CODEWITHSUNDEEP
iosswift
kjakm
kjakm

Reputation: 131

Sort a Dictionary where the keys are date strings

I have a Dictionary. Each key is a date in the format of "dd-mm-yyyy"". The values are arrays of objects. I would like to sort the dictionary by date so that when I display each date as a section in a table view they are in chronological order.

  let sortedDict = self?.entriesDict.sorted(by: { $0.key > $1.key })

I think the above could possibly work if I reversed the date format however it is not returning a swift Dictionary (I think it is returning an NSDictionary).

Upvotes: 0

Views: 82

Answers (1)

David Pasztor
David Pasztor

Reputation: 54755

A Dictionary is an unsorted collection by definition (an NSDictionary too). If you call sorted on a Dictionary, the return value will be of type Array<(Key,Value)>, an array of the key-value pairs in your dictionary represented as tuples.

To achieve your goals and use a Dictionary as a UITableViewDataSource, what you should do is keep a sorted array of your dictionary keys and in your data source methods, retrieve the correct key from that sorted array, then use the key to retrieve the value from the original dictionary.

I'd also suggest storing the dictionary keys as Date objects rather than date strings.

Without more context in your question, this is roughly what you should do:

let sortedKeys = entriesDict.keys.sorted()

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

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "yourCellId", for: indexPath)
    let entryKey = sortedKeys[indexPath.row]
    cell.textLabel?.text = entriesDict[entryKey]
    return cell
}

Upvotes: 1

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