De-serializing Duration Member In Data Class Kotlin

I have a data class like below that has a member of type Duration:

@Serializable
data class DataClass(
    val fieldOne: Long,
    val fieldTwo: String,
    val fieldThree: Duration,
) {
    constructor() : this(0, "", Duration.ZERO, "")
}

I am working with Firebase Realtime Database to store this DataClass and am encountering an issue when I de-serialize a DataClass object.

I am seeing that even though the value held in fieldThree gets stored appropriately in Firebase Realtime Database, when de-serializing it in the application, the value is zero (0).

This happens because of the default constructor in place and I don’t understand why.

I need the default constructor or else I will get an error while de-serializing stating that a default constructor is missing from the DataClass.

I am aware that I need Kotlin 1.7.20 to be able to serialize a Duration object (reference here) and have done so in my application. I have also tried implementing the custom serializer suggested in the reference above.

All other fields are de-serialized correctly, no matter the value.

An example of an instantiation of the DataClass can be:

DataClass(12345, "", Duration.hours(1))

What am I doing wrong here?

>Solution :

The Firebase Realtime Database can only store JSON values.

The Kotlin Duration class is not a known JSON type, and a quick code search on the SDK doesn’t show any special handling for the type.

In order to store a duration in the Firebase Realtime Database, you’ll have to keep it as a supported JSON type in your data class, or handle the conversions yourself.