iphone：tableview没有数据时objectAtIndex崩溃

Question

i have the following code

[[categories objectAtIndex:row]objectForKey:@"name"];

where categories is nsmutablearray .. it is in a tableview but if categories have 0 rows (not null) it gives exception and crash .. the exception is

Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (0) beyond bounds (0)'

so how can i load the table without throw exception

Answer 1

An empty array will throw this exception if you try to access anything because there is never an object at any index if the array is empty. It's like me not owning a car, but you asking to borrow my car.. you cant borrow my car if I dont have one (then me throwing an exception fist at you for making me realize I'm too poor to own a car) ! =)

Do this instead:

if ([categories count]) {
    [[categories objectAtIndex:row]objectForKey:@"name"];
    ....
}

---

Edit:

Actually, you would probably want to change that if statement to make sure it has at least row + 1 number of objects.

if (([categories count] - 1) >= row) {
    [[categories objectAtIndex:row]objectForKey:@"name"];
    ....
}

Answer 2

错误的是你要求的数组元素不存在。