iOS：使用app委托来容纳全局变量-iOS:Usingtheappdelegatetohouseglobalvariables

7  

The real solution to your question isn't to replace one form of global state with another (i.e. singletons).

你问题的真正解决方案不是将一种形式的全球状态替换为另一种形式(即单身人士)。

What you should be doing is putting state within "model" classes that are instantiated inside your app delegate, and then passing them down to the parts of your application that need them (e.g. view controllers), thereby eliminating your global state problem entirely.

您应该做的是将状态放在应用程序委托中实例化的“模型”类中,然后将它们传递给需要它们的应用程序部分(例如视图控制器),从而完全消除您的全局状态问题。

3  

Its generally not a good practice to load up your AppDelegate as a container for app-wide variables in this way. It can quickly get unwieldy.

以这种方式将AppDelegate作为应用程序范围变量的容器加载通常不是一个好习惯。它很快就会变得笨拙。

A common practice is to define some singleton objects, as follows:

通常的做法是定义一些单例对象,如下所示:

+ (instancetype)shared
{
    static dispatch_once_t onceToken;
    static MyServiceClient* instance;

    dispatch_once(&onceToken, ^  //Use GCD to make a singleton with thread-safety
    {
        instance = [[self alloc] init];
    });
    return instance;
}

You can then provide these objects as parameters to your classes that require them as collaborators.

然后,您可以将这些对象作为参数提供给需要它们作为协作者的类。

Use Dependency Injection

使用依赖注入

Note though that singleton can be considered an anti-pattern. If you inject these singletons into classes that require them its not too bad, however it's definitely not recommend to hard-wire them (unfortunately, also a common practice), as this promotes too-tight coupling, cohesion and requires complicated swizzling in order perform unit tests.

请注意,单例可以被视为反模式。如果你将这些单体注入需要它们的类别并不太糟糕,但绝对不建议硬连线(不幸的是,这也是一种常见的做法),因为这会促进过于紧密的耦合,凝聚力并需要复杂的调配才能执行单元测试。

Another approach is to use dependency injection, in which case the objects need not even be singletons, in most cases. You can instantiate an object-graph of collaborating components for a given use-case that will come and go as needed. This has the benefit of using less memory on resource constrained devices.

另一种方法是使用依赖注入,在这种情况下,在大多数情况下,对象甚至不需要是单例。您可以根据需要实例化给定用例的协作组件的对象图。这样做的好处是可以在资源受限的设备上使用更少的内存。

Its a common misconception that you need a library to use dependency injection. You don't. It can help though. I created a dependency injection container called Typhoon.

它是一个常见的误解,你需要一个库来使用依赖注入。你没有。它可以帮助。我创建了一个名为Typhoon的依赖注入容器。

Notifications

Another way of achieving loose collaboration between classes is to use notifications.

在类之间实现松散协作的另一种方法是使用通知。