5 Fun Ways to Use Extension Functions in Kotlin

[@TimSchraepen]

Nice overview. I can see some of them being useful in custom DSL’s.

[@typealias]

Thanks Tim! Yes, I agree - a custom DSL would be a great context for some of them!

[@martingaens2073]

Haha yeah I can confirm this is indeed a great way to teach about these funky operators. Kotlin has quite some flexibility with these things. Great vid :)

[@typealias]

Thanks, Martin - Yes, those operator conventions allow for some pretty neat possibilities!

[@victoryghor9009]

I am studying kotlin, and really love your material it's soo easy to understand with this simples examples, please continue your channel.

[@typealias]

That's great! Thanks so much for your kind words, Victor! I'll keep up the videos!

[@Alchemist10241]

10:54 - this operator extension function is very useful, by using this extension function I saved a lot of time when I was working on a project that had a lot of Maps in it

[@typealias]

That's great! I never had a need to use that one in a real app, but I'm glad to know it worked well for your project!

[@stephanbranczyk8306]

Wow! This is a gem of channel. I'm glad it was recommended to me

[@typealias]

Thanks, Stephan! I'm still figuring out what kind of videos are most helpful for everyone, so I'm glad to hear that you're happy with the channel so far!

[@LifeLessonsLearned8587]

Absolutely amazing!! This channel is gem!!

[@typealias]

Thanks so much, Vivek! 🙂

[@theblueplanet3576]

Thanks for sharing this. The last one with combination of infix and extension function was crazy but useful 😁

[@typealias]

Thanks! Haha, yeah, that one is a little crazy, and it might leave some fellow developers scratching their heads. But it sure is fun to explore all the crazy possibilities! 😁

[@blaupunkt1221]

That was really interesting and easy to understand. Thank you for showing this!

[@brianlcooley]

Just discovered your channel today. Great stuff, Dave!

[@typealias]

Hey, thanks so much, Brian! Glad you're here!

[@jackli1924]

Awesome Video! Thank you Dave You always explain things deeply and concisely and easy to understand. beside, I have a question any function in Kotlin can be defined as a operator function or only the operator methods in Kotlin standard libraries can do these things. Thanks a lot for your amazing and excellent explaination!

[@typealias]

Hi Jack, thanks so much - I'm glad the video was helpful! You can add the "operator" modifier only to functions with particular names. You can find the full list on the "Operator Overloading" page in the Kotlin documentation here: kotlinlang.org/docs/operator-overloading.html. On that page, each section has a table with a column heading that says, "Translated to". You can use the "operator" modifier with a function that has any name under that heading. Let me know if you have any other questions!

[@jackli1924]

@@typealias Thanks a lot for your quick reply！ waiting for your new videos about kotlin tech. Your videos are so amazing and exlpained so concisely and deeply! that really informative.Keep doing it, waiting for more!

[@systweaker]

Inspiring techniques, ta!

[@jaredandrews9988]

Really great video man, hope to see more!

[@typealias]

Thanks Jared! I'm hoping to do at least a few more!

[@smreha]

I was blessed by the YT recommendation algorithm as 1 of your videos showed up. It was an instant sub which is very rare for me. Keep up the good work 👍

[@typealias]

Hey, I'm thrilled to hear you're enjoying the channel! Glad to have you here! 🎉

[@rajushingadiya2860]

Totally mind blowing sir , we want more and more and more like this tricks make it more hard then more hard then take to KSP level code . dev like me are more getting hungry after learning your those magical spell again i love it when sound "ha ha ha" after archiving magic ✨ you took totally good decision about to make video instead of blog (blog are also good) but video just bring you alive in front of us also sounds clear and cut to me when you just draw on video about contains and in are opposite. your big fan - Raju Shingadiya

[@typealias]

Thanks so much, Raju! I'm glad you enjoyed this video so much! And thanks for the feedback about it. I'll plan to make some more videos, since it seems to be an effective way to share this kind of information. 🙂

[@rikaryu5411]

Thank you very much! Such great videos. They really stand out from the rest of the similar content because of the way you explain everything - very clear and concise way of putting everything, helpful and comprehensive examples, nice pace and non-trivial topics and also fun! I guess you might even pick the topics that are more trivial and still your videos will be just as good. Please keep doing it :)

[@rikaryu5411]

Also that would be awesome to watch something about Coroutines on your channel!

[@typealias]

Thanks so much for the feedback, Rika - I'm glad to hear that these videos have been helpful and entertaining for you! I'll add coroutines to the list of ideas for upcoming videos. 🙂

[@jameslorenzen2610]

Excellent video Dave! One thing that would have been nice to demonstrate is how one can easily locate the extension functions. For example, in your last example, can one in Idea CMD+Left Click to jump to the extension functions? I would assume so. One thing that has frustrated me about the plethora of extension functions on a large project is being able to know when an extension function is being used and when it isn't. Along with being able to easily jump to the code to see what it is doing. Anyways, great job. Very high quality!

[@typealias]

Thanks for the great feedback, James! Yes, you absolutely can command-click through to the definition of an extension function, so if you're ever in doubt about what code it'll run, that's a great way to make sure. As for knowing when you're calling an extension function, you could check your IDE color scheme (at Preferences > Editor > Color Scheme > Kotlin > Functions > Extension function call). By default, I think extension function calls are italicized but otherwise look similar to member function calls. You could change it to a color that stands out more. Just keep in mind that there are lots of extension functions in the standard library (scope functions, collection operators, etc.), so changing this setting will light those up as well!

[@andyli619]

very very amazing and excellent video!

[@typealias]

Thank you, Andy! 🙂 Glad you liked it!

[@_MrKekovich]

Your voice and explaining flow is amazing. I really like this channel.

[@typealias]

Hey, thanks so much! I'm really glad to hear that you're enjoying it!

[@user-by7zo1rp6l]

Dave, thank you for your work and all your videos. They are very professional and positive. I found them easy to watch and consume information... at the same, they provide a lot of "concentrated" information about their topic. Thanks again, and, please, keep doing more videos! P/S I've recommended your channel to my colleagues.

[@typealias]

Thanks so much, Grigory! Glad to hear that the format seems to be working well. I'll keep at it! 🙂

[@puntouan]

Thank you very much for your generosity in creating this type of content! Congratulations! I think it's a great job!!

[@typealias]

Thank you so much! I'm glad to hear that it's helpful!

[@HoussamElbadissi]

I'm a bit late here, but hopefully the limitation around extending classes with Companion objects will hopefully be lifted with the introduction of actual static functions into Kotlin. The Kotlin team seems to be pretty serious about that feature, and they'll largely replace most uses for Companion objects. That way we can do this: static fun BigDecimal.from(value: String): BigDecimal = ... I think they'll also mostly behave (on the JVM at least) like Java static functions, which might be better for performance and code size.

[@typealias]

Ah yeah, I almost forgot about that one! They had mentioned it at KotlinConf 23, but I haven't heard much about that lately. Now that K2 is out, I expect we'll start seeing a lot more action on some of these features. ( For anyone who comes across these comments and wants more background, you can read the KEEP for that topic here: github.com/Kotlin/KEEP/blob/statics/proposals/statics.md )

[@HoussamElbadissi]

@@typealias Yeah, exciting times ahead 😁 By the way KZbin seems to have included the parenthesis in the URL, you might wanna add a space there 😅

[@typealias]

Haha, thanks! That's not the first time I've fallen for that - putting a link inside parentheses! 😅

[@sanketnaik2082]

Hey Dave, keep them coming! I have enjoyed all of your videos thoroughly. Pure gold😍

[@typealias]

Thanks so much, Sanket! 🙂 I'll keep at it!

[@ayodelekehinde]

Wow. I loved it. More please 🥺

[@typealias]

Thanks Ayodele! 🙂 I'll keep at it!

[@trido8135]

This video is rlly awesome, you got a subscriber😂

[@typealias]

Thanks so much! I'm glad you liked it! 🙂

[@diegofarias6337]

Muito bom o conteúdo, sua explicação e didática são ótimos. Thank you , very good.

[@typealias]

Thank you so much, Diego! I'm glad you enjoyed it!

[@CommanderSteps]

This was really entertaining. 🙂

[@typealias]

Haha, thanks Stefan! That's what I was aiming for with this one! 🙂

[@BenjaminShults]

You actually don't need the Vehicle class anymore. You can put the default implementation in the interface itself.

[@georgeshalvashvili6270]

Nice

[@typealias]

Thanks! 🙂

[@user-jz9dm9xr2n]

It's very cool. Good stuff and good teacher.

[@typealias]

Thank you so much! 🙂

[@L4szcZ]

avesome tricks!

[@mefodymo7456]

Cool!

[@prestonc.4875]

Nice! Thank you.

[@typealias]

Thanks Preston! 😁

[@vengateshm2122]

Wow!

[@gayrimesruturk783]

still works as of whatever day it is

[@typealias]

Haha, yes - around the 1:15 mark, I accidentally kept the variable name "today" after changing the value to the Kotlin 1.0 release date. This video was actually recorded only a week or so ago. 😅

[@lengors7327]

Thanks. I'm now gonna use these tricks to write unreadable code so then only I know what it does and cannot, therefore, be fired! So, again, thank you so much!!! (No, but for real, great info in the video 😀)

[@typealias]

Lol, yeah! At least since Kotlin is statically typed, this kind of "magic" is easier to figure out (e.g., compared to my experience with Ruby), since you can just cmd+click to definitions. But still, it can definitely be a great way to confuse your coworkers! 😅

[@nipunshah1373]

How come invoke() works for `()` & `{}` Does callable means () & {} both ??

[@typealias]

Hi, Nipun! Actually, invoke() only works for `()`. The trick I used here was due to trailing lambda syntax - as you probably know, if the last parameter of a function (even if it's the _only_ parameter of the function) has a function type, you can omit the parentheses and just use the braces of the lambda... kind of like we'd usually do with scope functions like let, also, apply, etc. So in other words, we could have written it as double({ 12 }) instead, but I was specifically aiming to make the syntax work with just braces. That custom invoke() function just calls the lambda, and relays its result to the receiver object. Of course, this was just for amusement - I wouldn't recommend pulling these shenanigans with a real project, or else your colleagues will not be very happy! 😁

[@rafaelacioly3252]

🤩

[@rcalencar79]

Today is 2016-02-15? ;-) Great video!

[@typealias]

Haha, I intended to update that to just say "date" - I opted to use the Kotlin 1.0 release date instead of the current date... but clearly forgot to change the variable name! 😅

[@IncompleteTheory]

And .... the obfuscated Kotlin contest is born! 🎉😂

[@typealias]

Haha, yes! I'd love to see what others come up with! 😅

[@ErikBongers]

Hmmm ... that's even weirder than JavaScript.

[@typealias]

Yeah, things can get surprisingly weird in Kotlin if you try hard!

[@olehmasterluck]

Wow! You are a kotlin cheater! :-)

[@typealias]

Haha, yes - it does feel a bit like cheating! 🙂

[@randominternet9338]

you make it so complicated for no reason what so ever

[@CrapE_DM]

Wow, I didn't think the `date in Month.FEBRUARY of 2016` would work without putting parentheses around the last 2. Just gotta be wary of someone creating an `infix fun Boolean.of(num: Int)` function that could make it possible to go left-to-right.

[@typealias]

I poked around with this a little - looks like the infix functions are indeed processed left-to-right. I suppose the reason it's not a problem here is that `in` itself is not an infix function. Interesting stuff!

[@rajushingadiya2860]

Totally mind blowing sir , we want more and more and more like this tricks make it more hard then more hard then take to KSP level code . dev like me are more getting hungry after learning your those magical spell again i love it when sound "ha ha ha" after archiving magic ✨ you took totally good decision about to make video instead of blog (blog are also good) but video just bring you alive in front of us also sounds clear and cut to me when you just draw on video about contains and in are opposite. your big fan - Raju Shingadiya