StackOverflow2013

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POCell of UICollectionView not always refreshed after a scroll
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copied!<p>I have defined in my Storyboard (iPad) a view that contains a <code>UICollectionView</code>, at the bottom of the view there's also a <code>UIToolbar</code>. In the <code>UICollectionView</code> I have added a <code>UICollectionViewCell</code> (implemented by an <code>iPadCellCollectionViewCell</code> class) that contains a another view that is a Core-Plot Graph (a <code>CPTGraphHostingView</code> class).</p> <p>I have a class called X that implements the <code>UICollectionViewDelegate</code> and <code>UICollectionViewDataSource</code>.</p> <p>In the class X, I build for each cell of my view (in <code>ViewDidLoad</code>) the Core-Plot Graph and I have the following code to link the graph to the cell of the <code>UICollectionViewCell</code></p> <pre><code>- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { static NSString* cellId = @"ChartCollectionId"; iPadCellCollectionViewCell* cell = [self.theCollectionView dequeueReusableCellWithReuseIdentifier:cellId forIndexPath:indexPath]; MyChart* chart = [_charts objectAtIndex:indexPath.row]; cell.hostingView.hostedGraph = chart.barChart; return cell; </code></pre> <p>}</p> <p>It's working fine, all my Graphs are correctly displayed on the screen. The issue happens when the user scroll the view, then one or several cells become "blank". I really don't understand why.</p> <p>I have found a workaround, instead of adding the <code>CPTGraphHostingView</code> in the <code>UICollectionViewCell</code> in the Interface Builder, I build it myself and the previous code becomes:</p> <pre><code>- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { static NSString* cellId = @"ChartCollectionId"; iPadCellCollectionViewCell* cell = [self.theCollectionView dequeueReusableCellWithReuseIdentifier:cellId forIndexPath:indexPath]; [cell.contentView addSubview:[_hostingViews objectAtIndex:indexPath.row]]; return cell; </code></pre> <p>}</p> <p>With this code everything is working fine. Is there any explanations why it's not working when I'm adding the <code>CPTGraphHostingView</code> in the <code>UICollectionViewCell</code> with the IB?</p> <p>Is it an issue to call "addSubview" each time the method is called? No memory leaks?</p>

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