在Swift中使用协议和委托将数据从UITableViewDataSource传递到UIViewController

Question

I'm trying to pass data from a UITableViewDataSource to a UIViewController when a table row is selected. I think I'm pretty close.

Protocol

protocol BusDataDelegate {
    func didSelectRow(row: NSIndexPath, data: Route)
}

Data Source

class BusUITableView: NSObject, UITableViewDelegate, UITableViewDataSource {

    var busDataDelegate: BusDataDelegate?

    var routeService: RouteService = RouteService()

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

        var busRoutes: [Route] = routeService.retrieve()
        return busRoutes.count
    }

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

        var cell:BusUITableViewCell = tableView.dequeueReusableCellWithIdentifier("cell") as BusUITableViewCell

        var busRoutes: [Route] = routeService.retrieve()

        cell.routeName.text = busRoutes[indexPath.row].name
        cell.routeNumber.text = busRoutes[indexPath.row].id
        return cell
    }

    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

        var busRoutes: [Route] = routeService.retrieve()

        busDataDelegate?.didSelectRow(indexPath, data: busRoutes[indexPath.row])
        println("You selected cell #\(indexPath.row)!")

    }

}

View Controller - abbreviated

class ViewController: UIViewController, MKMapViewDelegate, BusDataDelegate {

    func didSelectRow(row: NSIndexPath, data: Route) {
        println("Row: \(row) Data: \(data)")
    }

}

Answer 1

The issue is you only declared the busDataDelegate object, not assigned anything to it or not allocated it.

You are declaring it like:

var busDataDelegate: BusDataDelegate?

And using it like:

busDataDelegate?.didSelectRow(indexPath, data: busRoutes[indexPath.row])

But never assigned anything to that object or allocated it, that's the problem.