topic Re: Create a Field Formula from Field Expressions in Visual LISP, AutoLISP and General Customization Forum

Create a Field Formula from Field Expressions

Julio_Soto — Mon, 18 Aug 2025 15:42:57 GMT

I have a lisp that I'm writing that takes a length parameter from a dynamic block and divides it by the unit factor (for dwg with different units)

when I do this manually in AutoCAD the field looks like this

%<\AcExpr (%<\_FldPtr 1947961495696>% / %<\_FldPtr 1947961496080>%) \f "%lu2%zs12">%

but each FldPtr looks like this
%<\AcObjProp.16.2 Object(%<\_ObjId 1948028287920>%).Parameter(1).UpdatedDistance \f "%lu6%zs12">%

and
%<\AcObjProp.16.2 Object(%<\_ObjId 1948028287920>%).InsUnitsFactor \f "%lu6%zs12">%

I can get those two fields with Lee-Mac's getobject Id and pramters, ect. but I don't know how to build the FldPtr expressions.

is this possible with LISP?

Re: Create a Field Formula from Field Expressions

paullimapa — Mon, 18 Aug 2025 17:00:04 GMT

did you create this field using the field formula option?

%<\_FldPtr 1947961496080>%)

Re: Create a Field Formula from Field Expressions

Julio_Soto — Mon, 18 Aug 2025 17:47:09 GMT

Yes. I used the "Formula" option, then in the window where you enter formulas I create two more fields.

I can create each field just fine with AutoLISP, but I dont' know how to create a FldPtr that AutoCAD uses, like this
%<\AcExpr (%<\_FldPtr 1947961495696>% / %<\_FldPtr 1947961496080>%) \f "%lu2%zs12">%

each field was assigned some ID by autocad.

Those FldPtr are referencing the other two fields.

Re: Create a Field Formula from Field Expressions

paullimapa — Mon, 18 Aug 2025 18:18:00 GMT

In place of both: %<\_FldPtr 1947961495696>% and %<\_FldPtr 1947961496080>%

use the actual %<\AcObjProp reference which would be something like this:

(strcat "%<\\AcExpr " "(" %<\\AcObjProp.16.2 Object(%<\\_ObjId 1948028287920>%).Parameter(1).UpdatedDistance \\f \"%lu6%zs12\">%" " / " "%<\\AcObjProp.16.2 Object(%<\\_ObjId 1948028287920>%).InsUnitsFactor \\f \"%lu6%zs12\">%" ")" "\\f \"%lu6%zs12\">%" )

Re: Create a Field Formula from Field Expressions

Julio_Soto — Mon, 18 Aug 2025 19:26:58 GMT

i was tying something similar but this is the MTEXT output

This is my test code, with the ObjectID hardcoded into the lisp for testing. also attached is the block i'm working with.

(defun c:TestBoltLengthField (/ pt objId paramId str) (setq pt (getpoint "\nPick insertion point for test field: ")) (setq str (strcat "%<\\AcExpr " "(" "%<\\AcObjProp.16.2 Object (%<\\_ObjId 2429014325728).Parameter(1).UpdatedDistance \\f \"%lu6%zs12\">%" " / " "%<\\AcObjProp.16.2 Object(%<\\_ObjId 2429014325728).InsUnitsFactor \\f \"%lu6%zs12\">%" ")" "\\f \"%lu6%zs12\">%" ) ) ;; Insert it as MText (entmakex (list '(0 . "MTEXT") '(100 . "AcDbEntity") '(100 . "AcDbMText") (cons 10 pt) (cons 40 0.2) ;; text height (cons 1 str) ;; the field string (cons 7 "Arial") (cons 71 1) ;; top-left attachment (cons 72 5) ;; L-to-R flow (cons 11 (list 1.0 0.0 0.0)) (cons 210 (list 0.0 0.0 1.0)) ) ) (princ) ) (princ "\nTest TEst")

Re: Create a Field Formula from Field Expressions

paullimapa — Mon, 18 Aug 2025 21:57:59 GMT

Don't think you can hardcode the ObjectID.

So I would use this function to get it and convert it from integer to string:

(itoa (vla-get-objectid obj))

Then the complete string formatting will look like this:

(setq str (strcat "%<\\AcExpr " "(" "%<\\AcObjProp.16.2 Object(%<\\_ObjId " (itoa (vla-get-objectid obj)) ">%).Parameter(90).lookupString \\f \"%lu6%zs12\">%" " / " "%<\\AcObjProp.16.2 Object(%<\\_ObjId " (itoa (vla-get-objectid obj)) ">%).InsUnitsFactor \\f \"%lu6%zs12\">%" ")" " \\f \"%lu6%zs12\"" ">%" ) )

Now you can't add the string into the MText object when you create it so I would keep the string empty like this:

(entmakex (list '(0 . "MTEXT") '(100 . "AcDbEntity") '(100 . "AcDbMText") (cons 10 pt) (cons 40 0.2) ;; text height ; (cons 1 str) ;; the field string (cons 1 "") (cons 7 "Arial") (cons 71 1) ;; top-left attachment (cons 72 5) ;; L-to-R flow (cons 11 (list 1.0 0.0 0.0)) (cons 210 (list 0.0 0.0 1.0)) ) )

Then use this vla function to put the text in:

(vla-put-textstring (vlax-ename->vla-object (entlast)) str)

Now editing the MText Field object, it does show both numerator and denominator:

But it still evaluates to ### because of the mm unit string that comes with the 65.

Re: Create a Field Formula from Field Expressions

Julio_Soto — Mon, 18 Aug 2025 22:05:42 GMT

so if you double click the field "65mm" you'll see the other to fields

the "mm" is just from "Additional formatting"

aside fromthe 65mm you were able to get it to work?

Re: Create a Field Formula from Field Expressions

paullimapa — Mon, 18 Aug 2025 22:10:48 GMT

yes, the fields do show up when I run the codes I provided you in my previous post

Re: Create a Field Formula from Field Expressions

Julio_Soto — Mon, 18 Aug 2025 22:50:00 GMT

Thanks for the help dude, this is the code that is working right

(defun c:TestBoltLengthField (/ pt blkObj objectID str mtextEnt) (setq pt (getpoint "\nPick insertion point for test field: ")) (setq obj (vlax-ename->vla-object (car (entsel "\nSelect block: ")))) (setq objectID (getobjectid obj)) ;; Lee Mac helper ;; Build field string (setq str (strcat "%<\\AcExpr " "(" "%<\\AcObjProp.16.2 Object(%<\\_ObjId " objectID ">%).Parameter(1).UpdatedDistance \\f \"%lu6%zs12\">%" " / " "%<\\AcObjProp.16.2 Object(%<\\_ObjId " objectID ">%).InsUnitsFactor \\f \"%lu6%zs12\">%" ")" " \\f \"%lu2%zs12\"" ">%" ) ) ;; Insert dummy MTEXT (setq mtextEnt (entmakex (list '(0 . "MTEXT") '(100 . "AcDbEntity") '(100 . "AcDbMText") (cons 10 pt) (cons 40 0.2) ;; text height (cons 1 "-") ;; placeholder (cons 7 "Arial") (cons 71 1) ;; top-left attachment (cons 72 5) ;; L-to-R flow (cons 11 (list 1.0 0.0 0.0)) (cons 210 (list 0.0 0.0 1.0)) ) ) ) (vla-put-TextString (vlax-ename->vla-object mtextEnt) str) (princ) ) (defun GetObjectID (BlockVLA / acadobj acaddoc BlockEname BlockVLA) (setq acadobj (vlax-get-acad-object) acaddoc (vla-get-activedocument acadobj) ) ;; Lee Mac (if (eq "X64" (strcase (getenv "PROCESSOR_ARCHITECTURE"))) (vlax-invoke-method (vla-get-Utility acaddoc) 'GetObjectIdString BlockVLA :vlax-false) (itoa (vla-get-Objectid BlockVLA)) ) )

in addition to some formatting issue, my main problem was putting my string in ENTMAKEX. using vla-put-TextString was the trick. thanks again my friend!

(also i used lee-mac getobjectID)

Re: Create a Field Formula from Field Expressions

paullimapa — Mon, 18 Aug 2025 22:58:58 GMT

you are welcome...cheers!!!