Db.Database.addObject(<Entity>) throws eWrongObjectType

[gswifort]

from __future__ import annotations

from pyrx import Ap, Db, Ed, Ge, command

@command
def doit2():
    db = Db.curDb()
    line = Db.Line()
    db.addObject(line)

causes

    db.addObject(line)
PyDb.ErrorStatusException: Exception!(eWrongObjectType), function addAcDbObject, Line 651, File PyDbDatabase.cpp:

is this expected behavior?

[CEXT-Dan]

Yes, it’s not for entities , the intention is to add an object like a dictionary to the database and get an object Id. The object is not assigned an owner, so you have to give it one, like another dictionary. Objects with no owners are not saved with the drawing

Only BlockTableRecords can be owners of drawable entities

[gswifort]

zwcad doesn't have this limitation. Is this a limitation of the AutoCAD API? I don't see this information in the documentation. Adding an object to the database is useful when creating a block reference. Otherwise, the block creating the reference must know which BTR the reference should be added to.

[CEXT-Dan]

That would be a bug in ZwCAD as undefined behavior, this is from the C++ header file
I can add eWrongObjectType in the ZwCAD port

 /// <summary>
 /// Adds a currently non-resident AcDbObject to this database.
 /// </summary>
 /// <param name="id"> Receives the object's new id on success, else null </param>
 /// <param name="pObj"> Pointer to an object which is not yet database resident</param>
 /// <returns> eOk on success, otherwise an error code </returns>
 /// <remarks> Does not set the object's owner, and does not close the object
 ///           Fails with eWrongObjectType if *pObj derives from AcDbEntity
 /// </remarks>
 ///

[gswifort]

I can add eWrongObjectType in the ZwCAD port

I'll leave that to your discretion. I've often used this mechanism in the scenario described above. Sometimes I create blocks temporarily and ultimately don't want to store them in the database—is there a better way?

[CEXT-Dan]

I’ll leave it. I think there’s a couple of tricks, I.e. you can use a temporary anonymous block (named *U), then use DbObject::swapIdWith, then erase() the temporary. Maybe use a RAII-like resource manager or Context Manager to call erase on the temp.

[gswifort]

then use DbObject::swapIdWith

I've never used this before, I'll have to test it out. Thank you.