Variance... without Generics!

Did you know that you can use covariance and contravariance in Kotlin without generics? Unlock the mental model of generic variance by first understanding how variance works with regular type hierarchies!

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00:00 Introduction
00:35 Upholding the Contract in Subtypes
02:05 Covariance
04:12 Contravariance
06:54 Summary of Variance
07:15 Why Generic Variance Works
08:10 Wrap-up

#kotlin #androiddevelopment

[typealias]

Big thanks to the folks who joined the premiere and said hello in chat! Maybe we can do that again next time. I'm also considering whether an occasional livestream would be helpful, where I might be able to respond to chat questions and comments in video instead of text. Anyway, if you've got thoughts about any of that, let me know!

[Mike-erih]

I do not know how you do it Dave but you explain everything so clear. I guess its what they call a teaching talent!

[JentaroYusong]

I loved this episode! Always had trouble with the nomenclature. Using a non-generic example is really helpful, thank you!

[randoman]

Best explanation on this topic I've seen. Great work!

Thanks youtube for recommend this channel. It definitely deserve more views! You teach as clear as day, even though I'm not a native english speaker. Thanks for sharing your knowledge.

[dilin]

It takes a very deep understanding of a subject and a creative mind to bring such simplicity to a somewhat complex concept, in a lucid manner.
Thank you.

[mohammad-rezaei]

That is why they say teaching is an art, and how beautifully you share this art

[holonaut]

Awesome! I'm learning Scala rather than Kotlin right now, but this idea of "return types can become more specific, parameter types can become more general" is a principle that applies logically to uphold contracts.

[robkeazor]

Bro, the way you explained thus was flawless. Thanks

[gekylafas]

One of the best explanations of variance I have seen/read! Thanks!

[olivierm]

Your online book and videos are great and useful. Cannot recommend enough. Thank you sir!

[husammuala]

Thank you so much! Clean explanation and straight to the point. Please continue uploading videos <3

[nasimnajand]

This is so awesome that you explain in the most simple way. Thank you in advance 🙏

[СергейУсачев-мг]

This is the best explanation I ever heard! Please dont stop doing your lessons. Also want to say thank you for your book, this is really perfect!

[asadullahilyas]

This is one of the brilliant videos on YouTube. Mind blowing explanation. Thank you Dave. You are doing an excellent job. Keep it up.

[AntonioLeivaCom]

I love your videos! I’m always struggling to understand and retain in my brain these to concepts, and this one will help a lot!

[sevbanthebuyer]

Great ! Very comprehensive, thank you for your effort.

[Alchemist]

I never completely know in and out keywords, Now I totally get it, well don

[LszcZ]

amazing work, you don't even know how much I apprecaite your content!

[avalagum]

OMG! Today I understand a bit about covariance and contravariance. Thank you so much.