Day 1 is all about variables, constants, strings, and numbers.

The first piece of content is titled Why Swift?

Why swift?

• started in 2014, bypasses language cruft built up over time.
• makes it hard to write unsafe code
• Makes it easy to write code that is clear aun understandalbe
• Supports all the world’s languages out of the box

SwiftUI

• deals with drawing things on screen
• came into the world in 2019

No cruft or confusion, just power at your finger tips.

About this course

The course is set up to help people learn the material in an effective manner. The goal is also to remember what you’ve learned.

It doesn’t strive to teach all of Swift, just the parts that we may find most useful.

Designed to be a hands on experience. Relentlessly focused on trying it yourself.

How to follow along

Type the code out. Run it. See if it works.
Use the playground.

How to create variables and constants

variables are used to store data

• Variables:
  A variable’s value can vary and change over time.

import Cocoa

var greeting = "Hello playground"

// var means create a variable
// greeting is the descriptive name of the variable
// = does the assignment 
// "hello playground" is the initial value we are storing in the variable

// redefining the variable
var name = "Ted"
name = "Rebecca"
name = "Keeley"

• Constants
  A constant can not be changed after it is defined

let character = "Daphne"

// can not be changed
character = "Bill" // won't work

codingConvention

• Use camel-case
• Prefer constants over variables to prevent run time changes

Scored 6/6 on Variables
Scored 6/6 on Constants

How to create strings

Strings are created like any other variable/constant, but enclosed in double quotes.
Multi-line strings are enclosed with 3 double quotes at the beginning and end. They aren’t used very often.
To escape a string, you would use the back slash character \ before the character you are escaping.

Scored 12/12 on Strings

How to store whole numbers

Whole numbers are integer type. They are created the same way other variables are created minus the double quotes. instead of commas, we can use underscores.

instead of doing this:

let num = 1000000000

we can do

let num = 100_000_000

Whole numbers can also be defined as the result of a calculation:

let score = 10
let lowerScore = score - 2

compound assignment operators

We can increment a integer variable like this:

var counter = 10
counter = counter + 5

or we can do this:

// we use var because the value is changing...

var counter = 10
counter += 5
// or
counter -= 10
// or 
counter /= 2
// or 
counter *= 3

Integer methods

let number = 120
print(number.isMultiple(of: 3))

or

print(120.isMultiple(of: 3))

Scored 12/12 on Strings & Integers

How to decimal numbers

Decimal numbers are stored similar to integers. They have a floating point in the value.

Ex.

let num = 5.23

However this results in a double. Ex.

let num = 0.1 + 0.2
// "0.30000000000000004"

You can not mix int values and double values. It must be explicitly expressed.

let a = 1
let b = 2.0
let c = Double(a) + b

There is also the CGFloat type and they can be used alongside the Double type

Once Swift has decided what kind of data you are storing, its type can not be changed.

This works

var name = "a"
name = "b"

This does not and will result in an error

var name = "a"
name = 34

Type safety is important because as the application grows, it is extremely hard to keep the types of variables in context