Classes extending wrappers

[gswifort]

I want to create classes that extend your wrappers, e.g. something like this:

from pyrx import Db, Ed, command


class BlockReference(Db.BlockReference):
    def attributes(self) -> dict[str, Db.AttributeReference]:
        return {
            attr.tag(): attr 
            for attr in (Db.AttributeReference(id) for id in self.attributeIds())
        }


# usage:

@command
def doit():
    status, bref_id, point = Ed.Editor.entSel(
        "Select a block reference:", Db.BlockReference.desc()
    )
    if not status == Ed.PromptStatus.eOk:
        return
    bref = BlockReference(bref_id)
    print(bref.attributes())


# {
#   'ATTR1': <PyDb.AttributeReference object at 0x0000013DDD0888B0>,
#   'ATTR2': <PyDb.AttributeReference object at 0x0000013DDD088860>
# }

Is this a good way? Do you see any risks?

[CEXT-Dan]

it’s great! no risk I’m aware of, I used to do that a lot in .NET before extension methods came out.

[gswifort]

Is there any way to return wrappers as an object of an extending class?

Suppose I have implemented a class:

# pyrx/db/extents.py
class Extents(Db.Extents):
    ...

Is there any possibility that Db.Entity.getGeomExtents() returns pyrx.db.extents.Extents instance?

[CEXT-Dan]

I think that would be a can of worms in C++, I would have to use the same approach as wxWidgets and link with the C++ library, I'd rather not. The exception would be numpy as there’s already boost::python::numpy, but even there, I don’t want to create versioning conflicts

Note, Db.Extents would actually be a cuboid, with its X,Y,Z edges always aligned WCS. If your entity is rotated in 3d space, you have transform the object to WCS before you call getGeomExtents, it’s not a good match shapely.Polygon

I think this is better done in the programmers application rather than in the API

[gswifort]

I understand, Extents was just an example, maybe not the best. Let's leave it open, maybe some ideas will come.

[CEXT-Dan]

How best to interface with other popular Python packages is a worthy discussion to have. Example AcDbTable <--> Pandas dataframe, Point3d <--> np.array i.e. for pykdtree, and of course shapely. I did spend some time on Db.Polyline so it works with a variety of collections. Ge.Point3d should work with networkx

[gswifort]

I think I will create classes that will be able to take an object from c++ and wrap it (treat it as self)

[gswifort]

This is probably a really bad idea, but it works:

from pyrx import Db, Ed, command


class WrapperMeta(type(Db.Extents)):
    def __call__(cls, *args, **kwds):
        if args and isinstance(args[0], cls.__base__):
            assert len(args) == 1
            assert len(kwds) == 0
            obj = args[0]
            obj.__class__ = cls  # this is where all the magic is
            return obj
        else:
            return super().__call__(*args, **kwds)


class xExtents(Db.Extents, metaclass=WrapperMeta):
    def meth(self):
        print("xExtents.meth")


@command
def demo():
    status, ent_id, _ = Ed.Editor.entSel("Select: ")
    if not status == Ed.PromptStatus.eOk:
        return
    ent = Db.Entity(ent_id)
    ext = ent.getGeomExtents()
    print(ext)
    ext2 = xExtents(ext)
    print(ext2)
    ext2.meth()
    print(xExtents())