Objekteigenschaften

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Revision as of 08:35, 18 January 2023 by FBXL5 (talk | contribs)

Einleitung

Eine Eigenschaft ist eine Information in Form einer Zahl oder einer Zeichenkette, die mit einem FreeCAD-Dokument oder einem Objekt in einem Dokument verbunden ist. Öffentliche Eigenschaften können mit dem Eigenschaftseditor angezeigt und geändert werden.

Eigenschaften spielen in FreeCAD eine sehr wichtige Rolle. Objekte in FreeCAD sind "parametrisch", d.h. ihr Verhalten wird durch ihre Eigenschaften festgelegt, die als Eingangsgrößen für ihre Klassenmethoden genutzt werden. Siehe auch FeaturePython Custom Properties and PropertyLink: InList and OutList

Alle Arten von Eigenschaften

Benutzerdefinierte skriptgenerierte Objekte können jede Arten der Eigenschaften verwenden, die im Basis-System definiert sind:

Acceleration
Angle
Area
Bool
BoolList
Color
ColorList
Direction
Distance
ElectricPotential
Enumeration
ExpressionContainer
ExpressionEngine
File
FileIncluded
Float
FloatConstraint
FloatList
Font
Force
Frequency
Geometry
Integer
IntegerConstraint
IntegerList
IntegerSet
Length
Link
LinkList
LinkSubList
Lists
Map
Material
MaterialList
Matrix
PartShape
Path
Percent
Placement
PlacementLink
PlacementList
Position
Precision
Pressure
PythonObject
Quantity
QuantityConstraint
Rotation
Speed
Stiffness
String
StringList
VacuumPermittivity
Vector
VectorDistance
VectorList
Volume

Internally, the property name is prefixed with App::Property:

App::PropertyBool
App::PropertyFloat
App::PropertyFloatList
...

Remember that these are property types. A single object may have many properties of the same type, but with different names.

For example:

obj.addProperty("App::PropertyFloat", "Length")
obj.addProperty("App::PropertyFloat", "Width")
obj.addProperty("App::PropertyFloat", "Height")

This indicates an object with three properties of type "Float", named "Length", "Width", and "Height", respectively.

Scripting

See also: FreeCAD scripting basics

A scripted object is created first, and then properties are assigned.

obj = App.ActiveDocument.addObject("Part::Feature", "CustomObject")

obj.addProperty("App::PropertyFloat", "Velocity", "Parameter", "Body speed")
obj.addProperty("App::PropertyBool", "VelocityEnabled", "Parameter", "Enable body speed")

In general, Data properties are assigned by using the object's addProperty() method. On the other hand, View properties are normally provided automatically by the parent object from which the scripted object is derived.

For example:

  • Deriving from App::FeaturePython provides only 4 View properties: "Display Mode", "On Top When Selected", "Show In Tree", and "Visibility".
  • Deriving from Part::Feature provides 17 View properties: the previous four, plus "Angular Deflection", "Bounding Box", "Deviation", "Draw Style", "Lighting", "Line Color", "Line Width", "Point Color", "Point Size", "Selectable", "Selection Style", "Shape Color", and "Transparency".

Nevertheless, View properties can also be assigned using the view provider object's addProperty() method.

obj.ViewObject.addProperty("App::PropertyBool", "SuperVisibility", "Base", "Make the object glow")

Source code

In the source code, properties are located in various src/App/Property* files.

They are imported and initialized in src/App/Application.cpp.

#include "Property.h"
#include "PropertyContainer.h"
#include "PropertyUnits.h"
#include "PropertyFile.h"
#include "PropertyLinks.h"
#include "PropertyPythonObject.h"
#include "PropertyExpressionEngine.h"