How to initialize an empty mutable array in Objective C

Question

I have a list of objects (trucks) with various attributes that populate a tableview. When you tap them they go to an individual truck page. There is an add button which will add them to the favorite list in another tableview. How do I initialize an empty mutable array in Cocoa?

I have the following code:

-(IBAction)addTruckToFavorites:(id)sender:(FavoritesViewController *)controller
{
    [controller.listOfTrucks addObject: ((Truck_Tracker_AppAppDelegate *)[UIApplication sharedApplication].delegate).selectedTruck];

}

Solution 1

Update:

With new syntax you can use:

NSMutableArray *myArray = [NSMutableArray new];

Original answer:

for example:

NSMutableArray *myArray = [[NSMutableArray alloc] init];

And here you find out why (difference between class and instance method)

Solution 2

Basically, there are three options:

First

NSMutableArray *myMutableArray = [[NSMutableArray alloc] init];

Second

NSMutableArray *myMutableArray = [NSMutableArray new];

Third

NSMutableArray *myMutableArray = [NSMutableArray array];

Solution 3

You can also initialize in this way

Another way for Objective C apart from the answer of @NSSam

NSMutableArray *myMutableArray = [@[] mutableCopy];

For Swift

let myArray = NSMutableArray()

OR

let myArray = [].mutableCopy() as! NSMutableArray;

Solution 4

NSMutableArray *arr = [NSMutableArray array];

Solution 5

I use this way to initialize an empty mutable array in Objective C:

NSMutableArray * array = [NSMutableArray arrayWithCapacity:0];

View more solutions

Comments

[Nico]

Even if the array is initially empty, if you know that you will be putting a certain number of objects into it, initWithCapacity: may make that population step faster (because the array may initially create its backing storage with space for that many objects).

[Nico]

Moreover, autorelease is not the evil that some people make it out to be. There's nothing wrong with [NSMutableArray array]; it's just not appropriate for this case, assuming that the controller will assign the new array directly to its private _listOfTrucks instance variable.

[saagarjha]

This doesn't create a mutable array.