什么是更好的方式添加Observer / removeObserver与NSNotificationCenter？ [英] What's the better way to addObserver/removeObserver with NSNotificationCenter?

问题描述

我习惯于 viewDidLoad：和 removeObserver 中的 addObserver > dealloc：。代码：

I used to addObserver in viewDidLoad: and removeObserver in dealloc:. Code:

- (void)viewDidLoad
{
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(refreshData)
                                                 name:AnyNotification
                                               object:nil];
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:AnyNotification
                                                  object:nil];
}

但根据一些文章说，在中的 viewDidAppear：和 removeObserver 视图dDisappear： code>。代码：

But according to some articles said, it's better to addObserver in viewDidAppear: and removeObserver in viewDidDisappear:. Code:

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(refreshData)
                                                 name:AnyNotification
                                               object:nil];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:AnyNotification
                                                  object:nil];
}

那么，addObserver / removeObserver的更好的方法是什么？

So, what's the better way to addObserver/removeObserver?

推荐答案

这取决于你的场景，通常最好的办法是在 viewDidLoad 在 dealloc 和 viewDidUnload 中，但是有一些情况下，你有相同的方法在不同的类，使用通知只调用当前屏幕的方法，则必须在 viewWillAppear 中添加观察者，并在 viewWillDisappear 或 viewDidAppear / viewDidDisappear

this depends on your scenario, usually the best approach is to add in viewDidLoad and remove in dealloc and in viewDidUnload, but there are some cases when you have same method in different classes like UI effects and want to call only current screen's method using notification, then you will have to add the observer in viewWillAppear and remove it in viewWillDisappear or viewDidAppear/viewDidDisappear

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