How to create and populate structure like below by using for loop? ObjectiveC

Question

** Could somebody help me to understand this type of initialization? It seems to me that this part of code:

"username: @"Johny" look like nsdictionary initializationa object for key?**

 NSArray *items = @[@{@"username": @"Johny",
                    @"userpic": @"Photo.png",
                     @"image": @"photo1.jpg"},

                   @{@"username": @"George",
                     @"userpic": @"Photo.png",
                     @"image": @"photo2.jpg"},

                   @{@"username": @"Mandy",
                     @"userpic": @"Photo.png",
                     @"image": @"photo3.jpg"},

                   @{@"username": @"Jacob",
                     @"userpic": @"Photo.png",
                     @"image": @"photo4.jpg"},

                   @{@"username": @"Brandon",
                     @"userpic": @"Photo.png",
                     @"image": @"photo5.jpg"},

                   @{@"username": @"Dave",
                     @"userpic": @"Photo.png",
                     @"image": @"photo6.jpg"}
                   ];

*in my code i'm getting all values by using for loop *

for (NSDictionary *dictionary in items) {
{
    //

}

Answer 1

There were some changes introduced to Objective-C by Apple at the 2012 WWDC. If you have not seen the WWDC 2012 video Modern Objective-C then I would highly recommend you viewing that video which explains the changes introduced. Amongst those changes added were Array Literals and Dictionary Literals

Basically just like you can create a String Literal by creating the following:

NSString *name = @"Slim Shady"

Apple introduced Array Literals and Dictionary Literals too Following examples are from the Video

Where initially to create an Array the options were:

NSArray *myArray; 
myArray = [NSArray array];  // an empty Array
myArray = [NSArray arrayWithObject:anObject];  // an array with a single object
myArray = [NSArray arrayWithObjects: a, b, n, nil];  // array with 3 objects a, b, c

Array Literals allows you to create an Array in the following ways:

myArray = @[ ];   // an empty Array
myArray = @[anObject];  // array with a single object
myArray = @[a, b, c];  // array with 3 objects a, b, c 

as you can see using the Literals it is clearer and easier to create the Array. Similarly for NSDictionary Where initially the options to create a Dictionary were:

NSDictionary *myDict; 
myDict = [NSDictionary dictionary]; // empty Dcitionary
myDict = [NSDictionary dictionaryWithObject:object forKey:key]; 
myDict = [NSDictionary dictionaryWithObjectsAndKeys: object1, key1, object2, key2, nil];

Dictionary Literals allow you to create the dictionary in the following ways:

myDict = @{ }; // empty ditionary
myDict = @{ key:object }; // notice the order of the key first -> key : object
myDict = @{ key1:object1 , key2:object2 }; 

Answer 2

It's an array of dictionary objects using the new(ish) Objective-C literals syntax.

As well as the traditional literal strings, which we all know and love: @"Hello World", there are:

• NSArray literals: @[ element1, element2 ], which has the advantage of not needing a trailing nil like [NSArray arrayWithObjects:] does.
• NSDictionary literals: @{ key : value, key : value }, which has the advantage of being more natural in the key-value order compared to [NSDictionary dictionaryWithObjects:forKeys:].
• NSNumber literals: @(YES) (boolean), @(1.2) (floating point), @(123) (integer).

and they all have the advantage of being much more concise and natural.

Answer 3

In iOS 6, Apple created a new way of initialising NSArray and that's what is the case here.

It functions just like the arrayWithObjects functions, just that the syntax is a little different.

Your NSArray is filled with NSDictionary objects.