如何检查对象是否存在于 NSMutableArray 的某个索引处? [英] How do I check if an object exists at a certain index of an NSMutableArray?

问题描述

例如，我如何验证索引 3 处是否有项目?

For instance, how could I verify if there is an item at the index 3?

NSArray 中的对象是从类Animal"实例化的.

The objects in the NSArray are instantiated from the class "Animal."

推荐答案

好吧，既然 NSMutableArray 必须保存非 nil 对象，只要数组足够大，你就知道有 东西在索引i:

Well, since NSMutableArray has to hold non-nil objects, as long as the array is big enough, you know there's something at index i:

if ([myArray count] > 3) {
    id myObj = [myArray objectAtIndex:3];
    ...
}

如果您需要检查其他内容，例如确保它没有对 NSNull 单例的引用，您可以检查

If you needed to check something elsek, like say make sure it didn't have a reference to the NSNull singleton, you could then check

if (myObj != [NSNull null]) ...

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