Android Room Kotlin: entities with non data classes - function

Question

Regarding to classes that can/may be used for entities in room whith Kotlin,
Is it mandatory to use data classes? Or could I use 'normal classes', i.e., the ones I use for the 'bussiness logic'
In case data classes are mandatory: can I add functionality to what they have by default? i.e, can I add functions (for whatever taks they may need) to them?
The documentation doesn't say anything about limiting entities to data classes (although each and every code snippet use a data class).
Thanks.

Answer 1

Is it mandatory to use data classes?
No, you can use either including a mix.
data classes are a convenience class
can I add functionality to what they have by default?
Yes.
Perhaps consider the following:-
#Entity
class Table1 {
#PrimaryKey
var id: Long? = null
var name: String = ""
#Ignore
var notAColumnInTheTable = false
constructor(){}
#Ignore
constructor(name: String) {
this.id = null
this.name = name
this.notAColumnInTheTable = true
}
fun getIdAndName(): String {
return id.toString() + ":" + name
}
}
and :-
#Entity
data class Table2(
#PrimaryKey
var id: Long? = null,
var name: String,
#Ignore
var notAColumnInTheTable: Boolean = false
) {
constructor(name: String) : this( id = null,name = name, notAColumnInTheTable = true)
fun getIdAndName(): String {
return id.toString() + ":" + name
}
}
basically they are the same.
Using :-
#Dao
abstract class Table1And2Dao {
#Insert
abstract fun insert(table1: Table1): Long
#Insert
abstract fun insert(table2: Table2): Long
#Query("SELECT * FROM table1")
abstract fun getAllFromTable1(): List<Table1>
#Query("SELECT * FROM table2")
abstract fun getAllFromTable2(): List<Table2>
}
note the use of an abstract class rather than the normally see interface
along with a suitable #Database annotated class, in this case one that has a function that returns an instance of the built database and for convenience/brevity allows running on the main thread.
Then using :-
var db = AppDatabase.getDatabase(this)
var dao = db.getTable1AndTable2Dao()
dao.insert(Table1("TABLE1_1"))
dao.insert(Table2("TABLE2_1"))
for(t1: Table1 in dao.getAllFromTable1()) {
Log.d("DBINFO","Name is ${t1.name} ID is ${t1.id} NotAColumnInTable is ${t1.notAColumnInTheTable} idandname = ${t1.getIdAndName()}")
}
for(t2: Table2 in dao.getAllFromTable2()) {
Log.d("DBINFO","Name is ${t2.name} ID is ${t2.id} NotAColumnInTable is ${t2.notAColumnInTheTable} idandname = ${t2.getIdAndName()}")
}
Results in the log including:-
D/DBINFO: Name is TABLE1_1 ID is 1 NotAColumnInTable is true idandname = 1:TABLE1_1
D/DBINFO: Name is TABLE2_1 ID is 1 NotAColumnInTable is true idandname = 1:TABLE2_1
Via App Inspection :-
and :-