为什么在这个循环中要销毁NSMutableArray?

是阵列的性能被破坏了。

这是数组的.h:

    NSMutableArray * arrayOfPerformances;
}
@property (nonatomic, retain) NSMutableArray * arrayOfPerformances;

还有有循环的.m:

[dataArray release];
[dataDictionary release];
dataArray = [[NSMutableArray alloc] init];
dataDictionary = [[NSMutableDictionary alloc] init];

NSDate * CurrentDate = start;
int i = 0;

NSMutableArray * arrayOfPerformancesForCurrentDate = [[NSMutableArray alloc] init];
while(YES)
{
    i = 0;
    if ([arrayOfPerformancesForCurrentDate count] > 0)
    {
        [arrayOfPerformancesForCurrentDate removeAllObjects];   
    }

    for (i; i < self.arrayOfPerformances.count; i++)
    {
        Performance * performanceItem = [[Performance alloc] init]; 
        performanceItem = [self.arrayOfPerformances objectAtIndex:i];

        NSString * sPerformanceDate = [performanceItem.sDate substringToIndex:10];
        NSString * sCurrentDate = [CurrentDate dateDescription];

        if([sPerformanceDate isEqualToString:sCurrentDate])
        {
            [arrayOfPerformancesForCurrentDate addObject:performanceItem];
        }

        [performanceItem release];
    }

    if ([arrayOfPerformancesForCurrentDate count] >= 1)
    {
        [dataDictionary setObject:arrayOfPerformancesForCurrentDate forKey:CurrentDate];
        [dataArray addObject:[NSNumber numberWithBool:YES]];
    }
    else
    {
        [dataArray addObject:[NSNumber numberWithBool:NO]];
    }

    TKDateInformation info = [CurrentDate dateInformation];
    info.day++;
    CurrentDate = [NSDate dateFromDateInformation:info];
    if([CurrentDate compare:end]==NSOrderedDescending) break;
}

任何帮助都将不胜感激。我不明白为什么会这样?