Shiveen Pandita

Equality Checks in Kotlin With Unstructured Data

This is a small blog post on equality checks in Kotlin when one of the objects may contain arbitrary data.

Let's say you have an object that looks like:

data class ArbitraryData(val id: UUID, val someData: Map<String, Any>)

where someData is any json map of data that could contain any untyped data at runtime.

Now, if you have two instances of this object with the same data and try to compare the two using the regular equals method, you would get a false result.

arbData1 == arbData2 results in false.

This is due to the default Map equality implementation for Kotlin, basing the check on same references for the objects. Hence, even if you have the someData maps in both objects populated with the same value they will fail.

To get around this little dilemma, you need to override the default equals implementation for ArbData class and manually compare the values.

data class ArbitraryData(val id: UUID, val someData: Map<String, Any>) {
    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (other !is ArbitraryData) return false
        if (id != other.id) return false
        return someData.entries.all { it.value.toString() == other.someData[it.key] }
    }
}