Array Won't Sort Correctly : Swift 4

Question

I was trying to sort an array of custom objects but for some reason, the code that worked a few weeks back won't work anymore. It is supposed to check if 0ドル and 1ドル have the same date, and if they do, it is supposed to sort the array by id, but currently it won't sort correctly and when I print the array, I get the following output:

11-07-2017 : 1
11-07-2017 : 10
11-07-2017 : 11
11-07-2017 : 12
11-07-2017 : 13
11-07-2017 : 14
11-07-2017 : 15
11-07-2017 : 16
11-07-2017 : 17
11-07-2017 : 18
11-07-2017 : 19
11-07-2017 : 2
11-07-2017 : 20
11-07-2017 : 3
11-07-2017 : 4
11-07-2017 : 5
11-07-2017 : 7
11-07-2017 : 8
11-07-2017 : 9
11-08-2017 : 1
11-08-2017 : 2
11-09-2017 : 1
11-09-2017 : 2

As can be seen above, the dates that only have a few entries sort correctly, but the dates with more entries (11-07-17) don't.

Below is my code:

Model for the Array:

struct BalanceUser {
 var id = ""
 var name = ""
 var date = ""
}

Current Sorting Code:

self.sortedTableArray.sort(by: {
 if 0ドル.date != 1ドル.date {
 return 0ドル.date < 1ドル.date
 } else {
 return 0ドル.id < 1ドル.id
 }
})

Firebase Code (As Requested):

ref.child("Admin").child("Balances").observeSingleEvent(of: .value, with: { (snapshot) in
 let value = snapshot.value as? NSDictionary
 if value!.count > 1 {
 let specificValues = value?.allKeys
 for balanceUser in specificValues! {
 var user = BalanceUser()
 user.date = balanceUser as! String
 if balanceUser as? String != "balance" {
 var i = 0
 var counter = 0
 while i < 101 {
 self.ref.child("Admin")
 .child("Balances")
 .child(balanceUser as! String)
 .child(String(i))
 .observeSingleEvent(of: .value, with: { (snapshot) in
 let nameValue = snapshot.value as? NSDictionary
 if nameValue != nil {
 user.id = counter
 var j = 0
 while j < (nameValue?.count)! {
 let item = nameValue?.allKeys[j] as? String
 var aItem = ""
 if let item = nameValue?.allValues[j] as? String {
 aItem = item
 } else if let item = nameValue?.allValues[j] as? NSNumber {
 aItem = String(describing: item)
 } else if let item = nameValue?.allValues[j] as? Int {
 aItem = String(describing: item)
 }
 if item == "name" {
 user.name = aItem
 } else if item == "money" {
 user.money = aItem
 } else if item == "balance" {
 user.balance = aItem
 } else if item == "status" {
 user.status = aItem
 }
 j += 1
 }
 let dateFormatter = DateFormatter()
 dateFormatter.dateFormat = "MM-dd-yyyy"
 if user.date.components(separatedBy: "-")[0] == dateFormatter.string(from: Date()).components(separatedBy: "-")[0] {
 self.sortedTableArray.append(user)
 self.sortedTableArray.sort(by: { (object1, object2) -> Bool in
 if object1.date == object2.date {
 return object1.id < object2.id
 } else {
 return object1.date < object2.date
 }
 })
 }
 self.tableArray.append(user)
 self.tableArray.sort(by: { (object1, object2) -> Bool in
 if object1.date == object2.date && object1.year == object2.year {
 return object2.id > object1.id
 } else {
 return object1.date < object2.date || object1.year < object2.year
 }
 })
 self.tableView.reloadData()
 }
 counter += 1
 }) { (error) in
 print(error.localizedDescription)
 }
 i += 1
 }
 }
 }
 } else {
 self.view.makeToast(message: "No Users Found in Database")
 }
 }) { (error) in
 print(error.localizedDescription)
 }

• rmaddy: It is sorting properly. Your ids are strings so they are sorted alphabetically, not numerically.
• kingkps: Oh, I did not realize that. So if I store the id as an integer and sort it that way, it will work correctly, right?
• rmaddy: BTW - your dates won't sort property as strings in that format. They need to be formatted as yyyy-MM-dd to sort properly as strings.
• rmaddy: If you want your ids treated as numbers then don't use a string. Use a numeric data type. Or use code that sorts the strings as numbers.
• rmaddy: No, your dates are not sorting correctly. Add a date of 02-15-2018 and see what happens. Or 12-25-2016.

Answer 1

It's sorting absolutely correct as you write it.

Strings comparing work for every char from the beginning. If first char is equal then check second and so on. In your results "10" < "2", cause unicode of "1"-character is less then "2"-character code.

You need to compare do it like this:

self.sortedTableArray.sort(by: {
 if 0ドル.date != 1ドル.date {
 return 0ドル.date < 1ドル.date
 } else {
 return Int(0ドル.id) ?? 0 < Int(1ドル.id) ?? 0
 }
})

Also your should compare dates as Date not Strings.

Answer 2

Just use the string comparator which sorts numeric strings properly

self.sortedTableArray.sort(by: {
 if 0ドル.date != 1ドル.date {
 return 0ドル.date < 1ドル.date
 } else {
 return 0ドル.id.localizedStandardCompare(1ドル.id) == .orderedAscending
 }
})

or the standard compare selector with option .numeric

return 0ドル.id.compare(1ドル.id, options: .numeric) == .orderedAscending

Answer 3

You can extend your BalanceUser adding computed properties to return year, month, day and id value. Next just make your struct conform to Comparable protocol:

extension BalanceUser: Comparable {
 var year: Int {
 return Int(date.suffix(4))!
 }
 var month: Int {
 return Int(date.prefix(2))!
 }
 var day: Int {
 return Int(date.prefix(5).suffix(2))!
 }
 var idValue: Int {
 return Int(id)!
 }
 static func ==(lhs: BalanceUser, rhs: BalanceUser) -> Bool {
 return lhs.date == rhs.date && lhs.id == rhs.id
 }
 static func <(lhs: BalanceUser, rhs: BalanceUser) -> Bool {
 return (lhs.year, lhs.month, lhs.day, lhs.idValue) < (rhs.year, rhs.month, rhs.day, rhs.idValue)
 }
}

---

Now you can simply sort your custom type array:

sortedTableArray.sort()

• rmaddy: Not really any reason to separately compare the year, month, and day in the == operator. Just compare date and id as-is.
• Leo Dabus: @rmaddy thats true
• Martin R: Tuples can be used to sort by multiple criteria, see stackoverflow.com/a/37612765/1187415. – In this case: return (lhs.year, lhs.month, lhs.day) < (rhs.year, rhs.month, rhs.day)
• Martin R: Or (lhs.year, lhs.month, lhs.day, lhs.idValue) < (rhs.year, rhs.month, rhs.day, rhs.idValue)
• Martin R: GitHub seems to be offline. And yes, it is implemented for tuples up to arity 6.

Answer 4

Please check the following code:

let array = ["11-07-2017", "14-07-2017", "10-07-2017","08-07-2017"]
var convertedArray: [Date] = []
var dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-MM-yyyy"// yyyy-MM-dd"
for dat in array {
 let date = dateFormatter.date(from: dat)
 if let date = date {
 convertedArray.append(date)
 }
 }
var ready = convertedArray.sorted(by: { 0ドル.compare(1ドル) == .orderedDescending })
print(ready)

• Upholder Of Truth: This answer completely misses the issue of sorting the id part which is what is actually causing the issue. The date part is sorting correctly.