匕首：如果我每次都*想要*一个新实例怎么办？ [英] Dagger: What if I *WANT* a new instance every time?

问题描述

有趣的是，很难找到答案。

Interesting how difficult this answer is to find.

我已经使用Dagger-Android已有一段时间了，并设置了我的整个依赖关系图。我正在使用范围，限定词以及所有这些好东西。我已经不再是Dagger的新手了，不过可以说我已经在我的Android设置中以非常标准的方式使用它了，一切都进行得很好。

I've been using Dagger - Android for a while now and have my entire dependency graph set up. I'm using scopes, qualifiers, all that good stuff. I'm not a Dagger newbie anymore, but suffice to say I've been using it in a pretty standard way in my Android setup and everything has been going great.

第一次，我意识到我想手动地在自己的图形中请求某个类的新实例，并且我希望每次都是新实例。

For the first time, I'm realizing that I'd like to request new instances of a certain class in my graph myself, manually, and I want it to be a new instance every time.

执行此操作的最佳方法是什么？我想知道是否有一种方法可以利用非@ Singleton /非作用域提供程序并自己调用某种 create（）方法，或者是否最好创建自己创建一个工厂，并让该工厂成为单例/作用域实例，并在需要时使用我的工厂来获取新实例？ [我应该提一下，此类肯定没有具有空的构造函数，因此需要在注入图中定义的其他类的注入实例。

What's the best way to go about doing that? I'm wondering if there's a way to leverage a non-@Singleton/non-scoped provider and call some sort of create() method myself, or if it's best to create a factory myself and make that factory a singleton/scoped instance and use my factory to get the new instance(s) when I need them? [I should mention this class will definitely not have an empty constructor so will need injected instances of other classes defined in my injection graph.]

（此外，如果答案是在Android上下文中，这可能会最大程度地帮助您；例如，我在ViewModel中，并且需要在我的一个模块中定义的某个类的新实例。）

(Also, it would probably help the most if answers were in the context of Android; i.e. I'm in, say, a ViewModel and need a new instance of some class defined in one of my Modules.)

推荐答案

只要您不限制依赖项，Dagger就会为您提供一个新实例。

Dagger will provide you a new instance as long as you don't scope the dependency.

要手动获取依赖项的新实例，可以注入它的 Provider 并使用其 get（）方法，每次调用它都会为您提供一个新实例。

To get a new instance of a dependency manually, you can inject Provider of it instead and use its get() method, it'll give you a new instance every time you call it.

模块部分并没有真正改变：

Module part doesn't really change:

@Module
class AppModule {

    @Provides
    fun provideSomeObject(): SomeObject = SomeObject()
}

在您的班上

class SomeClass {
    // We don't inject the object anymore
    // @Inject lateinit var myObject : SomeObject

    // We'll inject it's provider
    @Inject lateinit var myObject : Provider<SomeObject>

    fun someMethod(){
        // Here, instance1 and instance2 are NOT same objects
        val instance1 = myObject.get()
        val instance2 = myObject.get()
    }
}

您可以阅读更多此处。

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