Why won't this simple 'if' statement work (inside fast enumeration)?

Question

I am enumerating through the ChecklistItem entities in my table to see which ones have a priority (NSNumber attribute) of 1. checklistItems are in a to-many relationship with Checklist.

In this simple code, the first NSLog works fine, and reports that several of my ChecklistItems have a priority of 1. But the second NSLog never gets called. Why is this? I assume I'm framing the "if" statement wrong, but I don't know how.

for (ChecklistItem *eachItem in checklist.checklistItems){
    NSLog(@"Going through loop. Item %@ has priority %@.", eachItem.name, eachItem.priority);

    if (eachItem.priority == [NSNumber numberWithInt:1]) {
        NSLog(@"Item %@ has priority 1", eachItem.name);
        }
}

score 3 · Answer 1 · answered Apr 14 '11 at 16:32

3

You're comparing the pointers of the return values of eachItem.priority and [NSNumber numberWithInt:1]. You should use NSNumber's equality method.

answered Apr 14 '11 at 16:32

Cajunluke

3,103
28
28

Ravin · Accepted Answer · 2011-04-14T16:51:16.517

2

You can not compare objects as you did above. Use the following code.

for (ChecklistItem *eachItem in checklist.checklistItems){
    NSLog(@"Going through loop. Item %@ has priority %@.", eachItem.name, eachItem.priority);

    if ([eachItem.priority intValue]== 1) {
        NSLog(@"Item %@ has priority 1", eachItem.name);
        }
}

Thanks,

edited Apr 14 '11 at 16:51

answered Apr 14 '11 at 16:32

Ravin

8,544
3
20
19

But I have read that NSNumber has - (int)intValue method? Is there something wrong in documentation?please mention. – Ravin Apr 14 '11 at 16:36

score 1 · Answer 3 · answered Apr 14 '11 at 16:33

Well, you should be checking for value equality something like this:

if ( [eachItem.priority intValue] == 1 ) { ... }

However, I'm kind of surprised it doesn't accidentally work as it is, because I thought NSNumber pooled a few base instances and I'd expect 1 to be one of them. Relying on that would be very bad form, though, even if it happened to work in this case.

Why won't this simple 'if' statement work (inside fast enumeration)?

3 Answers3