February 12, 2012

ACA: Extracting Text from a Style Name

In a recent reply post in the Getting steel beam size thread in the Autodesk AutoCAD® Architecture Discussion Group, Dallas asked if there was a way to automatically extract a value embedded in the name of a Structural Member Style. The specific example was if the style name were to include the shape size followed by the depth in parentheses: W16x45 (16.13).

I replied with a file attachment that had a sample file demonstrating that this was possible. The style-based StrMembStyles01 Property Set Definition, which applies to Structural Member Styles, in that file contains an Automatic property called Style that uses the Style automatic property source to make the style name available. The MemberDepth property uses the following VBScript code to extract the value between the parentheses in the style name and convert it to a real number:
styleName = "[Style]"
startChar = InStr( "[Style]",  "(" ) +1
endChar = InStr(  "[Style]",  ")" )
strLen = endChar - startChar

If strLen <= 0 Then
 memberDepth = 0
 memberDepth =  Mid( styleName, startChar, strLen )
End If

If Not IsNumeric( memberDepth ) Then
 memberDepth = 0
End If

RESULT = CDbl(memberDepth)
  1. The first line assigns the text string in the [Style] property to the variable styleName. As always, you cannot simply type or paste a property reference in a formula property. You have to insert them by placing your cursor in the upper left edit box and then double click the property in the list in the lower left box.
  2. The second line uses the VBScript InStr function to determine the position of the first character of the depth value embedded in the style name, which is presumed to be the first character after the first open parenthesis character, "(", found in the string. This is saved in the variable startChar.
  3. The third line also uses the InStr function to save the position of the first close parenthesis character, ")", to the variable endChar. In both the second and third lines, I probably should have used the styleName variable in lieu of additional references to the [Style] property.
  4. The fourth line assigns difference between startChar and endChar to the variable strLen, which is the length of the string that gives the member depth. Using the InStr function with delimiter characters avoids the need to have a fixed number of characters before the depth value and a fixed number of characters for the depth. The only requirement is that the first "(" character in the name immediately precede the depth value, and the first ")" character immediately follow the depth value.
  5. At this point, we have all of the information we need to get the string representing the member depth. If the Property Set gets attached to a Structural Member Style whose name is not properly formatted (no parentheses, first "(" is either preceded by or immediately followed by the first ")", one or more non-numeric characters between the first "(" and ")") and the resultant string is converted to a double precision number, an error will result. The formula property is set up to return a depth of 0 for improperly formatted style names. All of the mentioned error conditions except for non-numeric characters will result in a string length of 0 or less. The first If statement checks for this condition and sets variable memberDepth to 0 if true; otherwise it extracts the string between the first "(" and first ")".
  6. The second If statement tests the extracted string to verify it either is numeric or is a string that can be evaluated as numeric using the IsNumeric function, preceded by the Not operator. If the extracted string is not numeric, the value of memberDepth is reset to 0, otherwise, it is left as is.
  7. At this point, the value of memberDepth is either 0 or a numeric string, and can be converted to a double precision real number using the CDbl function. It is up to whatever additional use you make of this property to determine how to handle a value of 0.
Download the sample file attached to my post to see this formula property in action.

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