Chasen’s Swift Blog

Day 15 is a review of the last two weeks of material! #100DaysOfSwiftUI

I kept on going back to the individual pages to find the syntax I needed while working on the tests, so I’m happy to have it all on one page: www.hackingwithswift.com/articles/…

Day 14 is optionals, guards, nil coalescing, optional chaining, and optional try.

Guards are new to me but I like them:

func double(number: Int?) -> Int? {
	guard let number = number else {
		return nil
	}
	return number * 2
}

Two weeks in the books! #100DaysOfSwiftUI

Prototypes, opaque return types, extensions, and protocol extensions don’t have equivalents in JavaScript (and my TypeScript isn’t good enough to compare Swift to TS), but these concepts were straightforward enough that I breezed through day 13. #100DaysOfSwiftUI

copies of the same class share their underlying data, meaning that changing one changes them all, whereas structs always have their own unique data, and changing a copy does not affect the others.

I found this explanation confusing until I took the test and realized the difference.

In JS, creating an object or class instance and assigning it to two different variables matches the “copy” semantics above (the variable is a reference to the object).

The “struct” behavior (by value) is how primitives work in JS (string, bool, etc.). Objects never work this way.

Day 12 over! #100DaysOfSwiftUI

Structs (part two) with a checkpoint… day 11 was pretty straightforward! #100DaysOfSwiftUI

Structs, mutating on methods, computed properties, property observers, custom initializers… it’s a lot but it was pretty easy to get through.

I think the only “new” concept (coming from JavaScript) was marking methods as mutating.

Day 10 done so 10% of the way there! #100DaysOfSwiftUI

Dropping the parenthesis when calling functions with a closure blows my mind:

team.filter { $0.hasPrefix("T") }

The equivalent in JS:

team.filter($0 => $0.startsWith("T"))

Woo! The checkpoint test actually didn’t take me very long to complete.

Day 9 in the books! #100DaysOfSwiftUI

Really interesting that Swift has do, but it’s not what you think!

do {
    try throwingFunction1()
    nonThrowingFunction1()
} catch {
    print("Handle errors here")
}

In JS, that do would be try and no “try” is required before a throwing function.

Day 8 in the books! #100DaysOfSwiftUI

Awesome to me that this is valid:

func record(age: Int) { }
func record(year: Int) { }

Naming internal and external parameters separately is interesting too:

func square(of num: Int) -> Int {
    return num * num
}

let result = square(of: 4)

Day 7 in the books! #100DaysOfSwiftUI

Day 6 is all about for and while loops.

I’ll be excited to learn the .map and .filter equivalents. I rarely use for loops in JS and have only used while a couple times in my career. 🫢

I wasn’t expecting to do FizzBuzz for the checkpoint test. There’s a first time for everything! #100DaysOfSwiftUI

No === in Swift (just ==) is nice!

Enums being comparable is pretty cool too.

And switch statements… is this the day I confess that I tend not to use them in JavaScript? Swift’s fallthrough syntax seems much safer than JS needing a break for each case.

Day 5 done! #100DaysOfSwiftUI

This is really interesting:

let name: String
// …
name = "Chasen"
// Allowed once

In JavaScript, the “equivalent” (using const) requires an initial value and doesn’t let you reassign it later. I like that Swift allows it be undefined and assigned just once.

Day 4 done! #100DaysOfSwiftUI

Coming from JS, there are some small differences in array and dictionary syntax. This really stood out to me (as nice and explicit):

let olympics = [
    2016: "Rio de Janeiro",
    2021: "Tokyo",
    2024: "Paris"
]

print(olympics[2020, default: "Unknown"])

Day 3 in the books! #100DaysOfSwiftUI

This has a bug… can you spot it?

let temperature = 29
let converted = (temperature * 9 / 5) + 32
print("Celsius: \(temperature)")
print("Fahrenheit: \(converted)")

I thought the compiler might warn when losing precision like this, but I guess not!

Day 2 in the books! #100DaysOfSwiftUI

Is it cheating to do Day 1 on the same day as Day 0? 🙈 #100DaysOfSwiftUI