100 Days of SwiftUI Learning — Day 4

“For changes to be of any true value, they’ve got to be lasting and consistent.” - Tony Robbins.

Agenda

1. Type Annotations
2. Checkpoint 2

Type Annotations

Type annotations let us be explicit about what data type we want when declaring a variable or constant.

let variable_name: data_type = value

Here are the reasons why you use type annotations

1. Swift can’t figure out what type should be used.
2. You want swift to use a different type from its default type.
3. You don’t want to assign a value just yet.

Declaring just the data type of a variable or constant

Integer: let constant_name : Int

Double: let constant_name:Double

String: let constant_name: String

Bool: let constant_name: Bool

Array: let constant_name:[data_type]

Dictionary: let constant_name: [key_data_type : value_data_type]

Set: let constant_name: Set<data_type>

When you declare a constant using type annotation, swift won’t allow you to accidentally use that constant before assigning it a value. Once you assign the value, you cannot change it.

Checkpoint 2

Challenge

1. Create an array of strings with duplicates.
2. Print number of items in the array.
3. Get number of unique items in the array.

Solution

//Creating an array
let letters = ["a","b","c","a","d","b","e"]
//Number of items in the array
print(letters.count)
//Getting unique items of the array using set
let uniqueLetters = Set(letters)
//Number of unique items in the array
print(uniqueLetters.count)

There wasn’t a lot of content to study today. Take a break, reflect on what you have learned and come tomorrow to continue learning.

That is everything for today. See you tomorrow.