Implementing closure for specific method call in Swift - ios

Question

I came across the following UITableViewController code and wanted to implement the associated classes and functions that go with them in order for me to learn a little bit more about Swift.
I'm not sure what the implementation of api.getRooms() looks like. I think it may be a closure, but I'm not entirely sure?
My question is what would api.getRooms() be returning considering there's {} usage? If anyone could explain to me what's going on that would be greatly appreciated.
api.getRooms(User.currentUser()!) { (roomsObj, error) in
if let rooms = roomsObj as? Array<Room> {
self.rooms = rooms
self.tableView.reloadData()
if (viaPullToRefresh) {
self.refreshControl.endRefreshing()
}
}
}
PullViewController.swift
class PullViewController: UITableViewController {
var rooms = Array<Room>()
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder)
// Custom initialization
assert(User.currentUser())
}
override func viewDidLoad() {
self.refreshControl = UIRefreshControl()
self.refreshControl.addTarget(self, action: Selector("refreshInvoked"), forControlEvents: UIControlEvents.ValueChanged)
refresh()
}
override func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int {
return rooms.count
}
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath:NSIndexPath!) -> UITableViewCell! {
var cell: UITableViewCell? = tableView.dequeueReusableCellWithIdentifier("Cell") as? UITableViewCell
if !cell {
cell = UITableViewCell(style: UITableViewCellStyle.Default, reuseIdentifier:"Cell")
}
let room = rooms[indexPath.row]
cell!.textLabel.textColor = UIColor.blackColor()
cell!.textLabel.text = "\(room.name)(\(room.messageCount))"
return cell
}
func refreshInvoked() {
refresh(viaPullToRefresh: true)
}
func refresh(viaPullToRefresh: Bool = false) {
let api = API()
api.getRooms(User.currentUser()!) { (roomsObj, error) in
if let rooms = roomsObj as? Array<Room> {
self.rooms = rooms
self.tableView.reloadData()
if (viaPullToRefresh) {
self.refreshControl.endRefreshing()
}
}
}
}
}
User.swift
class User {
init() {
}
class func currentUser() -> Bool {
return true
}
}
Room.swift
class Room {
var name: String
var messageCount: Int
init() {
}
}
API.swift (not sure whether this is implemented correctly).
class API {
init() {
}
func getRooms(user: User) -> (Array<Room>, String) { // ??
// ??
}
}

Answer 1

In you room class, you did not initialize the name and message count variable, in swift only optional variable can be nil
class Room {
var name: String
var messageCount: Int
init(name:String, messageCount:Int) {
self.name = name
self.messageCount = messageCount
}
}
also assert need to evaluate to bool so
assert(User.currentUser() != nil)

Answer 2

1) You are sending assert a void since your currentUser method doesn't return anything, so assert wouldn't know if this is good or bad. Therefore you need to make currentUser return a BOOL or something else if you want to use it like this, but it needs some sort of BOOL result to tell if it is asserting correctly or not. Hopefully that makes sense.
2)You are trying to feed your getRooms function a lambda function instead of running a function after the results.
--Update--
If you are wanting a completion lambda then you'll want to write getRooms like this:
func getRooms(user: User, completion: ((Array<Room>,String?) -> Void)?) -> Array<Room> {//String because I have no idea what type they want for errors
var room = Room()
room.messageCount = 0
room.name = "Room1"
var rooms = Array<Room>()
rooms.append(room)
completion?(rooms,nil)
return rooms
}
or something along those lines

Answer 3

This is how I implemented the api.getRooms() function:
API.swift
class API {
func getRooms(user: User, completion: (Array<Room>, String) -> ()) {
var room = Room(name: "Room1", messageCount: 0)
var rooms = Array<Room>()
rooms.append(room)
completion(rooms, "error")
}
}
PullViewController.swift
func refresh(viaPullToRefresh: Bool = false) {
let api = API()
if let user = User.currentUser() {
api.getRooms(user) { (roomsObj, error) in
self.rooms = roomsObj
self.tableView.reloadData()
if (viaPullToRefresh) {
self.refreshControl.endRefreshing()
}
}
}
}