Channels
#announcements
- a
apatrida
05/23/2017, 2:05 AMso they should only call that version of the constructor if they have values. otherwise call the one that omits channelIds - a
apatrida
05/23/2017, 2:05 AMor you could create factory methods that do this logic, instead of constructors - a
apatrida
05/23/2017, 2:05 AMor you could not use a data class and then have more logic there - a
armaxis
05/23/2017, 2:06 AMCopy code//in foo.java @Nullable private List<String> getIds() {...} ViewportInfo info = new ViewportInfo(100, 200, getIds()); - a
armaxis
05/23/2017, 2:06 AMthis won't work, right? - a
apatrida
05/23/2017, 2:06 AMnon data class:Copy codeclass ViewportInfo(channels: List<String>? = null, val startTime: Long, val duration: Long) { val channelIds: List<String> = channels ?: emptyList() } - a
apatrida
05/23/2017, 2:06 AM(but I would still put optional last instead of first) - a
apatrida
05/23/2017, 2:07 AMdo you really need a dataclass? - a
armaxis
05/23/2017, 2:08 AMyes, I need equals/hashCode/toString - a
armaxis
05/23/2017, 2:08 AMrare case when I actually use those 🙂 - a
apatrida
05/23/2017, 2:09 AMyou can generate them too using Intellij to use the normal class. - a
apatrida
05/23/2017, 2:09 AMor make a factory and hide the constructor:Copy codedata class ViewportInfo private constructor (val channelIds: List<String>, val startTime: Long, val duration: Long) { companion object { @JvmStatic fun create(channelIds: List<String>?, startTime: Long, duration: Long): ViewportInfo { return ViewportInfo(channelIds ?: emptyList(), startTime, duration) } } } // from java: ViewportInfo something = ViewportInfo.create(null, 10, 1); - a
apatrida
05/23/2017, 2:10 AMyou are doing something odd for Kotlin to be nice to Java, so your Kotlin code will not be as pretty, and you have to live with that to handle the evil null as a value - a
apatrida
05/23/2017, 2:10 AMor last option: - a
apatrida
05/23/2017, 2:11 AMuse a constructor but hide the channel id val, and make it another derived property.Copy codedata class ViewportInfo (private val rawChannelIds: List<String>?, val startTime: Long, val duration: Long) { val channelIds: List<String> = rawChannelIds ?: emptyList() } - a
apatrida
05/23/2017, 2:11 AMand by the way you should NEVER make anything mutable that is hashcode and .equals if you put these things in sets or maps. So having a
seems really bad.var - a
apatrida
05/23/2017, 2:11 AMwith the last example you can pass in the null, and then you still have your normal property - a
armaxis
05/23/2017, 2:12 AMYou're right, I'm doing something that is not very kotlin-ish, pretty much saying "Hey, I want you to have a non-null field, but you will still accept null field and replace it with something else, just because other files are not kotlin yet" - a
apatrida
05/23/2017, 2:12 AMwell, you have all possible options above, pick one 😄 - a
apatrida
05/23/2017, 2:13 AMnote in the last example that the derived property is not used for the hashcode/equals. And likely null vs. emptyList will not be equal - a
apatrida
05/23/2017, 2:13 AMbut might be good enough - a
apatrida
05/23/2017, 2:13 AMenjoy! - a
armaxis
05/23/2017, 2:14 AMthank you! - a
armaxis
05/23/2017, 2:14 AMI think I'll go with the most logical one:data class ViewportInfo (val channelIds: List<String>, val startTime: Long, val duration: Long) - a
armaxis
05/23/2017, 2:15 AMand correct other places so there is no passing ofnull - a
apatrida
05/23/2017, 2:15 AMeven in Java, I never pass nulls for lists - a
apatrida
05/23/2017, 2:15 AMso good practice - a
apatrida
05/23/2017, 2:16 AMyou can still provide a default for Kotlin callers if you want, but if it is the first parameter it won't be so nice to omit - a
armaxis
05/23/2017, 2:16 AMand that note about having list as
- that actually brought up a problem on java side, I'm looking into right nowvar - a
apatrida
05/23/2017, 2:16 AMthe
needs a reason to bevar
otherwise pickvar
alwaysval👍 1