addObject to NSArray in Objective-C

Question

How to addObject to NSArray using this code? I got this error message when trying to do it.

NSArray *shoppingList = @[@"Eggs", @"Milk"];
NSString *flour = @"Flour";
[shoppingList addObject:flour];
shoppingList += @["Baking Powder"]

Error message

/Users/xxxxx/Documents/iOS/xxxxx/main.m:54:23: No visible @interface for 'NSArray' declares the selector 'addObject:'

possible duplicate of [NSArray adding elements](http://stackoverflow.com/questions/778465/nsarray-adding-elements) — Benjamin Jimenez, Jun 25 '15 at 21:12
NSMutableArray *imageArray; imageArray =[[NSMutableArray alloc]init]; [imageArray addObject:imagename]; — Ramani Hitesh, Sep 19 '17 at 10:19

score 19 · Accepted Answer · answered Jun 25 '15 at 18:34

addObject works on NSMutableArray, not on NSArray, which is immutable.

If you have control over the array that you create, make shoppingList NSMutableArray:

NSMutableArray *shoppingList = [@[@"Eggs", @"Milk"] mutableCopy];
[shoppingList addObject:flour]; // Works with NSMutableArray

Otherwise, use less efficient

shoppingList = [shoppingList arrayByAddingObject:flour]; // Makes a copy

score 4 · Answer 2 · answered Jun 25 '15 at 18:33

4

You can't add objects into NSArray. Use NSMutableArray instead :)

answered Jun 25 '15 at 18:33

marhs08

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Claudio Redi · Answer 3 · 2015-06-25T19:13:01.890

2

Your array cant be changed because is defined as NSArray which is inmutable (you can't add or remove elements) Convert it to a NSMutableArray using this

NSMutableArray *mutableShoppingList = [NSMutableArray  arrayWithArray:shoppingList];

Then you can do

[mutableShoppingList addObject:flour];

edited Jun 25 '15 at 19:13

answered Jun 25 '15 at 18:33

Claudio Redi

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Um, `[NSMutableArray shoppingList]`? Looks like your code is missing something. – jlehr Jun 25 '15 at 18:42

score 1 · Answer 4 · answered Jun 25 '15 at 18:43

NSArray does not have addObject: method, for this you have to use NSMutableArray. NSMutableArray is used to create dynamic array.

NSArray *shoppingList = @[@"Eggs", @"Milk"];
NSString *flour = @"Flour";

NSMutableArray *mutableShoppingList = [NSMutableArray arrayWithArray: shoppingList];
[mutableShoppingList addObject:flour];

Or

NSMutableArray *shoppingList = [NSMutableArray arrayWithObjects:@"Eggs", @"Milk",nil];
NSString *flour = @"Flour";
[shoppingList addObject:flour];

addObject to NSArray in Objective-C

4 Answers4