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POHow to properly use "dequeueReusableCellWithIdentifier:" with multiple identifiers?
 

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  1. POHow to properly use "dequeueReusableCellWithIdentifier:" with multiple identifiers?
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    <p>I have a Core Data backed table view, that show a list of editable fields, for different field types I have different UTableViewCells with different cell identifiers. When I scroll too quickly in the simulator or try to "bounce" past the last cell, I get a crash, saying that <strong>UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath</strong>. The whole problem goes away if I remove the dequeueReusableCellWithIdentifier: steps. Which means my table view is less efficient. I'm at most using 20 fetched objects (more along the lines of 8-10) in my table view, so the inefficiency might be a minor issue. I'd just like to know if I'm doing something the wrong way. </p> <pre><code> - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { Field *aField = [self.fetchedResultsController objectAtIndexPath:indexPath]; static NSString *CellIdentifier = @"Cell"; static NSString *ChoiceIdentifier = @"ChoiceCell"; static NSString *SwitchIdentifier = @"SwitchCell"; UITableViewCell *cell; if ([aField.fieldType isEqualToString:@"choice"] || [aField.fieldType isEqualToString:@"date"] || [aField.fieldType isEqualToString:@"multiChoice"] ) { NSLog(@"ChoiceCell"); cell = [tableView dequeueReusableCellWithIdentifier:ChoiceIdentifier]; if (cell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell" owner:self options:nil]; } } } else if ([aField.fieldType isEqualToString:@"boolean"]){ NSLog(@"SwitchCell"); cell = [tableView dequeueReusableCellWithIdentifier:SwitchIdentifier]; if (cell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell" owner:self options:nil]; } } } else { NSLog(@"Cell"); cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell" owner:self options:nil]; } } } cell = editableCell; self.editableCell = nil; // Configure the cell... [self configureCell:cell atIndexPath:indexPath]; return cell; } </code></pre> <p><strong>Additional Details:</strong> The editableCell is being set as in each of the NIBs that correspond to the custom cells. I tried more directly setting this by saying</p> <pre><code>dynamicCell = [[[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil] objectAtIndex:0]; </code></pre> <p>but still had the same problem. It should never return nil. The all the NIBs are being loaded as long as I don't scroll too fast. I've double and triple checked the NIB names to make sure.</p> <p><strong>Here's the updated working code:</strong></p> <pre><code>- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath </code></pre> <p>{</p> <pre><code>Field *aField = [self.fetchedResultsController objectAtIndexPath:indexPath]; static NSString *CellIdentifier = @"Cell"; static NSString *ChoiceIdentifier = @"ChoiceCell"; static NSString *SwitchIdentifier = @"SwitchCell"; if ([aField.fieldType isEqualToString:@"choice"] || [aField.fieldType isEqualToString:@"date"] || [aField.fieldType isEqualToString:@"multiChoice"] ) { NSLog(@"ChoiceCell"); dynamicCell = [tableView dequeueReusableCellWithIdentifier:ChoiceIdentifier]; if (dynamicCell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell" owner:self options:nil]; } } } else if ([aField.fieldType isEqualToString:@"boolean"]){ NSLog(@"SwitchCell"); dynamicCell = [tableView dequeueReusableCellWithIdentifier:SwitchIdentifier]; if (dynamicCell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell" owner:self options:nil]; } } } else { NSLog(@"Cell"); dynamicCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (dynamicCell == nil) { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell-iPad" owner:self options:nil]; } else { [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell" owner:self options:nil]; } } } UITableViewCell *cell; cell = dynamicCell; self.dynamicCell = nil; // Configure the cell... [self configureCell:cell atIndexPath:indexPath]; return cell; </code></pre> <p>}</p>
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    1. COAre your reuseIdentifiers set properly in the nibs? You shouldn't have a special if-branch for iPad. NSBundle can load the right nib by itself. To simplify the code, you should also call [bundle loadNib:filename] only once and use the if-branches only to set a variable "NSString* filename".
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      1. POHow to properly use "dequeueReusableCellWithIdentifier:" with multiple identifiers?
      1. USSulthan
 

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