Draft and Arch objects TypeId

[carlopav]

Hello, maybe it is a stupid question. Why Draft and Arch objects have not a TypeId property? something like Part::Box or Sketcher::Sketch ... so Draft::Line or Draft::Circle ?

[DeepSOIC]

They do, sorta. Use Draft.getType. The standard TypeId doesn't help much because it is a C++ thing only.
https://forum.freecadweb.org/viewtopic. ... 18#p135051

[vocx]

Hello, maybe it is a stupid question. Why Draft and Arch objects have not a TypeId property? something like Part::Box or Sketcher::Sketch ... so Draft::Line or Draft::Circle ?

Most Draft objects are created from a Part::Part2DObject, which is "a specialized version of the PartShape for use with flat (2D) geometry", according to src/Mod/Part/App/Part2DObject.h.

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def makeCircle(radius, placement=None, face=None, startangle=None, endangle=None, support=None):
    ...
    obj = FreeCAD.ActiveDocument.addObject("Part::Part2DObjectPython",n)
    _Circle(obj)

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obj = Draft.makeCircle(100)
>>> obj.TypeId
'Part::Part2DObjectPython'

The constructor class _Wire, or _Circle, or whatever, is normally derived from _DraftObject, which defines a Proxy attribute, which holds a reference to the class that was used to create the object.

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>>> obj.Proxy
<Draft._Circle object at 0x7fd4eb98fdd8>

The class has a Type attribute that you can investigate and set.

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>>> obj.Proxy.Type
'Circle'

obj.Proxy.Type = "Banana"
>>> obj.Proxy.Type
'Banana'

So, basically, what Draft.getType() does, is to check the obj.Proxy.Type (for Python objects), or the obj.TypeId (for C++ objects).

In the case of Arch, objects are derived from Part::Feature, and the constructor, for example, _ArchPipe, similarly sets the Type to something like "Pipe".

[carlopav]

Thanks, really clear now.

[yorik]

The TypeId is important so you know the base C++ class of your object. The python objects such as Drafts, Archs, etc... are actually live python objects that live inside the C++ object's Proxy property. So it makes sense that the TypeId always refers to the "carrier" C++ object.

The idea of having a Type attribute inside the Proxy object was a dirty hack at first, but it has been more and more used all over FreeCAD (in FEM, Path, etc..) so it has now more or less become a norm now... Be careful of the dirty hacks you do, they might become the norm one day