ios检查nsarray == null

问题描述

我收到了来自 JSON 的回复，并且工作正常，但我需要检查一些 null 值，

I'm receiving some response from JSON, and is working fine, but I need to check for some null values,

我找到了不同的答案，但似乎仍然没有工作，

I have found different answers but seems is not working still,

NSArray *productIdList = [packItemDictionary objectForKey:@"ProductIdList"];

我试过

if ( !productIdList.count )  //which breaks the app,

if ( productIdList == [NSNull null] )  // warning: comparison of distinct pointer types (NSArray and NSNull)

那么发生了什么？如何解决这个问题并在我的数组中检查 null ？

So what is happening? How to fix this and check for null in my array?

谢谢！

推荐答案

使用演员阵容消除警告：

Eliminate the warning using a cast:

if (productIdList == (id)[NSNull null])

如果 productIdList 实际上是 [NSNull null] ，然后执行 productIdList.count 会引发异常，因为 NSNull 无法理解计数消息。

If productIdList is in fact [NSNull null], then doing productIdList.count will raise an exception because NSNull does not understand the count message.

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