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Введение

Свойство - это доля информации вроде числа или строки текста, прилагаемая к документу FreeCAD или объекту в нём. Свойства могут быть просмотрены и - если это разрешено - изменены с помощью редактора свойств.

Свойства играю важную роль в FreeCAD, поскольку он с самого начала создан для работы с параметрическими объектами, которые есть объекты, определяемые только их свойствами.

Пользовательские параметрические объекты в FreeCAD могут обладать свойствами следующих типов: 

 Boolean
Float
FloatList
FloatConstraint
Angle
Distance
Integer
IntegerConstraint
Percent
Enumeration
IntegerList
String
StringList
Link
LinkList
Matrix
Vector
VectorList
Placement
PlacementLink
Color
ColorList
Material
Path
File
FileIncluded
PartShape
FilletContour
Circle

Properties play a very important role in FreeCAD. As objects in FreeCAD are "parametric", this means that their behavior is defined by their properties, and how these properties are used as input for their class methods. See also FeaturePython Custom Properties and PropertyLink: InList and OutList

All property types

Custom scripted objects can use any of the property types defined in the base system:

Name Unit (if any) Remark
Acceleration m/s^2
AmountOfSubstance mol
Angle °
Area m^2
Bool
BoolList
Color
ColorList
CurrentDensity A/m^2 introduced in 0.21
Density kg/m^3
Direction
DissipationRate m^2/s^3 introduced in 0.21
Distance m
DynamicViscosity Pa*s introduced in 0.21
ElectricalCapacitance F introduced in 0.21
ElectricalConductance S introduced in 0.21
ElectricalConductivity S/m introduced in 0.21
ElectricalInductance H introduced in 0.21
ElectricalResistance Ohm introduced in 0.21
ElectricCharge C introduced in 0.21
ElectricCurrent A introduced in 0.21
ElectricPotential V introduced in 0.20
Enumeration
ExpressionEngine
File
FileIncluded
Float
FloatConstraint
FloatList
Font
Force N
Frequency Hz
HeatFlux W/m^2 introduced in 0.21
Integer
IntegerConstraint
IntegerList
IntegerSet
InverseArea 1/m^2 introduced in 0.21
InverseLength 1/m introduced in 0.21
InverseVolume 1/m^3 introduced in 0.21
KinematicViscosity m^2/s introduced in 0.21
Length m
Link
LinkChild
LinkGlobal
LinkHidden
LinkList
LinkListChild
LinkListGlobal
LinkListHidden
LinkSub
LinkSubChild
LinkSubGlobal
LinkSubHidden
LinkSubList
LinkSubListChild
LinkSubListGlobal
LinkSubListHidden
LuminousIntensity cd introduced in 0.21
MagneticFieldStrength A/m introduced in 0.21
MagneticFlux Wb or V*s introduced in 0.21
MagneticFluxDensity T introduced in 0.21
Magnetization A/m introduced in 0.21
Map
Mass kg introduced in 0.21
Material
MaterialList
Matrix
PartShape a Part property, is accessed as
Part::PropertyPartShape
Path
Percent
PersistentObject
Placement
PlacementLink
PlacementList
Position
Power W introduced in 0.21
Precision
Pressure Pa
PythonObject
Quantity
QuantityConstraint
Rotation
ShearModulus Pa introduced in 0.21
SpecificEnergy m^2/s^2 or J/kg introduced in 0.21
SpecificHeat J/kg/K introduced in 0.21
Speed m/s
Stiffness m/s^2
Stress Pa introduced in 0.21
String
StringList
Temperature K introduced in 0.21
ThermalConductivity W/m/K introduced in 0.21
ThermalExpansionCoefficient 1/K introduced in 0.21
ThermalTransferCoefficient W/m^2/K introduced in 0.21
Time s introduced in 0.21
UltimateTensileStrength Pa introduced in 0.21
UUID
VacuumPermittivity s^4*A^2 / (m^3*kg)
Vector
VectorDistance
VectorList
Velocity m/s introduced in 0.21
Volume l or m^3
VolumeFlowRate l/s or m^3/s introduced in 0.21
VolumetricThermalExpansionCoefficient 1/K introduced in 0.21
Work J introduced in 0.21
XLink
XLinkList
XLinkSub
XLinkSubList
YieldStrength Pa introduced in 0.21
YoungsModulus Pa introduced in 0.21

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:

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"


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