SwiftUI - 在预览中模拟 @EnvironmentObject 数据 [英] SwiftUI - Mocking @EnvironmentObject data in preview

问题描述

我有这个代码:

struct WelcomeView: View {
    @EnvironmentObject var userService: UserService
    var body: some View {
        Text(userService.user.username)
    }
}

struct WelcomeView_Previews: PreviewProvider {
    static var previews: some View {
        WelcomeView().environmentObject(UserService())
    }
}

我想要实现的所有 UI 组件都使用模拟数据.我需要以某种方式告诉我，在预览中，我希望将 Text(userService.user.username) 视为 Text("Alex") 例如.我怎样才能让它工作?我需要在哪里初始化我的 user.username 以及将这个模拟放在哪里.我只想将 user 对象用于我的所有视图.我只是跳过了这个例子.

What I want to achieve that all my UI components use mock data. I need to tell somehow that in preview I would like to see Text(userService.user.username) as Text("Alex") for example. How can I make it work? Where I need to initialise my user.username and where to put this mock. I just want to use the user object for all my views. I just skipped them for this example.

推荐答案

假设 UserService 已经正确设计使用依赖注入，它可以使用以下方法对生产代码进行任何显式更改

Assuming the UserService has correctly designed using dependency injection, it can be used the following approach with any explicit changes in production code

struct WelcomeView_Previews: PreviewProvider {
    static var previews: some View {
        let userService = UserService()
        userService.user = User(username: "Alex", email: "[e-mail]") // << any predefined set up here
        // any more parameters set up here

        return WelcomeView().environmentObject(userService)
    }
}

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