Question

I’m experimenting with ORMLite for android.

I have a pre built SQLite db that i am loading on the android device. I have stored position information as LocationX, LocationY columns:

CREATE TABLE graphicsinstances(Name STRING , LocationX FLOAT , LocationY FLOAT , SizeX FLOAT , SizeY FLOAT );

Catch is, at runtime i’d like this to look something like:

public class Vector2
{
    public float X;
    public float Y;
}
@DatabaseTable(tableName = "graphicsinstances")
public class graphicsinstance
{
    public GraphicalEntityInstance()
    {
        mName               = null;
        mPosition           = Vector2.zero();
        mSize               = Vector2.zero();
    }
    @DatabaseField(columnName = "Name", canBeNull = false)
    public String mName;

    //Olympic standard optimism
    //@DatabaseField(columnName = "Location", canBeNull = false)
    //public Vector2 mPosition;

    // current (unsatisfactory) method:
    @DatabaseField(canBeNull = false, useGetSet=true)
    private float LocationX;
    public float getLocationX() { return mPosition.X;}
    public void setLocationX(float x) { mPosition.X = x;}
    // repeat for Y, SizeX & SizeY!
}

Have I missed something obvious or am I completely barking up the wrong tree? can anyone suggest an alternative/prettier method?

Answer 1

If I understand, you want to map a table into a class with sub-classes. In your example I guess you want to load the LocationX and LocationY fields into the mposition which I guess is a Vector2?

I think it is ok to have a getMPosition() and setMPosition(mpos) methods that do the mapping between the LocationX and LocationY fields but you are not going to be able to do that mapping auto-magically with ORMLite.

---

From a purity standpoint I always recommend using what database circles call an “entity class”. This class mirrors your database structure exactly. It should have a one-to-one correspondence between fields in the table and the class. It can have methods like hashCode(), equals(), and the standard getter/setters but very little else.

You could create a wrapping object that takes a GraphicsInstance object in its constructor and does the Vector2 mapping and allows the other operations. When you are ready to persist it when you would need to go back to the GraphicsInstance object.