Property: Difference between revisions

From FreeCAD Documentation
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Area
Area
Bool
Bool
BoolList
Color
Color
ColorList
ColorList
Direction
Distance
Distance
ElectricPotential
ElectricPotential
Enumeration
Enumeration
ExpressionContainer
ExpressionEngine
ExpressionEngine
File
File
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FloatConstraint
FloatConstraint
FloatList
FloatList
Font
Force
Force
Frequency
Frequency
Geometry
Integer
Integer
IntegerConstraint
IntegerConstraint
IntegerList
IntegerList
IntegerSet
Length
Length
Link
Link
LinkList
LinkList
LinkSubList
LinkSubList
Lists
Map
Material
Material
MaterialList
Matrix
Matrix
PartShape
PartShape
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Placement
Placement
PlacementLink
PlacementLink
PlacementList
Position
Precision
Pressure
Pressure
PythonObject
PythonObject
Quantity
QuantityConstraint
Rotation
Speed
Speed
Stiffness
Stiffness

Revision as of 15:21, 30 July 2022

Introduction

A property is a piece of information like a number or a text string that is attached to a FreeCAD document or an object in a document. Public properties can be viewed and modified in the Property editor.

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 PropertyLink:_InList_and_OutList

All property types

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

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"