sorting UITableView into sections - ios

Question

I'm new to swift & Xcode (teaching myself via tutorials and stackoverflow). I've written some code that adds places to a list in a TableView and now I am trying to sort that list of places into sections.
Specifically, I have a ViewController where I input name, neighborhood and friend (all strings) and this adds a Place to the bottom of my TableView.
I want to group this list of places by neighborhood, and display all the places in the same neighborhood together in a section, using the neighborhood string as the section header.
I'm close, but I'm not indexing my sections correctly. indexPath.section I believe is what I'm missing..
So far I have this code in my TableViewController:
// MARK: Properties
var places = [Place]()
override func viewDidLoad() {
super.viewDidLoad()
// Use the edit button item provided by the table view controller.
navigationItem.leftBarButtonItem = editButtonItem()
// Load any saved places, otherwise load sample data.
if let savedPlaces = loadPlaces() {
places += savedPlaces
}
else {
// Load the sample data.
loadSamplePlaces()
}
// Sort by neighborhood
places.sortInPlace { (place1, place2) -> Bool in
return place1.neighborhood < place2.neighborhood
}
}
// MARK: Getting Count, Number and Name of Neighborhoods
func getCountForNeighborhood(neighborhood:String) -> Int {
return places.filter { (place) -> Bool in
return place.neighborhood == neighborhood
}.count
}
func getNumberOfNeighborhoods() -> Int {
var neighborhoodCount = 0
var neighborhoodPrev = "Not a real neighborhood"
for place in places {
if place.neighborhood != neighborhoodPrev {
neighborhoodCount += 1
}
neighborhoodPrev = place.neighborhood
}
return neighborhoodCount
}
func getNeighborhoodForSection(section:Int) -> String {
var previousNeighborhood:String = "Not a real neighborhood"
var currentIndex = -1
for place in places {
if(place.neighborhood != previousNeighborhood) {
currentIndex += 1
}
if(currentIndex == section){
return place.neighborhood
}
previousNeighborhood = place.neighborhood
}
return "Unknown"
}
func loadSamplePlaces() {
let place1 = Place(name: "Motorino", neighborhood: "East Village", friend: "Maggles")!
let place2 = Place(name: "Bar Primi", neighborhood: "Lower East Side", friend: "Em")!
let place3 = Place(name: "El Carino", neighborhood: "Williamsburg", friend: "Ruby")!
places += [place1, place2, place3]
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
//alter this for To Try, Been To sections =2
return getNumberOfNeighborhoods()
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
let neighborhood = getNeighborhoodForSection(section)
return getCountForNeighborhood(neighborhood)
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Table view cells are reused and should be dequeued using a cell identifier.
let cellIdentifier = "PlaceTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! PlaceTableViewCell
// Fetches the appropriate place for the data source layout.
let place = places[indexPath.row]
cell.placeLabel.text = place.name
cell.neighborhoodLabel.text = place.neighborhood
cell.friendLabel.text = place.friend
return cell
}
//Add section headers
override func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return getNeighborhoodForSection(section)
}
I'm fairly certain it's an issue with my cellForRowAtIndexPath method. I think I'm missing some code to properly index the data into sections...
Current build displays

Answer 1

You've made a mess with sections.
In method tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) you're taking data from the places array based on the row of the indexPath.
But you don't "talk" about sections at all. That's why you tell the data source delegate to take the data of those 2 place objects regardless of the section it's asking you.
You've made a data structure in a relational style like this:
neighbourhood1 - place1
neighbourhood1 - place2
neighbourhood2 - place3
neighbourhood2 - place4
neighbourhood3 - place5
neighbourhood3 - place6
And believe me, it's really hard to interface this data structure with the UITableView data source concept, cause it's really hard to determine the section index from the single data.
Try to arrange your data in a tree like this:
neighbourhood1:
- place1
- place2
neighbourhood2:
- place3
- place4
neighbourhood3:
- place5
- place6
In an array of arrays, and then it will be simple, cause the indexPath pair (section, row) will match the indexes of your places[section][row]:
neighbourhood1: (section 0)
- place1 (path 0.0)
- place2 (path 0.1)
neighbourhood2: (section 1)
- place3 (path 1.0)
- place4 (path 1.1)
neighbourhood3: (section 2)
- place5 (path 2.0)
- place6 (path 2.1)

Answer 2

I do concur with the other answer: this will be easier if your store your data in a two-dimensional array organized by neighborhood first, then place second, then access the data as:
let place = places[indexPath.section, indexPath.row];
However, to your specific questions and current code, I see two things here. First, your sample data has a single item per neighborhood, but your table is showing two rows per neighborhood. That indicates that your numberOfRowsInSection function is returning 2 when we expect it to be 1. Make sure your getNeighborhoodForSection is returning the right section. Then look at why getCountForNeighborhood isn't returning 1 for each section. (As an aside, you probably already know this, but getNeighborhoodForSection assumes your data is always sorted by neighborhood. If you insert a new neighborhood out of order, you'll run into problems).
Second, cellForRowAtIndexPath you always pull data by the indexPath.row number. When you enter this function for each neighborhood, the indexPath.row number will always restart at 0 for each section (neighborhood). And therefore you'll pull the 1st item out of places (Motorino) for the first row in every section. That's why you see the same list of places repeated in each section.
Once you have the right number of rows per neighborhood, In cellForRowAtIndexPath you need to:
Get the neighborhood for index.section using your getNeighborhoodForSection(index.section);
Search through places until you find that neighborhood and save the index of the starting point, which I'll call neighborHoodStartIndex
let place = places[neighborHoodStartIndex + indexPath.row]
For debugging purposes, I'd suggest making a different number of sample places in each neighborhood. It'll be a little easier to spot problem patterns when you expect different numbers of rows in each section.