Does indexpath.row take care of iterating an array?

Question

I'm working through a UITableView tutorial and I've become curious about array iteration as I implement the UITableViewDataSource methods. When we call indexPath.row, is this calling a for loop for us behind the scenes? I'm asking because months back when I was learning to use data from a webservice (I've forgotten the exact steps of how I did it precisely) but I believe I needed to iterate over the array in order to present the information in the console.

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        // Create an instance of UITableViewCell, with default appearance
        let cell = UITableViewCell.init(style: .value1, reuseIdentifier: "UITableViewCell")

        // Set the text on the cell with the description of the item instance that is at the nth index of the allItems array, where n = row this cell will appear in on the tableview
        let item = itemStore.allItems[indexPath.row]

        cell.textLabel?.text = item.name
        cell.detailTextLabel?.text = "$\(item.valueInDollars)"

        return cell
    }

Am I correct in thinking that the indexPath.row method is iterating over the array for us behind the scenes?

let item = itemStore.allItems[indexPath.row]

Answer 1

No, calling indexPath.row does not iterate through all rows for you. It's just a variable sent to cellForRowAt that you can access and use to create your cell. It contains information about which row in which section the function cellForRowAt was called for.

However, cellForRowAt is actually called every time a cell is going to be visible on your tableVIew. Imagine you have a dataSource with 100 items and it is possible to only see 10 cells at a time. When the tableView gets initially loaded, cellForRowAt will get called 10 times. Then, if you scroll your tableView to show 3 more cells, cellForRowAt will get called 3 more times.