How to sort WBS format string in Realm? - swift

Question

I want to sort my Realm object, using one of it properties. It has WBS like format (1.1.3 ,1.1.11, etc) using String as it type.
I'm using RealmSwift 3.11.2 and I've already tried using sorted(by:) and it works! But the 1.1.10 and 1.1.11 will be sorted ahead of 1.1.2
This is the code that I'm using
tasks = tasks.sorted(byKeyPath: "wbs", ascending: true)
I expect the output will be ordered correctly, like [1.1.2, 1.1.10, 1.1.11].
Any help is appreciated, I'm drawing a blank here, is there any way I can do it in Realm ?

Answer 1

You may want to take a minute and do an Internet search on sorting strings.
The issue is that if you have a list of strings like this 1, 2, 3, 10 and they are sorted, they will sort to 1, 10, 2, 3.
This is because how strings are sorted; for this example they are they are generally sorted by the first letter/object in the string (1's) and then by the second letter (0) and so on, so then the strings that start with 1 get grouped up. Then 2's etc.
So you need to either pad them so the formats are the same like
01.01.02, 01.01.10, 01.01.11 etc
which will sort correctly or store the three sections in separate properties as numbers (int's)
class TriadClass {
var first = 0
var second = 0
var third = 0
init(x: Int, y: Int, z: Int) {
self.first = x
self.second = y
self.third = z
}
func getPaddedString() -> String {
let formatter = NumberFormatter()
formatter.format = "00"
let firstNum = NSNumber(value: self.first)
let secondNum = NSNumber(value: self.second)
let thirdNum = NSNumber(value: self.third)
let firstString = formatter.string(from: firstNum)
let secondString = formatter.string(from: secondNum)
let thirdString = formatter.string(from: thirdNum)
let finalString = "\(firstString!).\(secondString!).\(thirdString!)"
return finalString
}
func getPureString() -> String {
let formatter = NumberFormatter()
formatter.format = "0"
let firstNum = NSNumber(value: self.first)
let secondNum = NSNumber(value: self.second)
let thirdNum = NSNumber(value: self.third)
let firstString = formatter.string(from: firstNum)
let secondString = formatter.string(from: secondNum)
let thirdString = formatter.string(from: thirdNum)
let finalString = "\(firstString!).\(secondString!).\(thirdString!)"
return finalString
}
}
Then sort by first, second and third. To get the number for display in the UI I included to functions to format them. Note both functions could be greatly improved and shortened by I left them verbose so you could step through.
The usage would be
let myNum = TriadClass(x: 1, y: 1, z: 10)
let paddedString = myNum.getPaddedString()
print(paddedString)
let nonPaddedString = myNum.getPureString()
print(nonPaddedString)
and an output of
01.01.10
1.1.10
There are a number of other solutions as well but these two are a place to start.