Selecting all objects that have been specified in Modifiers

Question

Could anyone help in making a script for selecting all objects that are specified in the different modifiers that an object has stacked? For example if my object has a Boolean modifier and an Array modifier, which both refer to an empty or another object (in the Array modifier there is for example an Object offset you can specify). Would it be possible to select all those object with one click? Thanks.

Answer 1

Using the bl_rna.properties collection. This gives the name, type and other properties of the properties of the modifier. If the property is an object it is most likely, both a PointerProperty (prop.type == 'POINTER') and points to a prop.fixed_type of bpy.types.Object. If so getattr(modifier, propertyname) will be either the object if set, or None if not.

import bpy
context = bpy.context
obj = context.object
for m in obj.modifiers:
    print("modifier (%s): %s" % (m.type, m.name))
    for k, v in m.bl_rna.properties.items():
        if v.type == 'POINTER' and v.fixed_type.name == "Object":
            print("\t", k, getattr(m, k))
            # select mod obj if not None
            ob = getattr(m, k, None)
            if ob is not None:
                ob.select_set(True)

Answer 2

It is a little brute-force, but here is my attempt : http://web.purplefrog.com/~thoth/blender/python-cookbook/select-objects-in-modifiers.html

import bpy
import inspect

def select_objects_in_modifiers(obj):
    rna = obj.bl_rna

    refs = set()
    for mod in obj.modifiers:
        for key,val in inspect.getmembers(mod):
            if val is None:
                continue
            if hasattr(val, "bl_rna") and val.bl_rna == rna:
                refs.add(val)

    for o2 in refs:
        o2.select = True
        #print(o2)


select_objects_in_modifiers(bpy.context.active_object)

We use inspect.getmembers to scan all the fields of a modifier and check to see if the .bl_rna matches the bl_rna for an object. If so, that must be an object referenced by a modifier.