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Show HN: Learn Swift (aidanf.net)
238 points by aidanf on June 9, 2015 | hide | past | favorite | 55 comments

I've been learning Swift in recent months, and as part of that process I wrote a short book about the language.

It's aimed at developers (like me) who can already program in a language like Ruby or Python and are looking for a quick tour of Swift.

It's available to read for free online at http://books.aidanf.net/learn-swift

I'll be adding stuff about yesterdays announcements in the next couple of weeks.

Great timing on the post. I'm a Python(2) user who is always on the lookout for the next language to jump to since I'm never moving to Python3. With Swift on the server and iOS, and being a very pleasing language similar to Python, this will be what I study next as I look to migrate off Python2 as it dies (which itself may take a while). Thanks for posting this.

Out of curiosity, why are you avoiding Py3? I've not touched python in a couple years. I was thinking of taking it back up, just to be more familiar with it.

As the other guy who replied said, there's nothing explicitly wrong with it. But it's not to be ornery. I think it only appears that way to people who haven't thought it through. I don't owe GVR or the core dev team anything. Certainly not thousands of man-hours to make their new, unnecessarily breaking version of Python3 to be successful. It's that going from Python2, it's mere technical churn. Python3 has zero technical innovation. It's just a different way of doing certain things, nothing more. Unicode was supported in Python since 2.6. Print was a statement rather than a function. Std lib cleanups. So what? Bigger fish to fry in the world than that. All of the new features, can, and do work on Python2 in the form of backports.

It breaks everything I've ever written, for no good reason. I also end up with a much smaller pool of libraries to choose from for new projects.

It makes no sense. In a microcosm of the universe where Python was the only game in town, Python3 would have worked out. Instead of moving to 3 and losing many advantages for churn, I can just go spend time with something else. Swift is pretty what I'd design if I could pick and choose features, so it's perfect for me- excited I'll be able to use it serverside while simultaneously learning the language for iOS.

Also, people frequently cite that moving from 2->3 is easy. It is. But they somehow forget that testing old, large projects is extremely labor intensive and always results in breakage. Unless you have 100% test coverage, which I know no one who does.

Interesting points, I'll keep them in mind. I don't really have to worry too much about making old code work, so I'd not be too concerned with that. I'll probably start with Py3 because I don't really expect to rely on too much library support for the things I'd cobble together in python.

As far as unit testing goes, you are absolutely right. I unit test everything....I mean, I was taught TDD right out of the door at Uni, and though I don't exactly follow the methods strictly, I am at my core, a functional programmer. I want every last bit of code I write to do one and only one thing well. I, therefore, test all of those functions, no matter how mundane. But you know what? Even then, my test coverage on a good project, where I'm not just dicking around probably hovers about 85-95% coverage. There's just always some flotsam and jetsam that escapes the tests. First time I worked on a project with a team, I stressed my head off because of that very fact, until we did our first metrics review and I saw that I was actually ahead of most people....

And also, you'll find more bugs in Python3 libraries. They're being used less than Python2 libs. That, and the long tail of libraries that may never get moved to Python3. There's really a lot of reasons to not use 3, or like me, wait to see if it ever really overtakes 2. A 3rd extra reason if you needed any more, is that almost all jobs in the field use 2.x. I tried to love Python3, but the technical reasons just don't make sense to migrate, and once you meet the coercion and vitriol of the Python3 community, you'll learn to resent its existence and them.

The future of Python2 is actually very bright, while 3's is in jeopardy. That's why everyone is so pushy about it, they lose their bet if it never gets over the hump. Being as 3.0 was released in 2008 and it's now 2015, I honestly think that answer is already here.

Using 2, then switching to 3 if it ever does overtake it makes a lot of sense and is the sensible bet. But 3.x overtaking 2 anytime soon is really unlikely, and library worth anything will be 2+3 compatible and dropping 2 support would just be asinine with the ~83% userbase it holds today.

Even if Python3's userbase doubles in 5 years, it'll still be under 50% of the overall Python userbase. And I think doubling its current usage would be overly optimistic. Python3 will either collapse, or split the community (already has to a degree) with someone forking Python2 for good. Pyston may be that fork, or a couple other contenders.

The situation is a disaster all around. For Python and the community. Companies in some cases now aren't putting new product down in Python because of this. You'll be alright using 3, because no matter the final outcome you'll be able to go back to 2 without issues and vice versa. I only recommend 2 because you won't be missing any libraries if you use it, and if you want to do it for a job you'll be using 2.x anyway.

Python3's biggest purpose is giving people a reason to hassle maintainers to port to it. They bite on the political propaganda surrounding 3, that it's the "newest version", which for programming languages is not always in best interests of the user unlike an up-to-date web browser. Then when they find out x doesn't work or exist in 3, they badger whoever wrote a library for 2 to port. Those people really need to port it themselves and maintain it afterwards. They don't, and it's just an ugly situation.

For example, you can build iOS/Android apps using Kivy. Guess what, can't build for iOS unless you use 2.7! Just lots of surprises out there for those who start off wanting the "latest version". It's not the latest version, it's a new, breaking language. If you end up doing much cobbling with Python, this may be of interest to you.

I have my doubts 3 will get over the hump, and just plan on waiting till the complainers turn into maintainers and 99% of everything is ported. Then I'll use Python3 if I don't find something else I like more before then.

there is nothing wrong with py3. some people just want to be ornery.

Take a look at julia!

It looks like you're looking at an earlier version of Swift at least based on the fact that you're talking about Xcode 6.1 at the start. If you're covering 1.2, you probably should update that.

Thanks. The code is 1.2, but the Xcode references are out of date. I'll update soon, I'm also going to update the whole thing to Swift 2 when it's released.

Would you mind removing or moving all of the position:fixed stuff on the left? Makes it impossible to read the site on mobile.

Was it the share buttons? I tested these on iphone and they dropped to the bottom of the page. But it looks like they only do this for phones below a certain resolution. So I've removed them.

Yep yep. Just put em somewhere where they're static, or use a media query to position:static on < 768px. Excited to read the book now. =)

"For anyone who has been programming in a modern language such as Ruby [1995], Python [1991], Clojure [2007], Haskell [1990], etc, and who was put off developing iOS apps by Objective-C, Swift marks a new era."

You say modern but I don't think it's really what you mean here.

Your descriptions of Ruby vs Obj-C make it seem that really what you mean is high-level; that is, to a newer programmer, easier.

These languages (Haskell excepted) make it very easy to do simple things. Describing them as "modern" in contrast with the implicitly antiquated Obj-C makes it a little hard to take your assertions seriously.

Verbosity is a claim to make, age is not.

Thanks for sharing it :) just fyi, the .fixed header overlaps the content making links unclickable if they are in the top part of the page

Thanks for letting me know, I hadn't noticed that.

The ebook is great, but it's missing complete start to finish examples. Pad it out with them and you could double the price (and it would be massively more helpful!). Maybe a todo app, flappy bird clone, etc.

Thanks for the suggestion. I think I'll add another chapter at the end that walks through a longer example start-to-finish.

Not sure if you have a better method for getting feedback. First sentence in 12.6 has a minor typo: "“Subscripts allow you *do define a way of allowing your class”

I believe you just need to remove 'margin-bottom: 2em;' from .top-bar in styles.css

Thanks, I'll try that. Although I'm reluctant to clear the cache until it goes off the HN front page :)

With what did you create the ebook?

I used Softcover (https://www.softcover.io/) to generate the ebooks.

Softcover is awesome. (It's a Michael Hartl creation.)

Online version of reading has complete book?

I'd highly recommend Functional Programming in Swift for more intermediate topics. By Eidhof, Kugler, and Swierstra


No affiliation to the author/book.

Shameless plug - I made a site that gathers resources for learning Swift. Will be adding this shortly :)


Cool. Bookmarked.

Ooh. Thanks.

I like the style, brevity, and practicality of the book (at least the first few chapters; haven't read it all yet). Good stuff and good luck with it.

I did find the first few examples with the REPL to be a bit confusing. Were you using a function before it was defined?

Thanks :) The REPL example with the error has a deliberate typo (int instead of Int) to show how multi-line editing works in the REPL - is that the part you're asking about?

I was referring to this:

$ swift Welcome to Swift! Type :help for assistance. 1> 3.14 * 2.5 * 2.5 $R0: Double = 19.625 2> println("The area of the circle is \($R0)") The area of the circle is 19.625 3> 4> $R0 * 2 $R1: Double = 39.25 5> println("And double that is \($R1)") And double that is 39.25 6>

What's Double? Trying to follow this (which didn't make sense to me because I didn't know the history stuff was there) simply caused error messages.

Isn't Double just a bigger floating point number?

Right. A double has twice the precision of a float (hence the name). It's also the default floating point data type in Swift.

Slight tangent, but are there any recommended guides/books/videos for leaning the iOS frameworks with swift?

I have recently started programming on iOS with swift. I got my head around the language just not any of the frameworks, specifically UIKit.

I love the Lynda.com videos on Swift and iOS. The latest Stanford iOS course uses Swift and is excellent.

I'll second the Stanford iOS course with Swift, here's a link to it on iTunesU: https://itunes.apple.com/us/course/developing-ios-8-apps-swi...

Also, Udacity has some iOS courses using Swift now as well. Here is the intro one: https://www.udacity.com/course/intro-to-ios-app-development-...

This is very helpful. Thanks for sharing! Great that it's free too :)

This is fantastic, just what I was looking for, a very quick intro to swift that assumes I'm already a programmer.

The Apple docs, at least last time I tried reading through them, were like wading through treacle so this is a great alternative! I just read the first couple of chapters in 10 minutes and got all the key info I wanted with no fluff - great job!

One edit suggestion - I've noticed a couple of times so far that "it's" is used incorrectly, for example in this sentence:

> You can’t change the type of a variable once you’ve declared it. It’s type is fixed at the time it is declared.

I assume you know the error here but on the off chance you don't:

it's = it is (it's a Bool) / its = the possessive of it (Bool is its type)

It's a little jarring so you might want to go through and fix these.

Cheers for the book! :-)

Thanks for that - I'll fix the errors you've listed. I know how to use its and it's, and I've proof-read the book several times, but there's still a good bit of stuff like this that I've missed.

It turns out that it's really difficult to proof-read large blocks of text that you've written yourself :/ When your brain sees something it recognises it tends to speed up and skip over bits, seeing what it wants to see, thus missing stuff like this.

No probs, and great choice of model by the way, offering the web version for free.

For learning a programming language I actually prefer the web format to the ebook. Now I've figured out how useful this book will be by reading a few chapters, I'll certainly purchase a copy anyway, $12 is more than reasonable for the value this provides!

In Chapter 4, you have a typo: "dynamicly" should be "dynamically"

Thanks, fixed.

I love this. Btw, totally off topic : Is it possible to write iOS/OSX apps by learning Swift without the knowledge of ObjC ? My background : I know some Java/Ruby and do some Android apps.

It is, but you'll still need to learn about the memory management in objective-C (retain / release and such, although that's been made a lot easier over the years, pushing it back to being background knowledge) and - perhaps more importantly than the actual language - the frameworks, environment and tooling (Foundation, UIKit, iOS application basics / lifecycle, view hierarchy, XCode, Interface Builder, and background knowledge like accessibility and such).

But yeah, go with Swift, it's closer to Java than Objective-C is.

Nice, I'm learning Swift from your site. The kerning for Chapter "10.4" is killing me though. Other than that I'm enjoying going through it. :D

Have just started learning Swift. Have favourited, and will be sure to give some feedback once I've made my way through the whole thing. Good luck with it!

Hi Aidan, your about Author section has a typo says'bulding' rather than building.

Thanks, fixed.

Looks awesome! Thanks for your time I will definitely look into it deeply soon!


Just because it will go out of date at some point, it doesn't mean it's not a useful resource today.

I haven't read this particular book, so can't comment on whether or not it's any good, but in general whenever I want to learn a new language, I start by looking for a book.

Well, at least it will be useful short term.

Your comment doesn't even have that.

Nearly every technology book will be out of date shortly after it is written. You want people to just stop writing and sharing?

What have you done that's so great that you can observe and criticize the lessers from your great pedestal?

Sorry, but this guide is not as comprehensive or updated as the official documentation [1]. Just compare the generics or memory management sections to see why you would want to read the official documentation. Maybe a high level tour of swift but you certainly are not going to learn swift with this guide.

[1] https://developer.apple.com/library/ios/documentation/Swift/...

You're right - it's not as comprehensive as the official documentation, nor is it meant to be. It's a quick tour of the main language features, with a particular emphasis on the parts that I (as a ruby, python, clojure dev) found interesting.

For comparison, the Apple book "The Swift Programming Language" comes in at 334 pages. "Learn Swift" comes in at 128 pages.

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