How to remove duplicates of lines of a String in Swift without lost their order?

Question

I would like to remove duplicates of lines in a string with Swift 3. I got to do it but unfortunately at the end of the process the lines lost the order. Here is my code:

// string with 7 lines and 2 duplicates (MacBook and Mac mini)
var str = "MacBook\nMacBook Pro\nMacPro\nMacBook\niMac\nMac mini\nMac mini"

var components = str.components(separatedBy: .newlines)
print(components)

// remove duplicates: first by converting to a Set
// and then back to Array (found in iSwift.org)
components = Array(Set(components))
print(components)

let newStr = components.joined(separator: "\n")
print(newStr)

EDIT: When removing duplicates, I prefer to keep the first one not the last one.

You can use [the approach shown here](http://stackoverflow.com/a/25739498/2976878) in order to maintain order. — Hamish, Mar 16 '17 at 15:19
When removing duplicates, do you wish to keep the first one or the last one? — rmaddy, Mar 16 '17 at 15:29
`let newStr = str.components(separatedBy: .newlines).reduce([]){ $0.contains($1) ? $0 : $0 + [$1] }.joined(separator: "\n")` — Leo Dabus, Mar 16 '17 at 15:42
@maddy, right question, I wish to keep the first one, I will add this info in the question. — Cue, Mar 16 '17 at 15:49

Ashley Mills · Accepted Answer · 2017-03-16T16:04:17.220

1

Tweaking @LeoDabus' comment…

let str = "MacBook\nMacBook Pro\nMacPro\nMacBook\niMac\nMac mini\nMac mini"
let components = str.components(separatedBy: .newlines)

let depDuped = components.reduce([]) {
    $0.0.contains($0.1) ? $0.0 : $0.0 + [$0.1]
}.joined(separator: "\n")

If duplicates can occur elsewhere in the string (so "A\nB\nA" would be unchanged), then

let depDuped = components.reduce([]) {
    $0.0.last == $0.1 ? $0.0 : $0.0 + [$0.1]
}.joined(separator: "\n")

edited Mar 16 '17 at 16:04

answered Mar 16 '17 at 15:56

Ashley Mills

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It works fine, thank you for this answer and the other comments. – Cue Mar 16 '17 at 16:09
I could have sworn that I wrote it that way but it didn't work - I guess I fat fingered it somewhere. – Ashley Mills Mar 16 '17 at 19:03

score 1 · Answer 2 · answered Mar 16 '17 at 16:39

You can use NSOrderedSet.

var str = "MacBook\nMacBook Pro\nMacPro\nMacBook\niMac\nMac mini\nMac mini"

var components = str.components(separatedBy: .newlines)
print(components)

let orderedSet = NSOrderedSet(array: components)
components = orderedSet.array as! [String]
print(components)

let newStr = components.joined(separator: "\n")
print(newStr)

score 0 · Answer 3 · answered Jun 24 '23 at 16:09

Swift 5 Update from @ashley-mills

let str = "MacBook\nMacBook Pro\nMacPro\nMacBook\niMac\nMac mini\nMac mini"
let components = str.components(separatedBy: .newlines)

let depDuped = components.reduce([]) {
    $0.contains($1) ? $0 : $0 + [$1]
}.joined(separator: "\n")

How to remove duplicates of lines of a String in Swift without lost their order?

3 Answers3