How to get property of object dynamically in kotlin

Question

Say for example I have the following object...

val ob = Thread.currentThread().getStackTrace()[2]

...and I want to select a property from this via a dynamic variable. ob.<property> would work normally but what if I didn't know <property> at compile time?

Is it possible to run something like ob[<property:str>] (as is the case in javascript, python etc) in kotlin?

This is called reflection. There are many questions about this subject already on here. kotlinlang.org/docs/reference/reflection.html — Tenfour04
– Tenfour04, Commented Aug 8, 2020 at 15:37
Also: it's best to avoid using reflection unless there's no other way. It's slow, fragile (as many errors which would otherwise be spotted at compile-time must be handled at run-time), hard to read, and hard to refactor. It's great for compile-time tools, frameworks, plug-ins, &c; but for general-purpose coding there's usually a better approach. — gidds
– gidds, Commented Aug 8, 2020 at 15:44
you can have the expected objects implement a common interface — sidgate
– sidgate, Commented Aug 8, 2020 at 19:40

Lutosław · Accepted Answer · 2022-02-01 22:02:36Z

1

Yes it is, there is a nice library kpropmap. We use it on production because we just need to have a Map<String, *>, but I wouldn't recommend using it for accessing fields.

https://github.com/rocketraman/kpropmap https://mvnrepository.com/artifact/com.github.rocketraman/kpropmap

After adding a dependency you can just write

val map = propMapOf(obj)
val name = map["name"]

However it'd much better if you were able to cast the obj to some known type and access the property statically

(obj as? SomeInterface)?.name

answered Feb 1, 2022 at 22:02

Lutosław

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