无法调用' indexOf'参数类型为'(ChecklistItem)'的参数列表

当我编写代码以使用indexOf从数组中查找项目时，它向我显示了上述错误.这是我的代码:-

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)
        }
    }