为什么设置类变量NSArray要求我使用访问器方法？

Question

I'm using a NSFetchRequest to create a section in a UITableView based on objects stored in Core Data.

In the viewDidLoad I do the fetch request and set the returned array of NSManagedObjects to a class variable NSArray *allEvents. I was setting the array returned from the fetch request like so:

    allEvents = [context executeFetchRequest:eventFetchRequest error:&error];

I was getting a EXEC_BAD_ACCESS error when I tried calling [allEvents count] in my numberOfRowsInSection later on.

I managed to fix the problem by setting the array from the fetch request by adding self to the above line of code:

    self.allEvents = [context executeFetchRequest:eventFetchRequest error:&error];

Can anyone explain why this worked? I've run into similar situations and would love to know what's going on.

Thanks.

Answer 1

对象上的“ allEvents”属性很可能是保留属性，因此在第一种情况下，该数组没有保留，在您访问该数组时已被释放。