在匕首1.x的单身 [英] Singletons in Dagger 1.x

问题描述

在使用匕首，我发现，我得到一个单身的多个实例时，我把它注射的地方，我需要它。我已经诠释了类和提供方法 @Singleton 。谁能想到为什么会这样？

编辑：

如果有帮助，我都遵循相同的结构，我的应用程序在匕首的GitHub上的示例应用程序（<一href="https://github.com/square/dagger/tree/master/examples/android-activity-graphs">https://github.com/square/dagger/tree/master/examples/android-activity-graphs).我试图让辛格尔顿在基本活动和一对夫妇使用提供第三方类 @Provides 在自定义的应用程序类。是不是因为我在每个活动到原来的对象图加荷兰国际集团的模块？

（PS：我是新来的匕首和DI一般，所以我会很感激，如果你能提供一个解释，这样我可以学习谢谢）

解决方案

@Singleton ，在匕首1.x中，行为不同于你的想象。在 @Singleton Javadoc中的JSR-330规范的定义是每一个图形，这是怎样的匕首间$ P $点吧。

所以，如果你有一些被标记为 @Singleton ，它物化在应用程序图（而不是更短的寿命图），然后你每个应用程序的一个实例。

如果你有一个项目注释 @Singleton 这是在你用它来配置活动图（即，从图中由指定的部分获得的模块在加号（）操作使用的模块），那么你会得到一个每活性图。

如果你需要的东西是一次每个应用程序，你需要确保它被创建为应用程序图的一部分。您可以通过以下两种方法之一做到这一点。无论是从您的应用程序模块（S），明确规定将其与@Provides方法，也可以将其列为在@Module在应用程序模块中的一个类（注入= ...）。

（如果你不使用 @Singleton 标记它比你会得到每注射部位之一。）

所以记住，通过加（）创建的被视为一个指向它从中衍生出图中的单独的图形的图形，并把它封装，可以在它访问的实例，但是不一样的曲线图。

注 - 匕首2.X提高了这一点，并支持自定义作用域的注解，虽然该机制是相似的，每个范围标注一个图（部分），与更广泛/窄寿命曲线之间的父/子关系的

When using Dagger, I found that I'm getting multiple instances of a singleton when I inject it wherever I need it. I've annotated the class and the provides method with @Singleton. Can anyone think of why this is happening?

Edit:

If it helps, I have followed the same structure for my app as the sample application in Dagger's GitHub (https://github.com/square/dagger/tree/master/examples/android-activity-graphs). I'm trying to get the Singleton in the base activity and a couple of third party classes provided using @Provides at the custom Application class. Is it because I'm plus-ing modules at each activity to the original object graph?

(PS : I'm new to Dagger and DI in general, so I'll be grateful if you could provide an explanation so that I may learn. Thanks.)

解决方案

@Singleton, in Dagger 1.x, acts differently than you might think. The JSR-330 spec definition in the @Singleton javadoc is "one per graph" and that is how Dagger interprets it.

So if you have something that is marked as @Singleton, and it is materialized in your application graph (as opposed to a shorter-lifetime graph), then you get one instance per application.

If you have an item annotated @Singleton that's in the modules you use to configure your activity graph (i.e., that is obtained from the part of a graph specified by a module used in the plus() operation) then you will get one-per-activity-graph.

If you need something to be once-per-application, you need to make sure it gets created as a part of the application graph. You can do this in one of two ways. Either explicitly provide it with an @Provides method from your application module(s), or you can list it as a one of the classes in @Module(injects=...) in an application module.

(If you do not mark it with @Singleton than you will get one per injection site.)

So remember, the graph created by plus() is seen as a separate graph that points to the graph from which it was spawned, and wraps it, can access instances within it, but is not the same graph.

Note - Dagger 2.x improves this, and supports custom scoping annotations, though the mechanism is similar, with one graph (component) per scope annotation, with a parent/child relationship between graphs of wider/narrower lifetimes

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