ios - Cannot invoke 'indexOf' with an argument list of type '(ChecklistItem)'

Question

When I am writing code for finding an item from the array with the use of indexOf it shows me the above stated error. Here is my code:-

func addItemViewController(controller: AddItemViewController, didFinishEditingItem item: ChecklistItem)
{
    if let index = items.indexOf(item)
    {
        let indexPath = NSIndexPath(forRow: index, inSection: 0)

        if let cell = tableView.cellForRowAtIndexPath(indexPath)
        {
            configureTextForCell(cell, withChecklistItem: item)
        }
    }

Answer 1

In order to use indexOf the ChecklistItem must adopt Equatable protocol. Only by adopting this protocol the list can compare an item with other items to find the desired index