如何将 Set 与 Table View 一起使用？

Question

I want to iterate through Set and display them in a table, but I'm getting an error that says:

Fatal error: Invalid index

Following is my code:

@NSManaged public var progress: Set<Progress>

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return progress.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    cell.textLabel?.text = progress[progress.index(progress.startIndex, offsetBy: indexPath.row)].comment
    return cell
}

Answer 1

A Set is unordered. Sort the set – for example by date – to get an array in a specific order and use this as data source array

var progresses = [Progress]() 

...   

progresses = progress.sorted{$0.date < $1.date}

Answer 2

Simply use indexPath.row as index in the Array after converting the Set<Progress> to Array<Progress> using the Array(Set) initializer.

cell.textLabel?.text = Array(progress)[indexPath.row].comment

Better Approach: Using the Array(Set) initializer in cellForRowAt each time is less efficient, also the order of elements cannot be guaranteed. It would be better to do it just once right after the progress: Set<Progress> is initialized.

var progressArray: [Progress] // set this right after `progress` is set

Then in cellForRowAt :

cell.textLabel?.text = progressArray[indexPath.row].comment