How to add string objects to NSMutableArray

Question

I have an NSMutableArray named randomSelection:

NSMutableArray *randomSelection;

I am then trying to add strings to this array if certain criteria are met:

[randomSelection addObject:@"string1"];

I am then trying to output the string, to determine if it has added it:

NSString *test = [randomSelection objectAtIndex:0];
NSLog(test);

However nothing is being output to the error log and I can't figure out why.

Any help/hints appreciated.

Are you sure that the certain critera to add the string are met? Otherwise, maybe you should try NSLog(@"%@", test); — David Brunow
– David Brunow, Commented Dec 12, 2012 at 6:56
Yes the criteria is met. Just below NSLog(test) i have placed: NSLog("Made It!"); and that is being displayed. — SamBo
– SamBo, Commented Dec 12, 2012 at 7:00
do i need to initialise the NSMutable array and alocate with ample space or something? I thought that was the point of this addObject function so that i dont have to do that. — SamBo
– SamBo, Commented Dec 12, 2012 at 7:01
@David Brunow Please read question before putting any comments or ans.... this guy had not allocate "NSMutableArray *randomSelection;", so how he expect to get array object.... — Sunil Targe
– Sunil Targe, Commented Dec 12, 2012 at 7:24

hp iOS Coder · Accepted Answer · 2012-12-12 07:00:58Z

68

I think you are missing to allocate the memory for array. So try this

NSMutableArray *randomSelection = [[NSMutableArray alloc] init];
[randomSelection addObject:@"string1"];
NSString *test = [randomSelection objectAtIndex:0];
NSLog(test);

answered Dec 12, 2012 at 7:00

hp iOS Coder

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2 Comments

ophychius Over a year ago

@SamBo did indeed forget to allocate memory and initialize it. Right now the Array gets declared, but not defined.

Lehlohonolo_Isaac Over a year ago

@ophychius Also had the same problem. At least now I know that I need to allocate memory for the array first. But isn't there a more generic way to specify that you only want to add strings in the array?

Pratik Mistry · Accepted Answer · 2013-02-26 13:13:31Z

5

NSMutableArray *randomSelection =  [[NSMutableArray alloc]init];
[randomSelection addObject:@"string1"];

You need to alloc it first.

edited Feb 26, 2013 at 13:13

answered Dec 12, 2012 at 7:01

Pratik Mistry

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Comments

Girish · Accepted Answer · 2012-12-12 07:14:51Z

2

First allocate the array using following statement & then objects in it.

NSMutableArray *randomSelection =  [[NSMutableArray alloc] init];
[randomSelection addObject:[NSString stringWithFormat:@"String1"]];
[randomSelection addObject:[NSString stringWithFormat:@"String2"]];
NSLog(@"Array - %@", randomSelection);

This will definitely solves your problem.

answered Dec 12, 2012 at 7:14

Girish

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Comments

Sunil Targe · Accepted Answer · 2012-12-12 07:29:36Z

1

Just allocate your NSMutableArray. You'll get solved your problem.

answered Dec 12, 2012 at 7:29

Sunil Targe

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Comments

Anusha Kottiyal · Accepted Answer · 2012-12-12 08:01:15Z

1

Try this:

NSMutableArray *randomSelection = [[NSMutableArray alloc]init]; 
[randomSelection addObject:@"string1"];

edited Dec 12, 2012 at 8:01

Anusha Kottiyal

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answered Dec 12, 2012 at 7:20

Rahul Gupta

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Comments

Alvin George · Accepted Answer · 2016-02-11 07:58:19Z

0

Swift :

var randomSelection: [AnyObject] = [AnyObject]()
randomSelection.append("string1")
let test: String = randomSelection[0] as! String
print(test)

OR

let array : NSMutableArray = []
array.addObject("test String")
print(array)

answered Feb 11, 2016 at 7:58

Alvin George

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