Understanding UITableView Action Rows

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In this article, we will delve into the world of UITableView and explore how to add a custom action row when a cell is selected. We’ll examine the provided code snippets, understand the challenges faced by the user, and learn how to implement this functionality in our own iOS applications.

Background

The UITableView class is a powerful tool for displaying data in a table view format. It allows us to create rows of cells that can be customized with various types of content. In this example, we have a list of contracts that can be accepted by selecting an action row. However, the provided code snippet does not work as expected when adding a new row below the selected row.

The Challenge

The user’s issue is with the tableView:cellForRowAtIndexPath: method. When a cell is selected, it adds a new row below the selected one, but then the tableView:cellForRowAtIndexPath: method for the new row is called instead of the action row. This causes the problem because the code snippet only checks if the current row index is greater than or equal to the number of contracts, which is not sufficient to identify the added row.

Solution

To solve this issue, we need to remember which row is selected and use it to configure the correct cell type for the new row. Here’s an updated version of the tableView:cellForRowAtIndexPath: method:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *reuseID = @"contract_cell";
    
    ContractTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:reuseID];

    if(!cell)
    {
        // Load the top-level objects from the custom cell XIB.
        NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"ContractTableViewCell" owner:self options:nil];
        // Grab a pointer to the first object (presumably the custom cell, as that's all the XIB should contain).
        cell = [topLevelObjects objectAtIndex:0];
        [cell setBackgroundView:[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"contract_cell.png"]]];
    }

    NSLog(@"row?: %d", indexPath.row);
    
    if(indexPath.row == _selectedRowIndex + 1)
    {
        // Configure the action row
        cell.label.text = @"New";
        
        // Add a background image to indicate the action row
        cell.backgroundColor = [UIColor redColor];
    }
    else
    {
        Contract *contract = [_contracts objectAtIndex:indexPath.row];

        cell.label.text = @"Test";
    }

    return cell;
}

Storing the Selected Row Index

To use the above solution, we need to store the selected row index in an instance variable. We can do this by adding a new property to our view controller:

@property (nonatomic, assign) NSInteger _selectedRowIndex;

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if(!_addedRow)
    {
        _selectedRowIndex = indexPath.row;
        
        _addedRow = YES;

        [tableView deselectRowAtIndexPath:indexPath animated:NO];

        [_tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:[NSIndexPath indexPathForRow:indexPath.row+1 inSection:indexPath.section]] withRowAnimation:UITableViewRowAnimationAutomatic];
    }
}

Conclusion

In this article, we explored the UITableView action row functionality and how to add a custom action row when a cell is selected. We analyzed the provided code snippet, identified the challenges faced by the user, and implemented a solution using an instance variable to store the selected row index. By following this guide, you should be able to create a similar implementation in your own iOS applications.

Additional Tips

When working with UITableView, keep the following tips in mind:

• Always use the tableView:cellForRowAtIndexPath: method to configure cells.
• Use instance variables to store data that needs to be accessed by multiple methods.
• Test your code thoroughly to ensure it works as expected.

Common Pitfalls

Here are some common pitfalls to avoid when working with UITableView:

• Forgetting to set the tableView:cellForRowAtIndexPath: method, leading to incorrect cell configuration.
• Not using instance variables to store data that needs to be accessed by multiple methods.
• Failing to test code thoroughly, resulting in unexpected behavior.

By being aware of these pitfalls and following best practices, you can create efficient and effective UITableView implementations.

Last modified on 2023-11-14