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How to register a cell for UITableViewCell reuse

Paul Hudson       @twostraws

Reusing table view cells has been one of the most important performance optimizations in iOS ever since iOS 2.0, but it was only with iOS 6.0 that the API got cleaned up a little with the addition of the register() method.

There are two variants to register, but both take a parameter called forCellReuseIdentifier, which is a string that lets you register different kinds of table view cells. For example, you might have a reuse identifier "DefaultCell", another one called "Heading cell", another one "CellWithTextField", and so on. Re-using different cells this way helps save system resources.

If you want to use register() with a Swift class, you provide a table view cell class as its first parameter. This is useful if your cell is defined entirely in code. As an example, this uses the default UITableViewCell class:

tableView.register(UITableViewCell.self, forCellReuseIdentifier: "DefaultCell")

You can then dequeue that cell like this:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "DefaultCell")!
    return cell
}

If there aren't any cells created that can be reused, iOS will automatically create them – this API really is very easy.

The other option is to use register() with an Interface Builder nib file, like this:

tableView.register(UINib(nibName: "yourNib", bundle: nil), forCellReuseIdentifier: "CellFromNib")

Although knowing the above code is definitely useful, if you're using storyboards you will find it easier to create prototype cells and give them a reuse identifier directly inside Interface Builder.

Available from iOS 6.0 – see Hacking with Swift tutorial 33

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