November 05, 2019

ACA-AMEP: Edit Property Data Via AutoLISP, Part 2

First article in the series.

In the previous article, we obtained a collection of the Property Sets on the object for which we want to change the value of a Property. We also determined the total number of Property Sets in the collection, and set up a Property Set counter, initialized to 0, the index of the first Property Set. The following code assumes that you know not only the name of the Property that is to be changed, but also the name of the Property Set in which it resides and that the name is stored in a variable called sPSet.
(while (< iPSet iPSets)  ; While unprocessed Property Sets remain...
  (setq oPSet   (vlax-invoke-method oPSets 'Item iPSet) ; Get current Property Set object.
        sPSetNm (vlax-get-property oPSet 'Name)         ; Get Property Set name.
  ) ;_ End setq.
  (if (= (strcase sPSetNm) (strcase sPSet))             ; If target Property Set is found...
    (setq iPSet (1+ iPSets))                            ; ...exit while loop.
    (setq iPSet (1+ iPSet))                             ; ...else, increment Property Set counter.
  ) ;_ End if.
) ;_ End while.

Here is what is happening in that code:
  • A while loop is used to iterate over the Property Sets collection. The Item method is used to get the Property Set at the current index value in iPSet.
  • The Name property of the Property Set object is used to obtain the name of that Property Set.
  • An if statement is used to determine if that Property Set name matches the target Property Set name. The strcase function is used to change both strings to all capital letters, to avoid any issues with different capitalization of the names. If a match is found, the iPSet index counter is set to a number one greater than the total numnber of Property Sets in the collection, so that the loop will be exited. If a match is not found, the iPSet index counter is incremented by 1, so that the next Property Set in the collection will be processed on the next pass of the loop, if at least one unprocessed Property Set remains.

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