Intro to Swift 5

What is Swift?

“Swift is a general-purpose, multi-paradigm, compiled programming language developed by Apple Inc. for iOS, iPadOS, macOS, watchOS, tvOS, Linux, and z/OS. Swift is designed to work with Apple’s Cocoa and Cocoa Touch frameworks and the large body of existing Objective-C code written for Apple products” -

Type Safe

Swift performs type checks when compiling code and flags any mismatched types.
This encourages the developer to be intentional and clear with the types they declare for values. Once declared as a type, it cannot be changed.
In other words, while we can change the value of a variable, we cannot change its type.

var thisIsAString: String = "Cannot change to different type"
thisIsAString = 0
    error: cannot assign value of type 'Int' to type 'String'

Type Inference

Infers the type based on the value provided
If it quacks like a duck, walks like a duck, then it must be a duck
If there’s double quotes around a variable’s value, it assumes it’s a String.
If there are no quotes around a variable’s value, it assumes it’s a Double.

Compiled

The Swift compiler uses LLVM for optimization and binary generation.

Statically Typed

All types are known at compile time

Open Sourced

As of December 2015, Swift is open sourced!

Ranges

A range is a built-in Swift type which expresses a sequence of values between a start and an end value.

For example, 1…5 is a range, its values are: 1, 2, 3, 4, 5.

A Half Open Ranges are a sequence of values between a start and not inclusive of the end value, denoted by start..<end.

For example, 1..5 is a half open range. It’s values are: 1, 2, 3, 4.

Example:

To print all the numbers for the range: -3, -2, -1:

for i in -3..<0 {
    print(i)
}

However, the below does not work. XCode will error Could be postfix '...' and binary '-'

for i in -3...-1 {
    print(i)
}

Therefore, wrap the negative value in a parentheses ()

for i in -3...(-1) {
    print(i)
}

Repeat While

Repeat while guarantees that the body will execute at least oncel therefore the conditional is checked at the end of the loop. This is different from a while loop because in a while loop, it checks the conditional at the beginning of the loop, thus not guaranteeing that the body of the loop will be executed.

Structs

A struct is a useful way to group properties together to represent a common object
A struct is a value type, which means the values are copied. They are independent instances with its own unique copy of its data.
The properties in a struct cannot be modified within its instance methods by default
If a method mutates a property on a struct then use the mutating keyword before the function declaration

struct Employee {
    let name: String
    var age: Int
    var salary: Int
    var bonus: Int
}

mutating func setBonusMultiplier() {
    bonus *= 0.50
}

Computed Properties

Useful when a property value depends on another property’s value.
Computed Properties act like methods such that it can compute the value and return a value for that property

struct Employee {
    let name: String
    var age: Int
    var salary: Int {
        salary = salary + bonus(0.10)
    }
    var bonus: Int
}

mutating func setBonusMultiplier() {
    bonus *= 0.50
}

Enums

An enum is a useful way to declare types for a group of related values.
An enum is a value type, which means the values are copied. They are independent instances with its own unique copy of its data.
Defines a common type for a group of related values and enables you to work with those values in a type-safe way within your code.

enum Direction: String {
    case north = "north"
    case east = "east" 
    case west = "west"
    case south = "south
}

intro to swift 5