Swift Set tutorial : Create , access, modify and iterating a Set

Set in Swift :

Previously we have discussed about arrays in swift. Similar to array, set is another collection data type in swift. The main difference is that the elements in a set are unordered and it contain only unique elements. In this tutorial, we will show you how to create a set and different set operations :

Creating a set :

Set is denoted as Set , where Element is the type of elements . We can create an empty set like below :

import UIKit

var name = Set()

print (name.count)

It will print ‘0’. We can also create a set directly with an array literal :

import UIKit

var days : Set = ["Monday","Tuesday","Wednesday"]

print (days)

It will print :

["Monday", "Tuesday", "Wednesday"]

Since all the values of the array are of same type, we can also declare the set without using the type :

import UIKit

var days : Set = ["Monday","Tuesday","Wednesday"]

print (days)

Output will be same as above.
What will be the output for the example below :

import UIKit

var days : Set = ["Monday","Tuesday","Wednesday","Monday"]

print (days)

Since set contains only unique elements, it will include only one ‘Monday’ instead of two :

["Tuesday", "Monday", "Wednesday"]

 

Accessing and Modifying a set :

Check if it is empty and get the count of a set :

To check if a set is empty or not in swift, ‘isEmpty’ is used. To get the total number of elements of a set, ‘.count’ is used.

import UIKit

var days : Set = ["Monday","Tuesday","Wednesday","Monday"]
var months = Set()

if(!days.isEmpty){
    print ("days is not empty and count is \(days.count)")
}

if(months.isEmpty){
    print ("months is empty")
}

It will give the following output :

days is not empty and count is 3
months is empty

Inserting and removing an element to swift set :

For inserting an element, ‘insert()’ is used and for deleting an element ‘remove()’ is used. We can also check if an item is in a set or not using ‘contain()’ method.

import UIKit

var days : Set = ["Monday","Tuesday","Wednesday"]
days.insert("Thrusday")
print ("days after inserted ",days)

days.remove("Monday")
print ("days after removed ",days)

if(days.contains("Tuesday")){
    print ("set days contain string \"Tuesday\"")
}

days.insert("Monday")
print ("added monday again ",days)

Output :

days after inserted  ["Tuesday", "Monday", "Wednesday", "Thrusday"]
days after removed  ["Tuesday", "Thrusday", "Wednesday"]
set days contain string "Tuesday"
added monday again  ["Tuesday", "Thrusday", "Wednesday", "Monday"]

Iterating a swift set :

To iterate through a set, we can use one for in loop similar to array. Also, before iterating, you can sort the set if you want.

import UIKit

var data : Set = ["Banana","Monkey","Apple","Cat"]

for item in data.sorted() {
    print (item)
}

Output :

Apple
Banana
Cat
Monkey

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