iPhone - 测试是否存在通知 [英] iPhone - testing if a notification exists

问题描述

在某个代码中，我可以添加类似

At some point in a code one may add something like

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(doSomething) name:@"Hello" object:nil];   

如何测试此通知是否已在队列中处于活动状态或已被删除，以防止添加重复？

How do I test if this notification is already active on the queue or has been removed, to prevent adding a duplicate?

谢谢。

推荐答案

如果你的意思是测试对于你是否已经注册为通知的观察员，我认为除了发布通知并看到你收到回调（可能带来灾难性后果）之外，还有一种简单的方法。

If you mean "testing for whether you've already registered as an observer for the notification", I don't think there's an easy way apart from posting the notification and seeing you get a callback (with possibly disastrous effects).

如果存在双重添加的危险，我通常会使用 [[NSNotificationCenter defaultCenter] removeObserver：self name：foo object：bar] 添加。

If there's a danger of a double-add, I usually use [[NSNotificationCenter defaultCenter] removeObserver:self name:foo object:bar] before the add.

在队列中不会注册通知。

Registering for notifications does not happen on a queue.

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