Swift - Arrays

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Arrays are used to store ordered lists of values of the same type. Swift puts strict checking which does not allow you to enter a wrong type in an array, even by mistake. If you assign a created array to a variable, then it is always mutable, which means you can change it by adding, removing, or changing its elements; but if you assign an array to a constant, then that array is immutable, and its size and contents cannot be changed. If you try to change it, then the compiler will throw an error.

An array can store duplicate values in different positions. Each element in the array has an index value starting from 0 so that we can access and modify them using that index.

Creating Arrays in Swift

We can create an array by specifying the type of the array explicitly.

Syntax

Following is the syntax for creating an array −

var someArray : [Type] = []

We can also create an array without specifying its type. In this case, the compiler will automatically get the type of the array based on the assigned value.

var someArray = [value1, value2, value3]

If you need to create an array with a single value (by repeating it), you can do so using the Array() initializer.

var someInts = Array(repeating: "Swift", count: 4)

Example

In the following example we are creating 3 different arrays using all the above discussed syntaxes −

import Foundation

// Defining an array by specifying the type
var arr1:[Int] = [11, 44, 55, 77, 88, 22]
print("Contents of arr1 :", arr1)

// Defining an array without specifying the type
var arr2 = [101, 404, 550, 770, 880, 222]
print("Contents of arr2 :", arr2)

// Defining an array with a single value 
var arr3 = Array(repeating: "Tutorialspoint", count: 3)
print("Contents of arr3 :", arr3)

Output

The above program produces the following result −

Contents of arr1 : [11, 44, 55, 77, 88, 22]
Contents of arr2 : [101, 404, 550, 770, 880, 222]
Contents of arr3 : ["Tutorialspoint", "Tutorialspoint", "Tutorialspoint"]

Modifying and Accessing Arrays in Swift

In an array, every element has its own index value starting from 0. So to retrieve a value from an array, pass the index of the value we want to retrieve within square brackets immediately after the name of the array in the subscript syntax.

Syntax

Following is the syntax for accessing and modifying array −

arrayName[indexValue]

Here, the index starts from 0 which means the first element can be accessed using the index as 0, the second element can be accessed using the index as 1 and so on.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [11, 44, 55, 77, 88, 22]

// Accessing the element present at index 3
// Using subscript syntax
print("Array element:", someArr[3])

Output

When the above code is compiled and executed, it produces the following result −

Array element: 77

Using subscript syntax, we can also modify the elements of the array by assigning new value to the existing index.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [11, 44, 55, 77, 88, 22]

// Modifying the array element present at index 3
// Using subscript syntax
someArr[3] = 33
print("Modified Array element:", someArr[3])

Output

When the above code is compiled and executed, it produces the following result −

Modified Array element: 33

Adding a New Element in an Array in Swift

We are allowed to add new elements to the existing array using the following methods.

Using append() Method

It adds a new element at the end of the specified array.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [43, 32, 11]

// Appending new element using append() method
someArr.append(34)
someArr.append(60)

print("Updated Array", someArr)

Output

When the above code is compiled and executed, it produces the following result −

Updated Array [43, 32, 11, 34, 60]

Using the addition assignment operator (+=)

We can also add a new item at the end of an array using the addition assignment operator.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [43, 32, 11]

// Adding new element using += operator 
someArr += [30]
someArr += [90]

print("Updated Array", someArr)

Output

When the above code is compiled and executed, it produces the following result −

Updated Array [43, 32, 11, 30, 90]

Iterating Over an Array in Swift

Iterating over an array is the fundamental and most commonly used operation in programming. It allows the developer to access and process individual elements of the specified array. In Swift, we can iterate over an array using the following methods −

Using for-in loop

We can use a for-in loop to iterate over the entire set of values in an array. It is the easiest and cleanest method to access and process each element of the given array sequentially.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [3, 56, 12, 4, 23, 5, 6, 7, 8]

print("Array Elements:")
// Iterating over the array using a for-in loop
for x in someArr{
   print(x)
}

Output

When the above code is compiled and executed, it produces the following result −

Array Elements:
3
56
12
4
23
5
6
7
8

Using the enumerated() function with for-in loop

We can also use the enumerated() function along with the for-in loop, it returns the index of the item along with its value.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [3, 56, 23, 34, 5, 78, 9]

print("Array Elements with their index value:")

// Iterating over the array using for-in loop along with enumerated() function
for (index, element) in someArr.enumerated() {
   print("Value at index = \(index) is \(element)")
}

Output

When the above code is compiled and executed, it produces the following result −

Array Elements with their index value:
Value at index = 0 is 3
Value at index = 1 is 56
Value at index = 2 is 23
Value at index = 3 is 34
Value at index = 4 is 5
Value at index = 5 is 78
Value at index = 6 is 9

Using while loop

We can also iterate over the element of the given array using a while loop. It provides explicit control over the iteration. It can be useful where a fine-grained control is required over the iteration.

Example

import Foundation

// Defining and initializing an array
var someArr:[Int] = [3, 56, 23, 34, 5, 78, 9]

print("Array Elements:")

var indexVal = 0

// Iterating over the array using while loop
while indexVal < someArr.count {
   print(someArr[indexVal])
   indexVal += 1
}

Output

When the above code is compiled and executed, it produces the following result −

Array Elements:
3
56
23
34
5
78
9

Using forEach() Function

Swift provides a pre-defined function named forEach() to iterate over the given array. It is useful to perform simple operations on the individual elements of the given array without iterating explicitly.

Example

import Foundation

// Defining and initializing an array
var someArr:[String] = ["Mona", "Pihu", "Mayank", "Sumit"]

print("Array Elements:")

// Iterating over the array using forEach() function
someArr.forEach { names in
   print(names)
}

Output

When the above code is compiled and executed, it produces the following result −

Array Elements:
Mona
Pihu
Mayank
Sumit

Adding Two Arrays in Swift

We can use the addition operator (+) to add two arrays of the same type which will yield a new array with a combination of values from the two arrays.

Syntax

Following is the syntax for adding two arrays −

var result = Array1 + Array2

Example

import Foundation

// Defining and initializing an array
var someArr1:[Int] = [11, 44, 55, 77, 88, 22]
var someArr2:[Int] = [10, 40, 50, 70, 80, 20]

// Adding two arrays of the same type
// Using + operator
var resultantArray = someArr1 + someArr2

print("Concatenated Array: ", resultantArray)

Output

When the above code is compiled and executed, it produces the following result −

Concatenated Array:  [11, 44, 55, 77, 88, 22, 10, 40, 50, 70, 80, 20]

The count Property in Swift

The count property is used to count the total number of elements present in the specified array.

Syntax

Following is the syntax of the count property −

Array.count

Example

import Foundation

// Defining and initializing arrays 
var someArr1:[Int] = [3, 56, 12, 4, 23, 5, 6, 7, 8]
var someArr2:[String] = ["Blue", "Black", "Green", "Yellow"]
var someArr3:[Int] = []

// Counting the total number of elements present
// in the given array
// Using count property
print("Total number of elements present in someArr1 = \(someArr1.count)")
print("Total number of elements present in someArr2 = \(someArr2.count)")
print("Total number of elements present in someArr3 = \(someArr3.count)")

Output

When the above code is compiled and executed, it produces the following result −

Total number of elements present in someArr1 = 9
Total number of elements present in someArr2 = 4
Total number of elements present in someArr3 = 0

The empty Property in Swift

The empty property is used to check whether the given array is empty or not. This property will return true if the given array is empty. If the given array contains some element, then this property will return false.

Syntax

Following is the syntax of the empty property −

array.isEmpty 

Example

import Foundation

// Defining and initializing arrays 
var someArr1:[Int] = [2, 5, 66, 44, 32, 2, 12]
var someArr2:[String] = ["Blue, Black"]
var someArr3:[Int] = []

// Checking if the given arrays are empty or not
// Using isEmpty property
print("Is someArr1 is empty? = \(someArr1.isEmpty)")
print("Is someArr2 is empty? = \(someArr2.isEmpty)")
print("Is someArr3 is empty? = \(someArr3.isEmpty)")

Output

When the above code is compiled and executed, it produces the following result −

Is someArr1 is empty? = false
Is someArr2 is empty? = false
Is someArr3 is empty? = true