释放NSKeyedUnarchiver导致崩溃

-(id)func
{
        NSData* data = [[NSData alloc] initWithContentsOfFile:aFilePath];
    NSKeyedUnarchiver* unachiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
    id object = [unachiver decodeObjectForKey:key];
    [unachiver finishDecoding];
        [unachiver release];
        [data release];
    return object;
}

id anotherObject = [self func];

decodeObjectForKey:

anotherObject

id anotherObject = [[self func] retain];