in Swift: Difference between Array VS NSArray VS [AnyObject]

Array is a struct, therefore it is a value type in Swift.NSArray is an immutable Objective C class, therefore it is a reference type in Swift and it is bridged to Array<AnyObject>.NSMutableArray is the mutable subclass of NSArray.

var arr : NSMutableArray = ["Pencil", "Eraser", "Notebook"]var barr = ["Pencil", "Eraser", "Notebook"]func foo (var a : Array<String>){    a[2] = "Pen"}func bar (a : NSMutableArray){    a[2] = "Pen"}foo(barr)bar(arr)println (arr)println (barr)

Prints:

(    Pencil,    Eraser,    Pen)[Pencil, Eraser, Notebook]

Because foo changes the local value of a and bar changes the reference.It will also work if you do let arr instead of var as with other reference types.

Array is a Swift construct, and generic struct, which means that it can be an array of any specific type (Int, String, AnyObject, etc.)

[T] is syntactic sugar for Array<T>

AnyObject is an object of any class, including Objective-C classes.

NSArray is an Objective-C construct that can hold any Objective-C object and is transparently mapped to and from Array<AnyObject>

Using the Krzak answer, here is a practical example:

// Let´s create an Array as a struct showing alternative ways    var arrStruct = ["Pencil", "Eraser", "Notebook"]    // or var arrStruct: [String] = ["Pencil", "Eraser", "Notebook"]    // or var arrStruct: Array = ["Pencil", "Eraser", "Notebook"]    // or var arrStruct = Array(["Pencil", "Eraser", "Notebook"])    // All this alternative ways create an array as struct    // Now let´s create a function that modifies this array struct    func modifyArr(alternativeArr: [String])     // or func modify(alternativeArr: Array<String>)    {        alternativeArr[2] = "Pen" // compilation error        // This won´t work. In swift >= 3.0 all func parametes are a let variable,         // this means alternativeArr is defined as a let. What one has to do is         // create a local variable and copy the value.        var localAlternativeArr = alternativeArr        // or var localAlternativeArr: [String] = alternativeArr        // or var localAlternativeArr: Array = alternativeArr        // now we can change it.        localAlternativeArr[2] = "Pen"        print(localAlternativeArr) // ["Pencil", "Eraser", "Pen"]        print(alternativeArr) // ["Pencil", "Eraser", "Notebook"]    }    modifyArr(alternativeArr: arrStruct)    print(arrStruct) // ["Pencil", "Eraser", "Notebook"]    // Since the arrStruct is a struct every time we assign to another variable or     // pass it as a func argument a copy is made.// Now let´s create as an NSMutableArray    var arrClass: NSMutableArray = ["Pencil", "Eraser", "Notebook"]    // or var arrStruct = NSMutableArray(array: ["Pencil", "Eraser", "Notebook"])    // All this create an NSMutableArray as a class    // Now let´s create a function that modifies this array struct    func modifyArr(alternativeArr: NSMutableArray)    {        alternativeArr[2] = "Pen"        print(alternativeArr)        // (        //   Pencil,        //   Eraser,        //   Pen        // )    }    modifyArr(alternativeArr: arrClass)    print(arrClass)    // (    //   Pencil,    //   Eraser,    //   Pen    // )    // Since the arrClass is a class everytime we assign to another variable or     // pass it as a func argument is passed by reference. Means that any change    // inside modifyArr is going to change the arrClass outside. The change     // is made in the same pointer.