title: UICollectionView cell reuse seems to shuffle cells
body: <p>I am currently trying to implement a simple two-row UICollectionView. Because I already had this issue when using a more complex data source involving Core Data I made it just an NSArray containing some strings. Still the problem is the same. </p>
  
  <pre><code>- (NSArray *)collectionViewData
  {
      return @[@"zero",@"one",@"two",@"three",@"four",@"five",@"six",@"seven",@"eight",@"nine",@"ten",@"eleven",@"twelve",@"thirteen",@"fourteen",@"fifteen",@"sixteen", @"seventeen"];
  }
  
  - (void)viewWillAppear:(BOOL)animated
  {
      [super viewWillAppear:animated];
  
      if (!self.collectionView) {
          UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init];
          flowLayout.itemSize = CGSizeMake(160, 120);
          flowLayout.minimumInteritemSpacing = 0;
          flowLayout.minimumLineSpacing = 10;
          self.collectionView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
          self.collectionView.dataSource = self;        
          [self.collectionView registerClass:[BYCollectionViewCell class] forCellWithReuseIdentifier:@"CELL_ID"];
          [self.view addSubview:self.collectionView];
      }
  }
  
  - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
  {
      return [self.collectionViewData count];
  }
  
  - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {
      BYCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CELL_ID" forIndexPath:indexPath];
      cell.title = self.collectionViewData[indexPath.row];
      return cell;
  }
  </code></pre>
  
  <p><a href="http://bytolution.com/scrnsht.png" rel="nofollow noreferrer">http://bytolution.com/scrnsht.png</a></p>
  
  <p>As you can see, the cells are in the wrong order. When I set the <code>minimumLineSpacing</code> to 0 they even change their position.</p>
  
  <p>How can I implement UICollectionView correctly?</p>