Kotlin Dagger2 Error with Primary constructor

Question

I was trying my hand learning dagger 2, tried to convert the basic java example into kotlin but unable to do so because of the following error I am getting...

error: Dagger does not support injection into private fields private com.example.Engine engine;

Here is the Java code which is working fine,

public class Car {

    private Engine engine;
    private Wheel wheel;

    @Inject
    public Car(Engine engine, Wheel wheel) {
        this.engine = engine;
        this.wheel = wheel;
    }
}

Car.java class with having 2 dependency.

public class Engine {
    @Inject
    Engine(){}
}

public class Wheel {
    @Inject
    Wheel(){}
}

Here is my kotlin code :-

class Car(@Inject  var engine: Engine, @Inject  val wheels: Wheels) {
    fun drive(){
        Log.d("CAR","<<<<<< DRIVING >>>>>")
    }
}

class Engine @Inject constructor() {}

class Wheels @Inject constructor() {}

@Component
interface CarComponent {
    fun getCar() : Car
}

This is the generated code

public final class Car {
    @org.jetbrains.annotations.NotNull()
    @javax.inject.Inject()
    private com.toi.roboelectric.Engine engine;
    @org.jetbrains.annotations.NotNull()
    @javax.inject.Inject()
    private final com.toi.roboelectric.Wheels wheels = null;

    public final void drive() {
    }

    @org.jetbrains.annotations.NotNull()
    public final com.toi.roboelectric.Engine getEngine() {
        return null;
    }

    public final void setEngine(@org.jetbrains.annotations.NotNull()
    com.toi.roboelectric.Engine p0) {
    }

    @org.jetbrains.annotations.NotNull()
    public final com.toi.roboelectric.Wheels getWheels() {
        return null;
    }

    public Car(@org.jetbrains.annotations.NotNull()
    com.toi.roboelectric.Engine engine, @org.jetbrains.annotations.NotNull()
    com.toi.roboelectric.Wheels wheels) {
        super();
    }
}

Answer 1

Please update Car Class as

class Car @Inject constructor(var engine: Engine,val wheels: Wheels) {
fun drive(){
    Log.d("CAR","<<<<<< DRIVING >>>>>")
}