What does @[ mean in objective C

Question

For example:

[[FlyoutTableViewController alloc] initWithViewControllers:@[@[firstNavigationController],@[secondNavigationController]]];

- (id)initWithViewControllers:(NSArray *)viewControllers

I know it's sending a NSArray of these view controllers to initWithViewControllers, but I want to know more about this way of creating arrays. What are the benifits, any potential issues etc?

Also, do the objects, firstNavigationController and secondNavigationController need to be inside the @[ too, or what's going on there?

TIA

score 0 · Answer 1 · answered Jan 12 '14 at 17:55

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@[item1, item2, item3] is syntax sugar for [NSArray arrayWithObjects:item1, item2, item3, nil]. Nothing more than a shorthand. There are no more benefits or issues than with the method it expands to.

You can make arrays of arrays too like that. @[@[item1]] is an array containing a single array containing item1.

answered Jan 12 '14 at 17:55

zneak

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Well, to be precise, it is equivalent to `+[NSArray arrayWithObjects:count:]`, compare e.g. http://stackoverflow.com/questions/14527489/using-array-of-items-vs-nsarray-arraywithobjects. – Martin R Jan 12 '14 at 18:10

score 0 · Answer 2 · answered Jan 12 '14 at 17:55

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It means you are defining an array with a values. e.g.

@[value1, value2, value3]

answered Jan 12 '14 at 17:55

Inder Kumar Rathore

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score 0 · Answer 3 · answered Jan 12 '14 at 17:56

It's an array literal. Like a string literal @"My String". A shorthand notation for creating arrays. Similar usage and limitations to the NSString version (immutable).

So, @[firstNavigationController] creates an NSArray with a single item in it. And your parameter is an array of arrays.

score 0 · Accepted Answer · answered Jan 12 '14 at 17:56

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It is a shorthand way of creating an NSArray.

NSArray *array = [[NSArray alloc] init];

is equivalent to

NSArray *array = @[];

You can see more objective-c literals here.

answered Jan 12 '14 at 17:56

Connor Pearson

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mostruash · Answer 5 · 2014-01-12T21:00:04.827

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Let me give you the analogy.

"A String" : C-string

@"A String": Obj-C string (NSString)

{1,2} (not [1,2]): C array

@[@1, @2] (not @[1,2]): Obj-C array (NSArray with NSNumber elements)

edited Jan 12 '14 at 21:00

answered Jan 12 '14 at 17:56

mostruash

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Only problem is that ints can't be in an NSArray. Put @s in front of the integers to wrap them. – erdekhayser Jan 12 '14 at 17:58
True, though I'll keep the answer as it is so people can see your comment :) – mostruash Jan 12 '14 at 18:00
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The syntax for a C array is `{1, 2}` -- curly braces, not square. `[1,2]` is invalid. – jscs Jan 12 '14 at 20:07

What does @[ mean in objective C

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