how to access a value in a map that is nested inside another map (in kotlin)

Question

In the example below, a map called someCompany have a map called somePerson in one of its values

val somePerson = mapOf("name" to "Tim", "age" to "35")

val someCompany = mapOf("boss" to somePerson, "sector" to "accounting")

I thought it would be simple to get a value inside the nested map. I'm kind of surprised this naive solution doesn't work:


val a = someCompany["boss"]

val myOutput = a["name"] //I expected myOutput to be 'Tim', but this doesn't work

How can I extract a value inside a nested map?

Can you try val myOutput = a.get("name") ? To access values of the Map object, you need to use the get() method — Kartik
– Kartik, Commented Dec 10, 2022 at 6:42
@KartikShandilya I've tried, but this doesn't work. The output is an error: Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: public operator fun MatchGroupCollection.get(name: String): MatchGroup? defined in kotlin.text — Henrique Rigitano
– Henrique Rigitano, Commented Dec 10, 2022 at 6:55
The problem is that your map has inconsistent value types. One of them is a Map, but the other is a String. So when you retrieve a value, it has the common supertype, Any. — Tenfour04
– Tenfour04, Commented Dec 10, 2022 at 6:59

Javlon · Accepted Answer · 2022-12-10 07:03:22Z

3

You have to declare your maps like this:

val somePerson = mapOf("name" to "Tim", "age" to "35")
val otherPerson = mapOf("name" to "Tom", "age" to "25")

val someCompany = mapOf("boss" to somePerson, "sector" to otherPerson)

your sameCompany map needs to have the same type of data to work properly

and you can access name of the person by using get() method:

val person = someCompany["boss"]
val name = person?.get("name")

P.S.: if you really want to create your map with different types of data, you can cast retrieved value to your preferred type(but I wouldn't recommend it, as it is unsafe):

val person = someCompany["boss"] as? Map<String, String>
val name = person?.get("name")

edited Dec 10, 2022 at 7:03

answered Dec 10, 2022 at 6:56

Javlon

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