How to increment String in Swift - swift

Question

I need to save files in an alphabetical order.
Now my code is saving files in numeric order
1.png
2.png
3.png ...
The problem is when i read this files again I read this files as described here
So I was thinking of changing the code and to save the files not in a numeric order but in an alphabetical order as:
a.png b.png c.png ... z.png aa.png ab.png ...
But in Swift it's difficult to increment even Character type.
How can I start from:
var s: String = "a"
and increment s in that way?

Answer 1

You can keep it numeric, just use the right option when sorting:
let arr = ["1.png", "19.png", "2.png", "10.png"]
let result = arr.sort {
$0.compare($1, options: .NumericSearch) == .OrderedAscending
}
// result: ["1.png", "2.png", "10.png", "19.png"]

Answer 2

If you'd really like to make them alphabetical, try this code to increment the names:
/// Increments a single `UInt32` scalar value
func incrementScalarValue(_ scalarValue: UInt32) -> String {
return String(Character(UnicodeScalar(scalarValue + 1)))
}
/// Recursive function that increments a name
func incrementName(_ name: String) -> String {
var previousName = name
if let lastScalar = previousName.unicodeScalars.last {
let lastChar = previousName.remove(at: previousName.index(before: previousName.endIndex))
if lastChar == "z" {
let newName = incrementName(previousName) + "a"
return newName
} else {
let incrementedChar = incrementScalarValue(lastScalar.value)
return previousName + incrementedChar
}
} else {
return "a"
}
}
var fileNames = ["a.png"]
for _ in 1...77 {
// Strip off ".png" from the file name
let previousFileName = fileNames.last!.components(separatedBy: ".png")[0]
// Increment the name
let incremented = incrementName(previousFileName)
// Append it to the array with ".png" added again
fileNames.append(incremented + ".png")
}
print(fileNames)
// Prints `["a.png", "b.png", "c.png", "d.png", "e.png", "f.png", "g.png", "h.png", "i.png", "j.png", "k.png", "l.png", "m.png", "n.png", "o.png", "p.png", "q.png", "r.png", "s.png", "t.png", "u.png", "v.png", "w.png", "x.png", "y.png", "z.png", "aa.png", "ab.png", "ac.png", "ad.png", "ae.png", "af.png", "ag.png", "ah.png", "ai.png", "aj.png", "ak.png", "al.png", "am.png", "an.png", "ao.png", "ap.png", "aq.png", "ar.png", "as.png", "at.png", "au.png", "av.png", "aw.png", "ax.png", "ay.png", "az.png", "ba.png", "bb.png", "bc.png", "bd.png", "be.png", "bf.png", "bg.png", "bh.png", "bi.png", "bj.png", "bk.png", "bl.png", "bm.png", "bn.png", "bo.png", "bp.png", "bq.png", "br.png", "bs.png", "bt.png", "bu.png", "bv.png", "bw.png", "bx.png", "by.png", "bz.png"]`
You will eventually end up with
a.png
b.png
c.png
...
z.png
aa.png
ab.png
...
zz.png
aaa.png
aab.png
...

Answer 3

Paste this code in the playground and check result. n numbers supported means you can enter any high number such as 99999999999999 enjoy!
you can uncomment for loop code to check code is working fine or not
but don't forget to assign a lesser value to counter variable otherwise Xcode will freeze.
var fileName:String = ""
var counter = 0.0
var alphabets = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
let totalAlphaBets = Double(alphabets.count)
let numFiles = 9999
func getCharacter(counter c:Double) -> String {
var chars:String
var divisionResult = Int(c / totalAlphaBets)
let modResult = Int(c.truncatingRemainder(dividingBy: totalAlphaBets))
chars = getCharFromArr(index: modResult)
if(divisionResult != 0){
divisionResult -= 1
if(divisionResult > alphabets.count-1){
chars = getCharacter(counter: Double(divisionResult)) + chars
}else{
chars = getCharFromArr(index: divisionResult) + chars
}
}
return chars
}
func getCharFromArr(index i:Int) -> String {
if(i < alphabets.count){
return alphabets[i]
}else{
print("wrong index")
return ""
}
}
for _ in 0...numFiles {
fileName = getCharacter(counter: counter)+".png"
print(fileName)
counter += 1
}
fileName = getCharacter(counter: Double(numFiles))+".png"
print(fileName)