无法从NSMutable数组存储和检索值

Question

I'm storing a value in a NSMutableArray ...however when I try to retrieve it, it doesn't find it.

My aim is to look for beacon major id. If a new beacon major id is found I save it in the array. So the next time when I read the beacon major id, if it is already present in the array I don't use it.

for (int i=0; i<numberOfBeacondsInRange; i++) 
{

    NSLog(@"Processing current beacon: %d of %d", i, numberOfBeacondsInRange-1);

    ESTBeacon *currentBeacon = [self.beaconsArray objectAtIndex:i];
    // not able to retrive values from the array to compare

    BOOL isPresent=NO;

    for (int j=0; j<100; j++)
    {
        if ([visitedBeaconsArrayMajor objectAtIndex:j] == currentBeacon.major)
        {
               NSLog(@"Already seen");
               isPresent=YES;
        }
     }

     if (isPresent==NO) 
     {
        [visitedBeaconsArrayMajor addObject:currentBeacon.major];
        NSLog(@"Add major:%@",currentBeacon.major);
     }
}

Answer 1

More often than not, this happens if you've not initialized your NSMutableArray property before its put to use like so visitedBeaconsArrayMajor = [[NSMutableArray alloc] init]; resulting in it being nil .