Expression access to "children" differs between container objects

[krushia]

Is there an existing issue for this?

• I have searched the existing issues

Problem description

Writing an expression to access a child of a container is over-complicated because containers use different properties to list children. All of the following objects use an App::PropertyLinkList with a different name for grouping children.

The obvious containers:

• Group in App::DocumentObjectGroup, App::Part
• ElementList in App::LinkGroup

Some not so obvious containers:

• Group in PartDesign::Body
• Links in Part::Compound
• Objects in the Part::FeaturePython BOPTools.JoinFeatures.FeatureConnect and draftobjects.clone.Clone
• OriginFeatures in App::Origin
• Shapes in Part::MultiFuse
• Views in TechDraw::DrawPage

There are others not listed.

Now, assuming I want an expression that selects the first "child" in a container, I must use an absurd chain of conditionals to be flexible. Here is a partial example from my current project, where <<ClipStripConfig>>.Configuration_Preset is an App::PropertyXLink that the user sets to point to a container (ideally of any type they prefer) that is expected to have a first child be a spreadsheet.

<<ClipStripConfig>>.Configuration_Preset.TypeId == <<App::DocumentObjectGroup>> ? <<ClipStripConfig>>.Configuration_Preset.Group[0] : <<ClipStripConfig>>.Configuration_Preset.TypeId == <<App::Part>> ? <<ClipStripConfig>>.Configuration_Preset.Group[0] : <<ClipStripConfig>>.Configuration_Preset.TypeId == <<App::LinkGroup>> ? <<ClipStripConfig>>.Configuration_Preset.ElementList[0] : False

There is of course OutList, but it also contains objects referenced by property expressions, so is of no use. What we need is a universal name that can be used to list ordered children of any container. Perhaps call it Children?

Full version info

OS: Gentoo Linux (KDE/plasma)
Word size of FreeCAD: 64-bit
Version: 0.22.0dev.37358 (Git) AppImage
Build type: Release
Branch: main
Hash: 3a0152b076dd7791c9724c286963d74b5814e24f
Python 3.11.9, Qt 5.15.13, Coin 4.0.2, Vtk 9.2.6, OCC 7.7.2
Locale: English/United States (en_US)
Installed mods: 
  * parts_library
  * Curves 0.6.36
  * A2plus 0.4.64a
  * DynamicData 2.62.0
  * Assembly4 0.50.12 (Disabled)
  * Alternate_OpenSCAD 1.0.0 (Disabled)
  * CurvedShapes 1.0.9
  * fasteners 0.5.20
  * SearchBar 1.0.2
  * Nodes 0.1.36 (Disabled)
  * 3D_Printing_Tools
  * workfeature
  * MnesarcoUtils 0.2.5
  * OpenTheme 2024.5.3
  * Manipulator 1.5.7
  * Assembly3 0.12.2
  * lattice2 1.0.0
  * Launcher
  * CommandPanel
  * CubeMenu
  * Reinforcement
  * PieMenu 1.5.0
  * MeshRemodel 1.9.23

Subproject(s) affected?

Core

Anything else?

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[kaiwas]

Perhaps call it Children?

Great offer. I would also like to add that the “parent”-“children” connection under ideal conditions should work in both directions. Perhaps call it Parent?
But right now it only works from parent to child. (Otherwise the problem of circular dependency arises)
Perhaps this is a “system” limitation and cannot be implemented. But if we manage to do this, it would be a revolution!

For example.
Now I can make the height of the window depend on the height of the wall in which it is built.
But I can't make the wall height change if I change the window height. (only possible when using spreadsheets or “third-party” control objects. But this is sometimes an unnecessary entity).

[Roy-043]

Are you aware of the OutList property?