Room kotlin: Entities and Pojos must have a usable public constructor. Stuck on this error

Question

I am getting two error

• error: Fields annotated with @Relation cannot be constructor parameters. These values are fetched after the object is constructed.

• error: Fields annotated with @Relation cannot be constructor parameters. These values are fetched after the object is constructed.

I have two table. One is task table and other is sub-task table. For every entity of task table, there are some entities of subtask table.

So I am trying to get all the task and the list of subtask fro individual task

Dao:

@Query("Select * from TaskTable")
fun getTasks():List<TaskModel>

TaskModel:

class TaskModel(
        @Embedded
        var taskTable: TaskTable,

        @Relation(parentColumn = "id",
                entityColumn = "taskId")
        var subTaskTable: List<SubTaskTable>
)

TaskTable:

@Entity
data class TaskTable(
    @PrimaryKey(autoGenerate = true)
    var id:Int = 0,
    var taskListId:Int = 0,
    var title: String,
    var details:String?
)

SubTaskTable:

@Entity
data class SubTaskTable (
    @PrimaryKey(autoGenerate = true) var id: Int = 0,
    var taskId: Int = 0,

    var title: String,
    var details: String?)

build.gradle

//room
def room_version = "1.1.0"
implementation "android.arch.persistence.room:runtime:$room_version"
kapt "android.arch.persistence.room:compiler:$room_version"
// Test helpers
testImplementation "android.arch.persistence.room:testing:$room_version"

And I apply kotlin-kapt plugin

Help me to fix this problem. I search on stack overflow and implement some answer but this not fixed.

Answer 1

Well it says they shouldn't be constructor parameters, so try making them not constructor parameters.

class TaskModel() {
    @Embedded
    lateinit var taskTable: TaskTable

    @Relation(parentColumn = "id",
              entityColumn = "taskId")
    lateinit var subTaskTable: List<SubTaskTable>
}