Containers

Objective-C has the same exact core containers that Swift does, with the two exceptions being that they are named slightly differently, and all of the containers in Objective-C are reference types because of the basic requirement that all Objective-C types must be reference types.

Arrays

In Objective-C arrays are called NSArray. Let's take a look at the initialization of an array in both Swift and Objective-C side-by-side:

var array = [Int]()
NSArray *array = [NSArray alloc];
array = [array init];

We have defined a variable called array that is a reference to the type NSArray. We then assign it to a newly allocated instance of NSArray. The square bracket notation in Objective-C allows us to call methods on a type or on an instance. Each separate call is always contained within a single set of square brackets. In this case, we are first calling the alloc method on the NSArray class. This returns a newly allocated variable that is of the type NSArray.

In contrast to Swift, Objective...