kotlinlang #server

@Viacheslav Petriaiev IMO in a sealed class hierarchy without inheritance or place shared behaviors in interfaces and properties in their corresponded data classes. If you have a concrete minimal example we can see what the issues are.

Viacheslav Petriaiev

02/01/2018, 4:23 PM

@raulraja I need tranlate code similar to this one in java

raulraja

02/01/2018, 4:26 PM

@Viacheslav Petriaiev can you add that as a code snippet instead of a message? It would look something like this:

Copy code

sealed class Payment {
  // shared behaviors of all payments
}
data class InternationalPayment(val countryCode: String) : Payment()
data class OtherPaymentType(val other: String) : Payment()

Viacheslav Petriaiev

02/01/2018, 4:28 PM

@Viacheslav Petriaiev uploaded a file: Untitled

Untitled.java

Viacheslav Petriaiev

02/01/2018, 4:29 PM

@Viacheslav Petriaiev uploaded a file: Untitled

-.java

Viacheslav Petriaiev

02/01/2018, 4:30 PM

I've added as a snippet

raulraja

02/01/2018, 4:30 PM

You can also add properties to the

Payment

constructor and override them as needed on each of the data types extending Payment

raulraja

02/01/2018, 4:31 PM

I presume the limitations of data classes extending other data classes is related to

equals

hashcode

and others being auto generated and synthetic and only being able to account for the properties declared on the data type.

raulraja

02/01/2018, 4:32 PM

If you don't wish to model this as an ADT with sealed classes which in my opinion is a superior solution for this you could just translate those Java classes to regular Kotlin classes and then you can implement equals, hashcode, etc in the same way.

Viacheslav Petriaiev

02/01/2018, 4:34 PM

What do you mean about "add properties to the constructor and overriden them"? Could you give me some code sample or link?

Viacheslav Petriaiev

02/01/2018, 4:35 PM

like this one? https://stackoverflow.com/questions/26444145/extend-data-class-in-kotlin

raulraja

02/01/2018, 4:35 PM

Copy code

sealed class Payment(val amount: BigDecimal) {
  // shared behaviors of all payments
}
data class InternationalPayment(val countryCode: String, override val amount: BigDecimal) : Payment(amount)
data class OtherPaymentType(val other: String, override val amount: BigDecimal) : Payment(amount)

raulraja

02/01/2018, 4:37 PM

This encoding will ensure

equals

hascode

etc are properly implemented derived from the structural shape of each individual data class.

araqnid

02/01/2018, 5:15 PM

I think you want an

abstract val amount: BigDecimal

property in the Payment class, rather than a constructor parameter

araqnid

02/01/2018, 5:16 PM

otherwise technically you're storing the value twice

araqnid

02/01/2018, 5:16 PM

might not matter

Viacheslav Petriaiev

02/01/2018, 5:31 PM

any suggestions if I need 3+ level inheritance? level 1 - library level has some system parent AbstractDTO with some system properties(String someSystemUUID) level 2 - AbstractPayment level 3 - InternationalPayment AbstractDTO cann't be the sealed class, because it' common class Can I give inheritance like this one? abstract class AbstractDTO data class InternaltionalPayment : AbstractPayment sealed class AbstractPayment : AbstractDTO with equals()/hashCode() which drill down all this hierarchy?

araqnid

02/01/2018, 5:54 PM

that could work, try it

araqnid

02/01/2018, 5:54 PM

as long as the base classes only contain abstract properties, then the data classes will be responsible for generating equals/hashCode for all the actual properties, and that's ok

fred.deschenes

02/01/2018, 6:01 PM

I'd probably have both "abstract" things as interfaces, with default functions in them for whatever is necessary

➕ 1

fred.deschenes

02/01/2018, 6:03 PM

something like that : https://gist.github.com/FredDeschenes/2ef35f259b0e2065255e6fd2df87cf88

Viacheslav Petriaiev

02/01/2018, 7:35 PM

@raulraja @araqnid @fred.deschenes I was tried to solve problem with mind of java-developer. Thanks a lot for help

👍 2

anderson.faro

02/03/2018, 10:42 PM

hey guys, a question

anderson.faro

02/03/2018, 10:43 PM

your opinion, whats is the best framework web for kotlin?

orangy

02/03/2018, 10:48 PM

It hasn’t been invented yet. There are approximations that are more suitable to specific scenarios.

🤣 1

☝️ 1

anderson.faro

02/03/2018, 11:05 PM

i got it

anderson.faro

02/03/2018, 11:14 PM

the Spark is good choice?

asad.awadia

02/03/2018, 11:27 PM

how much power do you need?