Question

I am using ARC and want to create a method that passes in an indexPath by reference so I can change its value:

-(void)configureIndexPaths:(__bridge NSIndexPath**)indexPath anotherIndexPath:(__bridge NSIndexPath**)anotherIndexPath
{
      indexPath = [NSIndexPath indexPathForRow:*indexPath.row + 1 inSection:0];
      anotherIndexPath = [NSIndexPath indexPathForRow:*anotherIndexPath.row + 1 inSection:0];
}

But this gives me a property row not found error. How can I address this.

And another conceptual question: if my my goal is just to change the value of indexPath that was passed in to the method, couldn’t passing by pointer also do that? Why would I choose to pass by reference rather than pass by pointer?

Answer 1

This is how you would do this:

-(void) configureIndexPaths:(NSIndexPath*__autoreleasing *)indexPath anotherIndexPath:(__bridge NSIndexPath*__autoreleasing *)anotherIndexPath
{
    if (indexPath)
        *indexPath = [NSIndexPath indexPathForRow:[(*indexPath) row] + 1 inSection:0];
    if (anotherIndexPath)
        *anotherIndexPath = [NSIndexPath indexPathForRow:[(*indexPath) row] + 1 inSection:0];
}

You should use __autoreleasing, so that the objects are properly autoreleased when they are created, as well as checking for a NULL pointer being passed in. If you want a true pass-by-reference, look into objc++ and a NSIndexPath *&.