Add custom property to panel

Question

I created a custom property for my armature and I want to add it to my custom panel. If I want to add an object property to a panel I'll do it like this layout.prop(object, "property"). However this doesn't work for custom properties that I created. What am I doing wrong?

I'm using Blender version 2.79.

Here is the panel code:

class MyPanel(bpy.types.Panel):
    bl_space_type = "VIEW_3D"
    bl_region_type = "TOOLS"
    bl_label = "MyPanel"
    bl_category = "MyPanel"

    def draw(self, context):
       layout = self.layout
       object = context.object

       layout.prop(object, "prop") #Custom property is called "prop"

Answer 1

The custom property is not accessed as an attribute with the ., but through the name of the property.

bpy.data.objects["Armature"]["prop"]

Therefore the correct way of adding the property is:

layout.prop(bpy.data.objects["Armature"], '["prop"]')

You can add your custom property like this:

import bpy

class MyPanel(bpy.types.Panel):
    bl_space_type = "VIEW_3D"
    bl_region_type = "TOOLS"
    bl_label = "MyPanel"
    bl_category = "MyPanel"

    def draw(self, context):
        layout = self.layout
        layout.prop(bpy.data.objects["Armature"], '["prop"]')


classes = (MyPanel,)


def register():
    for cls in classes:
        bpy.utils.register_class(cls)


def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)

if __name__ == "__main__":
    register()

Answer 2

First, assign "foobar" to an object:

obj["foobar"] = 3

then in a panel draw() function:

layout.prop(obj, f'["{bpy.utils.escape_identifier("foobar")}"]')

Also note: It appears the syntax is sensitive to the use of inner quoations - there have to be single double quotes " inside the bracket, single quotes ' or triple double/single quotes """/''' wont work

---

Previous answer by Robert appears to be non-functioning in Blender 3.6.2 Hash: e53e55951e7a. To get it to run without errors during registration, you have to remove the line:

bl_category = "MyPanel"

and even then you get:

rna_uiItemR: property not found: Object.["prop"]