Open Radar

 
Summary:
In iOS7, the hash implementation for UIMutableIndexPath and NSIndexPath appear to have changed. If you have a mutable and non-mutable index path with the same value, they return true for isEqual: but have differing hash values. In iOS6 the hash values would be equal.

The UITableViewDelegate method - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath provides a UIMutableIndexPath. If, for example, the program keeps an NSSet of NSIndexPaths and checks the membership of the supplied indexPath, there will be false negatives due to the hash difference.

Steps to Reproduce:
Run the attached Xcode project, or:

Implement the UITableViewDelegate method
 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath

with the following code:
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSIndexPath *copiedIndexPath = [NSIndexPath indexPathForRow:indexPath.row inSection:indexPath.section];
    if ([indexPath isEqual:copiedIndexPath]
        && indexPath.hash != copiedIndexPath.hash
    ) {
        NSLog(@"if isEqual: is true, hash should be equal");
        NSLog(@"%@", indexPath);
        NSLog(@"%@ %@", [indexPath class], [copiedIndexPath class]);
        NSLog(@"%d", [indexPath isEqual:copiedIndexPath]);
        NSLog(@"%u %u", copiedIndexPath.hash, indexPath.hash);
    }

    return 0.f;
}


Expected Results:
The if statement would never evaluate to true.

Actual Results:
The if statement evaluates to true for index paths that are not (0, 0).