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# numberOfRows(in:)

Returns the number of records managed for `aTableView` by the data source object.

```
@MainActor optional func numberOfRows(in tableView: NSTableView) -> Int
```

## Parameters

`tableView`

The table view that sent the message.

## Return Value

The number of rows in `aTableView`.

## Discussion

An instance of [`NSTableView`](/documentation/AppKit/NSTableView) uses this method to determine how many rows it should create and display. Your [`numberOfRows(in:)`](/documentation/AppKit/NSTableViewDataSource/numberOfRows(in:)) implementation is called very frequently, so it must be efficient.

Both view-based table views and cell-based table views must implement this method.

> Note:
> This method is mandatory unless your application is using Cocoa bindings for providing data to the table view.

## See Also

[`NSTableView`](/documentation/AppKit/NSTableView)

A set of related records, displayed in rows that represent individual records and columns that represent the attributes of those records.


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