Arrays or Lists Tutorial With Examples in iOS using Swift 4 - Collection Types

We mostly use Arrays and Dictionaries while developing apps. Sets also we will use but not as much as Arrays and Dictionaries.

In this tutorial we dive into Arrays using Swift 4. We are going to use Playgrounds for learning Arrays.

Arrays:

An Array is a list of ordered values of the same type. Array may contain same value at different indexes.

5 Ways To Concatenate/Merge Two Arrays into One Array in Swift 4

 

Sorting Arrays in Swift

Initialization :

In swift arrays initialization like below. Copy and paste in Playground.

var userIds = Array()
print("userIds is of type [Int] with \(userIds.count) items.")

Output: userIds is of type [Int] with 0 items.

'userIds' is an Empty Array of type Int.  

     How to Create Empty Array ?

      We can create empty array using following line.

var emptyArray = [Any]()

       Any may be Int, Float, Double, String etc...

 

Adding/Inserting elements to Array :

In swift for adding elements to Array we use Append().

userIds.append(1)

userIds.append(3)

print(userIds)

Output: [1, 3]

userIds now contains 2 value of type Int

For getting the elements count from Array use 'count'.

print(userIds.count)

Great. By using Append element is adding to array at end. If we want to add at a particular index append won't work.

No worries it's easy.

Now for adding at starting we using 'insert'.

userIds.insert(20, at: 0)

print(userIds)

Output: [20, 1, 3]

We can add any element at any index between 0 to userIds.count.

Adding at second position follows as below.

userIds.insert(45, at: 1)

print(userIds)

Output: [20, 45, 1, 3]

Note: Index starts from 0. second position means index = 1.

Make userIds Array empty. So simply write following code.

userIds = []

print(userIds)

Output: [20, 45, 1, 3]

Array With Default Values:

create simple array with default values.

var defaultArray = [2, 4, 6, 8]

For adding same element multiple times swift made easy function.

var threeDoubles = Array(repeating: 0.0, count: 3)
// threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0]

Creating an Array By Adding Two Arrays Together:

In swift we can create an array by adding two compatable arrays using an additional operator (+).

The new created array type is inferred from type of two arrays you add together.

var anotherThreeDoubles = Array(repeating: 2.5, count: 3)
// anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5]
 
var sixDoubles = threeDoubles + anotherThreeDoubles
// sixDoubles is inferred as [Double], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.5]

There are more we can do with Arrays. We will cover later.

Modifying & Accessing Arrays:

Subscripts :

We can modify or access arrays using Subscripts.

var whishList = ["juice", "biscuits", "fruits", "vegetables"] // Create array with string literals

Suppose we want to access first element simply we can use subscript as follow.

var firstItem = whishList[0]

To modify a element in an array we can use subscripts.

Modify second item with 'chocolates' as follow.

whishList[1] = "chocolates"

// the second item in the list is now equal to "chocolates" rather than "biscuits" var firstItem = whishList[0]

Using Array Methods And Properties :

We use array method to remove object from an array.

whishList.removeFirst()

// the first item in the array has just been removed
// whishList now contains 3 items, and no juice

We can remove from a specific index also.

whishList.remove(at: 1)

// the item at index 1 has just been removed
// now whishList contains only 2 item

We can insert an elemnt to an array as follow.

whishList.insert("milk", at: 0)

// whishList now contains 3 items
// "milk" is now the first item in the list

Iterate/Loop Over an Array :

We can get all values from an array by simply iterating over it using for-in loop.

for item in whishList {
    print(item)
}

// milk
// fruits
// vegetables

We can use old method also with index but not efficient.

For getting index we use a different method called enumerated(). Iterate using this method we will get both index and value. It's a great features and efficient for getting two things for single execution.

for (index, value) in whishList.enumerated() {
    print("item\(index+1): \(value)")
}

// Item 1: milk
// Item 2: fruits
// Item 3: vegetables

Summary:

What we learnt from this article.

1. An array is a collection of elements of same type in a sequential order.
2. Elements order won't change by itself.
3. Initializing an array using different methods.
4. Adding elements to an array using append() function.
5. Inserting an element using insert(at:) function.
6. Adding two array using additional operator (+) will give an New Array.
7. We can modify and access array items using subscripts.
8. In array index starts from 0.
9. Deleting or Removing item from array using Remove(at:) function.
10. Iterating over an array using for-in loops.