject private var service1 = PredictService()
    @StateObject private var service2 = PredictService()
    @StateObject private var service3 = PredictService()

    var body: some Scene {
        WindowGroup {
            ContentView(
                service1: service1,
                service2: service2,
                service3: service3
            )
        }
    }
}

struct ContentView: View {
    let service1: PredictService
    let service2: PredictService
    let service3: PredictService

    var body: some View {
        VStack {
            RepeatView(predictService: service1)
            RepeatView(predictService: service2)
            RepeatView(predictService: service3)
        }
    }
}

内容的提问来源于stack exchange，提问作者erotsppa