I ve been reading on composition over inheritance in Kotlin

Question

I ve been reading on composition over inheritance in Kotlin and came across a few articles like this <https medium com the kotlin chronicle why you should use class delegation in kotlin fb0a3ebf151e> One way Kotlin helps to reduce boiler plate code is by using class delegation and the `by` keyword This looks great and I like it so far However during the closing panel of KotlinConf 2018 Andrey and another guy said it was their least favourite feature Does anyone have any opinion or bad experience with class delegation

Pascal How · Answer

< ghedeon> < sindrenm> Are you both saying you had bad experiences with class delegation sweat smile

sindrenm · Answer

Nah I love it

sindrenm · Answer

Or I love that it exists But always use the right tool for the job Inheritance has its place composition has its place and inheritance by delegation has its place I would just consider the use case and choose whichever tool you feel works best Which is the worlds most boring answer but there it is stuck out tongue

ghedeon · Answer

My reaction was more like Also interested in this subject You put it nicely after those words at kotlinkonf it s not clear what s the deal with class delegation

sindrenm · Answer

Honestly Andrey s I really hate inheritance by delegation doesn t really give me much to go by Would love to hear a more thorough explanation simple smile

Pavlo Liapota · Answer

I believe that they don t like how this feature is implemented supported in a language and not that the feature in itself is bad The syntax is a bit limited right now and it would be great to have more general solution For example I have found this KEEP <https github com Dico200 KEEP blob ibd enhancements proposals implementation by delegation enhancements md>

Pascal How · Answer

Thanks guys Also < Pavlo Liapota> you may actually be right there Perhaps it s to do with the way class delegation is implemented as you say It would be nice to see examples where the behaviour is unexpected or where the current implementation has limitations

karelpeeters · Answer

It s frustratingly limited right now eg you can t get access to the delegate instance at all

sindrenm · Answer

That would make sense It does indeed have its limits but the idea is good Thanks

Pascal How · Answer

That s a very good point actually