Convert NSArray to NSMutableArray Swift

Question

I'm trying to convert a the self.assets NSArray to NSMutableArray and add it to picker.selectedAssets which is a NSMutableArray. How will this code look like in swift?

Objective-C Code

picker.selectedAssets = [NSMutableArray arrayWithArray:self.assets];

Without bothering to look at the docs, I imagine NSMutableArray(self.assets) and/or NSMutableArray.arrayWithArray(self.assets) would do it. — Kevin
– Kevin, Commented Sep 17, 2014 at 21:25

Imanou Petit · Accepted Answer · 2019-04-26 20:35:50Z

29

With Swift 5, NSMutableArray has an initializer init(array:) that it inherits from NSArray. init(array:) has the following declaration:

convenience init(array anArray: NSArray)

Initializes a newly allocated array by placing in it the objects contained in a given array.

The following Playground sample code shows hot to create an instance of NSMutableArray from an instance of NSArray:

import Foundation

let nsArray = [12, 14, 16] as NSArray
let nsMutableArray = NSMutableArray(array: nsArray)
nsMutableArray.add(20)
print(nsMutableArray)

/*
prints:
(
    12,
    14,
    16,
    20
)
*/

edited Apr 26, 2019 at 20:35

answered Sep 17, 2014 at 21:34

Imanou Petit

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5 Comments

Peter Pik Over a year ago

imagePicker.selectedAssets = NSMutableArray(array: self.assets!) Returns: fatal error: unexpectedly found nil while unwrapping an Optional value

Imanou Petit Over a year ago

By reading your comment, I guess that self.assets is in fact of type NSArray?. If so, you should perform an optional binding before assigning it to your NSMutableArray.

Peter Pik Over a year ago

optional binding could i explain?

Imanou Petit Over a year ago

Have a look here then try the following code: if assets = self.assets {picker.selectedAssets = NSMutableArray(array: assets)}.

Taoufik Over a year ago

This line is such a beauty , "let nsMutableArray = NSMutableArray(array: nsArray)" , simple but effective ; thank you sir for this answer

Connor · Accepted Answer · 2014-09-17 21:34:33Z

3

You can do the same thing in swift, just modify the syntax a bit:

var arr = NSArray()
var mutableArr = NSMutableArray(array: arr)

answered Sep 17, 2014 at 21:34

Connor

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2 Comments

mc01 Over a year ago

Should it be let arr?

Connor Over a year ago

it could also be let. Since both arrays are only initialized in the snippet, they could both use let. It depends on how you use them after

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