Unity / Caliburn Micro，具有多个参数的注射构造器 [英] Unity/Caliburn Micro, Injection Constructor with multiple parameters

问题描述

我目前正在尝试学习如何使用Unity和Caliburn Micro实现MVVM。在其他地方寻求帮助后，我仍然不确定如何正确设置构造函数注入。我不知道是否由于我对MVVM的专业知识不足或其他原因而无法正常工作。

I am currently trying to learn how to implement MVVM using Unity and Caliburn Micro. After looking around for help elsewhere I am still unsure about how to set up the Constructor Injection properly. I don't know if this is not working due to my lack of expertise in MVVM or something else.

我的问题是我想将两个IScreen对象传递给我主窗口（外壳）在用户单击按钮之间可以导航的类。这是MainWindowViewModel类中构造函数的代码：

My problem is I want to pass in two IScreen Objects into my main window(shell) Class that can be navigated between when the user clicks on a button. Here is the code for the constructor in my MainWindowViewModel class:

private IScreen campaignViewModel, stringsViewModel;
public MainWindowViewModel(IScreen campaignViewModel, IScreen stringsViewModel)
{
    this.campaignViewModel = campaignViewModel;
    this.stringsViewModel = stringsViewModel;
    ActiveItem = this.campaignViewModel;
}

这是我在Bootstrapper（Unity）类中使用的代码：

This is the code I am using in my Bootstrapper(Unity) class:

    private static IUnityContainer BuildContainer()
    {
        IUnityContainer result = new UnityContainer();
        result
            .RegisterInstance(result)
            .RegisterInstance<IWindowManager>(new WindowManager())
            .RegisterInstance<IEventAggregator>(new EventAggregator());

        result
            .RegisterType<IScreen, CampaignsViewModel>()
            .RegisterType<IScreen, StringsViewModel>()
            .RegisterType<MainWindowViewModel>(new InjectionConstructor(typeof(IScreen), typeof(IScreen)));

        return result;
    }

    protected override object GetInstance(Type service, string key)
    {
        var result = unity.Resolve(service, key);

        if (result == null)
            throw new Exception(string.Format("Could not locate any instance of contract {0}", service));
        return result;
    }

在运行MainWindowViewModel时，它会收到两个StringsViewModel实例。尽管如果要在语句中放入键：

When this runs the MainWindowViewModel receives two instances of StringsViewModel. Although if I were to put a key into the statement:

result.RegisterType<IScreen, StringsViewModel>("StringsView");

然后，它在CampaignsViewModel的两个实例中传递。我不知道如何指定我要让它传递给CampaignViewModel和StringsViewModel的一个实例的InjectionConstructor。我感觉它可能与GetInstance方法有关，但是我不确定。

Then it passes in two instances of CampaignsViewModel. I don't know how to specify to the InjectionConstructor that I want it to pass in one instance of CampaignViewModel and StringsViewModel. I have a feeling it may have something to do with the GetInstance method, but I am unsure.

任何帮助将不胜感激！

谢谢。

推荐答案

在构造函数中，您两次定义了相同的接口。

In your constructor you define the same interface twice.

DI框架如何知道哪个？答案：不能。

How will the DI framework know which is which?? Answer: it can't.

因此，请不要使用2个接口：

So instead of this use 2 interfaces:

 public MainWindowViewModel(ICampaignScreen campaignViewModel, IStringsScreen stringsViewModel)

您可以使这两个继承自IScreen：

You can make both of these inherit from IScreen:

 public interface ICampaignScreen : IScreen

也不需要向IScreen添加任何内容-它们只是为框架提供了一种区分它们的方法。

and neither need add anything to IScreen - they simply provide a means for the Framework to differentiate between them.

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