KF UG二次开发 里面函数 nx_askArcLength() 怎么用？

KF UG二次开发 里面函数 nx_askArcLength() 怎么用？
目的：选择线，测量选择线的长度，但是报错，函数自认为没问题，帮助看下。
代码：
(child) slect:
{
Class, %ui_comp_group;
title, "选择激光切割线测量线长";
Members, {len:};
};

(Child) len:
{
Class, %ui_comp_selection;
many, true;
SnapPointOverlay, false;
SoUpdateOption, 3;
Label, "选择曲线";
Tooltip, "选择激光切割曲线";
Scope, 1;
FilterTriple, {{3,0,0},{5,0,0},{9,0,0}};
SelectedObjects, {};
};

#计算曲线长度
(Number) lenth1: nx_askArcLength(len:SelectedObjects:);

以下为说明补充信息：

线长函数
函数: nx_askArcLength
描述: Returns the length of a given Curve/Edge
参数: curve (Any) Specify a curve
返回: (Number)- The length of a curve/edge

---

Returns the length of a given Curve/Edge

选择类说明：
DefClass: %ui_comp_selection (%ui_comp);

#+
Single/Multiple selection control

Single select   = False;
Multiple select = True;

#-
(Canonical boolean Parameter Modifiable) Many: true;

#+
SnapPointOverlay

This attribute allows the addition of point creation to
this selection component. If set to true, you have the option
of either selecting an existing object and/or creating a new point.
The point created will be added to the selectedObject list.

#-
(Canonical boolean Parameter Modifiable) SnapPointOverlay: false;

#+
SoUpdateOption

Smart Object Update Option

This attribute controls the update behavior of a point created
by using the SnapPointOverlay option.

UF_SO_dont_update = 0
UF_SO_update_within_modeling = 1
UF_SO_update_after_modeling = 2
UF_SO_update_after_parent_body = 3
#-
(Canonical integer Parameter Modifiable) SoUpdateOption: 3;

#+
The text for label
#-
(Canonical string Parameter Modifiable) Label: "Select Objects";

#+
The text for tooltip
#-
(Canonical string Parameter Modifiable) Tooltip: "Select Objects";

#+
Scope

Controls the selection scope for the object

UF_UI_SEL_SCOPE_WORK_PART 1 Allows you to select only objects
which belong to the work part.
This includes immediate
components of the work part. If
you select an object occurrence,
the prototype is returned.

UF_UI_SEL_SCOPE_ANY_IN_ASSEMBLY 3 Allows you to select any object
or object occurrence in the
assembly. No scope restrictions
are applied.

UF_UI_SEL_SCOPE_WORK_PART_AND_OCC 4 Allows you to select objects
which belong to the work part or
its subassembly. If you select
an object occurrence, the
prototype is returned.

UF_UI_SEL_SCOPE_WORK_PART_AND_WP_OCC 5 Allows you to select objects
which belong to the work part or
its subassembly. If you select
an object occurrence, the
occurrence of the work part is returned.
#-

(Canonical integer Parameter Modifiable) Scope: 1;

#+
The triple are a list of list in the format of {{type1, subtype1, feature_type1},
{type2, subtype2, feature_type2} ...}

type; - This can be one of the object types that are listed in
uf_object_types.h

subtype; - This can either be UF_all_subtype, or a proper
subtype of the object type selected

feature_type; - This is only meaningful when the object_type is
UF_solid_type. In that case, this should be set to
one of the solid feature type constants in uf_ui_types.h:

              FEATURE_ANY_EDGE               1
              FEATURE_LINEAR_EDGE            2
              FEATURE_CIRCULAR_EDGE          3
              FEATURE_ELLIPTICAL_EDGE        4
              FEATURE_INTERSECTION_EDGE      5
              FEATURE_BCURVE_EDGE            6
              FEATURE_SPCURVE_EDGE           7
              FEATURE_FOREIGN_EDGE           8
              FEATURE_CNST_PARM_EDGE         9
              FEATURE_ANY_WIRE_OR_EDGE      10
               
              FEATURE_ANY_FACE              20
              FEATURE_PLANAR_FACE           21
              FEATURE_CYLINDRICAL_FACE      22
              FEATURE_CONICAL_FACE          23
              FEATURE_SPHERICAL_FACE        24
              FEATURE_TOROIDAL_FACE         25
              FEATURE_PARAMETRIC_FACE       26
              FEATURE_BLENDING_FACE         27
              FEATURE_OFFSET_FACE           28
              FEATURE_SWEPT_FACE            29
              FEATURE_SWUNG_FACE            30
              FEATURE_FOREIGN_FACE          31
               
              FEATURE_ANY_COMPOSITE_BODY    32
              FEATURE_ANY_COMPOSITE_FACE    33
              FEATURE_ANY_COMPOSITE_EDGE    34

              FEATURE_SHEET_BODY            35
              FEATURE_SOLID_BODY            36 

For example, to enable selection of only elliptical edges and spherical faces of solids,
the list would be:

{
{ 70, 2, 24 }, #Spherical faces
{ 70, 3, 4 } #Elliptical edges
}
#-

(Canonical list Parameter Modifiable) FilterTriple: {};

#+
The list of selected objects
#-

(Canonical List Parameter Modifiable) SelectedObjects: {};
#+ @deprecated SelectedObject
please use SelectedObjects
#-
(Canonical List Parameter Modifiable) SelectedObject: SelectedObjects: ;

#+
The coordinates of the last pick point
#-

(Point modifiable ) PickPoint: point(0,0,0);

#+
The view of the last pick point
#-
(Any modifiable ) PickView: ;

(String) ClassName: "UGS::UI::Comp::KFselectObject";

这个看看有没有用
https://b23.tv/PXgY6MQ