while interviewing a 10 year experienced .net developer I asked, do you know Liskov substition principle.

And he was like 'what cow???'

Me: Faceslam!!!

Harsh question, surprised he didn't walk out

2 questions...

1) Where would you expect them to have learned of or encountered this? I've 15+ years in OO programming and have never heard of it either.

2) Where in your organisation's code base, or in any of your projects histories has knowledge of this principle been essential?

I never understood Liskov's either...

@g-m-f yeah, this stuff sounds more orientated towards a designer.
Glad I've never been asked that question

@Lasse Basically Liskov says that you always should be able to use a derived class everywhere you use the base class without that altering the functionalty. That means that the derived class should not alter the base class functionality, just extend it with new funtionality. You see? :)

To really find out if the candidate gets it, ask them to show a violation of LSP. That shows if they have just learned the definition, or really understood it.

@uxmedic: makes sence! Thx

10 year vet checking in... I had heard of it but forgot. Not sure if I've written code that violates it or not.

I've spent my career working at small businesses under senior devs without senior knowledge and working with code bases that have only taught me worst practices.
I can read a book or tutorials online about advanced principles like this but it's not easy to apply them in the small business real world that I live in. My boss wants me to get shit done fast and often times doesn't care about the long term maintainability of the app.

It's not right but that's how I got here. I'm not against it though.

@shittywebdev: I feel your struggle!

For whoever wants the clean code book he is talking about for their pdf collection: www.ricardogeeks.com/docs

solid principles are not really essential to build a decent app, it does help in billing your client and increase your time line for the project

@0xH4lcyon link is dead, however it may just be me, please confirm?

Apologies, there isn't supposed to be an 's' before com

Working link for full book free: http://www.ricardogeek.com/docs/

@0xH4lcyon @h3ll thanks guys!