Sorting rows within a section in a UITableView - swift

Question

I'd like to sort my items within a section of a UITableView. So in the below screenshot under the "N/A" section "Dad" would need to come first followed by "Hi". In the "Last 7d" section the items would also need to be sorted alphabetically.
I can't figure out where in the table's lifecycle to sort the items. Sorting my model (the list of items) and using it with the UITableView doesn't seem to help.
EDIT
Please find below my code. I now understand that the best thing to do is to not only sort but also filter my items into separate lists, one for each displayed section. This is better from a performance perspective, since tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) keeps getting called for each displayed item. Eventhough it doesn't get called for the overall total number of items, it would still be sloppy to sort over and over again the master list of items each time a new item is displayed.
My concern is that the number of sections can vary dynamically and it could reach quite a high number (up to 8). The grouping into sections can also vary - either sections by priority or by due date. So, I think I need to create a more complex data structure for my model -- instead of the current simple list and functions that filter it and sort it at "display time" a class with multiple sorted lists, one for each section, maybe. I will need to create several of these classes, depending on what the user groups by. And these classes will also need to have custom functions to find in the model the item that was tapped / updated based on the indexPath. Makes sense though.
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// Since I register the TableViewCell class to be used to create a new table view cell in viewDidLoad(), when tableView:cellForRowAtIndexPath: next needs a table cell, your new class will be used automatically.
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TableViewCell
// special case for empty, "add reminder" cell
cell.toDoItem = nil
if (indexPath as NSIndexPath).section >= ReminderDue.sections.count {
return cell
}
// If a proper reminder is chosen
if let definiteList = self.groupByDelegator.getReminderList() {
// Take the master list of items and return a filtered sublist of items that belong to that section
let sectionItems = ReminderDue.getReminders(definiteList, inSection: ReminderDue.sections[(indexPath as NSIndexPath).section])
// Do the sorting here
let QUERY_SETTINGS_KEY = "querysettings"
if let definiteIndex = reminderListController.indexOfDisplayedCalInMenu {
let definiteSetting = loadQuerySetting(definiteIndex, saveKey: QUERY_SETTINGS_KEY)
sectionItems.sortBy(definiteSetting.sortBy)
}
cell.selectionStyle = .none // This gets rid of the highlighting that happens when you select a table cell.
// If a reminder (i.e., not the empty row at the end.)
if !sectionItems.list.isEmpty && (indexPath as NSIndexPath).row < sectionItems.count {
// cell.delegate = self
cell.delegate = updateReminderDelegate // Assign as the TableViewCell's delegate the ReminderMainVC (via its UpdateReminderDelegate)
let rem = sectionItems.list[(indexPath as NSIndexPath).row]
cell.toDoItem = rem
}
}
return cell
}

Answer 1

You haven’t shared your code so I can’t use your specific values, but here is an example. I’m assuming you have an array of objects that is used to populate the tableview and that these objects have a property for their section ("low" or "none" priority in your case) and one for their visible name value ("Vic’s" or "Dad" as examples in your case).
Edit: With thanks to #rmaddy
You should sort the array first by the name property and then filter it into a new array for each section. Because this is a stable sorting algorithm, the alphabetic order of the names will persist. Do this when you Load your data, which might be in viewDidLoad():
override viewDidLoad() {
super.viewDidLoad()
// mainArray is your array of data model objects. You will need a strong reference to it and the section arrays so declare them at the top of your view controller class.
// This will sort your array by name
mainArray.sort() { $0.name < $1.name }
// Setup section arrays (I have assumed your objects have a property called priority
// No priority
noPriorityArray = mainArray.filter() { $0.priority == "none" }
// Low priority
lowPriorityArray = mainArray.filter() { $0.priority == "low" }
}
Then access these arrays in the tableview delegate method:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell... // Put your code for getting cell here
// Now code to get cell for each section
if indexPath.section == 0 {
// No priority
cell.textLabel.text = noPriorityArray[indexPath.row]?.name
} else if indexPath.section == 1 {
// Low priority
cell.textLabel.text = lowPriorityArray[indexPath.row]?.name
}
// Other code for other sections or other setup etc.
return cell
}

Answer 2

let sortedItems = arrayOfItems.sorted(by: <)