How to add element at Last index Swift

Question

I am getting an Array from server and I store it in NSMutableArray. Now the issue is that the Array is not sorted. For eg. array = ["A","B","None","C","D"]. I want to sort it and place the "None" element at last. i.e ["A","B","C","D","None"]. Tried swapping but was unable to match the condition, as the array may increase in future. Check my code below which is not working as expected.

if array.containsObject( "None" ){
        print("\(array.indexOfObject("None"))")
        let noneIndex = array.indexOfObject("None")
        print(noneIndex)
        array.removeObject(noneIndex)
        print("Remove Array:-\(array)")
        array.insertObject(noneIndex, atIndex: (array.lastObject?.index)!)
        print("Sorted Array:-\(array)")
    }

Is there any reason why you don't use the provided sort() or sorted() methods? — Losiowaty
– Losiowaty, Commented Dec 15, 2016 at 7:49

pbodsk · Accepted Answer · 2016-12-15 08:27:42Z

2

Maybe I'm misunderstanding what it is that you need to do, but you could use sorted() on your array if you just want to sort it alphabetically.

You could also use filter to remove "None" from your array, sort it, and then append "None" as the last element

For instance, if you have

let elements = ["Alpha", "Bold", "None", "charlie", "Delta", "echo", "zebra", "k"]

You could start out by filtering it:

let filteredElements = elements.filter { $0.uppercased() != "NONE"}

Sort the filtered elements:

var sortedElements = filteredElements.sorted { $0.uppercased() < $1.uppercased()}

Append "None"

sortedElements.append("None") // ["Alpha", "Bold", "charlie", "Delta", "echo", "k", "zebra", "None"]

And be done.

Here it is combined:

let lastElement = "None"
let elements = ["Alpha", "Bold", "None", "charlie", "Delta", "echo", "zebra", "k"]
var sortedElements = elements.filter({$0.uppercased() != lastElement.uppercased()}).sorted(by: {$0.uppercased() < $1.uppercased()})
sortedElements.append(lastElement)

Hope that helps you.

edited Dec 15, 2016 at 8:27

answered Dec 15, 2016 at 7:53

pbodsk

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10 Comments

iDeveloper Over a year ago

Its not just alphabets , it can be anything , like words, . Condition is "None" should be last everytime.

user28434'mstep Over a year ago

@iDeveloper, in sorted closure add condition that makes "None" always greatest value.

iDeveloper Over a year ago

@pbodsk this is not working, it says, Value of type 'Elememt'(Aka 'AnyObject') has no member 'uppercased'

pbodsk Over a year ago

Hmm, OK, that must be because your array is defined as containing AnyObject objects instead of Strings. How is your array defined?

pbodsk Over a year ago

And as @jpetric says in a comment to his answer, you should consider using a Swift array instead of NSMutableArray. You get the filter, map and sorted methods amongst other goodies :)

|

Twitter khuong291 · Accepted Answer · 2016-12-15 08:09:37Z

1

var array = ["A", "B", "None", "C", "D"]
if let noneIndex = array.index(of: "None") {
    array.remove(at: noneIndex)
    array.append("None")
}
print(array)

edited Dec 15, 2016 at 8:09

Twitter khuong291

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answered Dec 15, 2016 at 7:50

Bhavin Ramani

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1 Comment

Martin R Over a year ago

Note that you don't need the check if array.contains() if you write if let noneIndex = array.indexOf("None") {

Cristik · Accepted Answer · 2016-12-15 10:18:06Z

1

This should move None at the end of the array, and sort the other elements:

let ["A", "B", "None", "C", "D"]
array.sorted { $1 == "None" || $0 < $1 } // ["A", "B", "C", "D", "None"]

This simply takes benefits of the by argument that can be passed to the sort/sorted method from Array.

Edit @MartinR had a very strong point regarding the comparison predicate from this answer, which indeed doesn't offer a strong weak ordering. Sorting the array with a correct predicate would be along the lines of:

array.sorted { $0 == "None" ? false : $1 == "None" ? true : $0 < $1 }

edited Dec 15, 2016 at 10:18

answered Dec 15, 2016 at 8:04

Cristik

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5 Comments

Cristik Over a year ago

@MartinR thanks for the observation, corrected the code

Martin R Over a year ago

That might work, but now the comparator is not a "strict weak ordering" as required: "None" < "None"

Cristik Over a year ago

@MartinR, correct, instances of "None" will be moved around due to the fact that "None" < "None". We can be pedantic and address this, we gain a little speed, however with the cost of increasing the complexity of the closure.

Martin R Over a year ago

I don't think this is unnecessary pedantry. The sorted methods requires a strict weak ordering. If that prerequisite is not satisfied the behaviour is undefined.

Cristik Over a year ago

@MartinR, hmm... I missed the strict weak ordering part from the API docs, thanks for bringing that up. I updated the answer, hopefully now is a correct one :)

JPetric · Accepted Answer · 2016-12-15 08:07:30Z

0

This will work:

// starting test array
let array = ["B", "None", "C","P","None","A", "Q"]
var sorted = array.sorted { (str1, str2) -> Bool in
    return str1 < str2
}

sorted.forEach { str in
    if str == "None" {
        if let idx = sorted.index(of: str) {
            sorted.remove(at: idx)
            sorted.append(str)
        }
    }
}

// Sorted array is now ["A", "B", "C", "P", "Q", "None", "None"]

edited Dec 15, 2016 at 8:07

answered Dec 15, 2016 at 7:58

JPetric

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5 Comments

JPetric Over a year ago

I would suggest using Swift's array. It will be better in the long run.

iDeveloper Over a year ago

Sorted is not available in swit 3.

JPetric Over a year ago

You sure? Because I tried the example in Playground with Swift 3. If you copy this whole example in Playground it should work.

iDeveloper Over a year ago

XCode 8.1 Swift 3

JPetric Over a year ago

There should be array.sorted method in swift 3.

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