How to know which methods are required in swift?

protocol UITableViewDataSource : NSObjectProtocol {

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int

    // Row display. Implementers should *always* try to reuse cells by setting each cell's reuseIdentifier and querying for available reusable cells with dequeueReusableCellWithIdentifier:
    // Cell gets various attributes set automatically based on table (separators) and data source (accessory views, editing controls)

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell

    optional func numberOfSectionsInTableView(tableView: UITableView) -> Int // Default is 1 if not implemented

    optional func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? // fixed font style. use custom view (UILabel) if you want something different
    optional func tableView(tableView: UITableView, titleForFooterInSection section: Int) -> String?

    // Editing

    // Individual rows can opt out of having the -editing property set for them. If not implemented, all rows are assumed to be editable.
    optional func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool

    // Moving/reordering

    // Allows the reorder accessory view to optionally be shown for a particular row. By default, the reorder control will be shown only if the datasource implements -tableView:moveRowAtIndexPath:toIndexPath:
    optional func tableView(tableView: UITableView, canMoveRowAtIndexPath indexPath: NSIndexPath) -> Bool

    // Index

    optional func sectionIndexTitlesForTableView(tableView: UITableView) -> [AnyObject]! // return list of section titles to display in section index view (e.g. "ABCD...Z#")
    optional func tableView(tableView: UITableView, sectionForSectionIndexTitle title: String, atIndex index: Int) -> Int // tell table which section corresponds to section title/index (e.g. "B",1))

    // Data manipulation - insert and delete support

    // After a row has the minus or plus button invoked (based on the UITableViewCellEditingStyle for the cell), the dataSource must commit the change
    // Not called for edit actions using UITableViewRowAction - the action's handler will be invoked instead
    optional func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath)

    // Data manipulation - reorder / moving support

    optional func tableView(tableView: UITableView, moveRowAtIndexPath sourceIndexPath: NSIndexPath, toIndexPath destinationIndexPath: NSIndexPath)
}