Property

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Introduction

En egenskap är en informationsbit som till exempel ett nummer eller en textsträng som hör till ett FreeCAD dokument eller ett objekt i ett dokument. Egenskaper kan visas och - om det är tillåtet - ändras med egenskapsredigeraren.


Egenskaper spelar en mycket viktig roll i FreeCAD, eftersom det från början är gjort för att arbeta med parametriska objekt, vilket är objekt som endast definieras av deras egenskaper.


Anpassade skript objekt i FreeCAD kan ha egenskaper av följande typer:


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.

All property types

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

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

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")