CONTROLLING LAYERS AND LINETYPES in Word

Creator QR in Word CONTROLLING LAYERS AND LINETYPES

In some situations your program must determine if an element is present in the collection. One way to do this is to search for the element while iterating the collection, as described earlier in the chapter. The following example gets a linetype name from the user and then checks for its existence by iterating the Linetypes collection: Public Sub CheckForLinetypeByIteration() Dim objLinetype As AcadLineType Dim strLinetypeName As String strLinetypeName = InputBox("Enter a Linetype name to search for: ") If "" = strLinetypeName Then Exit Sub ' exit if no name entered For Each objLinetype In ThisDrawing.Linetypes If 0 = StrComp(objLinetype.Name, strLinetypeName, vbTextCompare) Then MsgBox "Linetype '" & strLinetypeName & "' exists" Exit Sub ' exit after finding linetype End If Next objLinetype MsgBox "Linetype '" & strLinetypeName & "' does not exist" End Sub Unlike prior releases, in which linetype names were converted to uppercase, AutoCAD 2000 and later allow the names to be a mix of upper- and lowercase, although Linetype1 and LINETYPE1 will be treated as the same name. This sample uses a case-insensitive string comparison of strLinetypeName and each Linetype name to allow for capitalization differences. A second technique is to let AutoCAD perform the search for you. This is quite a bit more efficient because AutoCAD can internally determine if the element is present, and it eliminates sending unneeded elements to your program. AutoCAD will also handle the case-insensitive name comparison for you. To use this technique you must employ the VBA error handler. Like many AutoCAD ActiveX objects, the Linetypes collection uses run-time errors or exceptions to signal unexpected conditions. If an exception isn t handled, the calling program halts and displays an error message to the user. In this case, Linetypes will raise an exception if you attempt to access an unknown Linetype name. By detecting this exception, or more correctly the lack of the exception, your program is notified of the existence of the Linetype. The following example gets a linetype name from the user and employs AutoCAD to check for its existence: Public Sub CheckForLinetypeByException() Dim strLinetypeName As String Dim objLinetype As AcadLineType strLinetypeName = InputBox("Enter a Linetype name to search for: ") If "" = strLinetypeName Then Exit Sub ' exit if no name entered

On Error Resume Next ' handle exceptions inline Set objLinetype = ThisDrawing.Linetypes(strLinetypeName) If objLinetype Is Nothing Then ' check if obj has been set MsgBox "Linetype '" & strLinetypeName & "' does not exist" Else MsgBox "Linetype '" & objLinetype.Name & "' exists" End If End Sub

Linetype definitions are stored in linetype library files, which are external to drawing files and have the extension .lin. Linetypes are loaded by name from library files into similarly named Linetype objects in the drawing. Once loaded into a drawing, a Linetype object has no more connection to the library file. I don t cover the creation and definition of linetypes here, because no methods exist for customizing linetypes programmatically, but you can take a look at the AutoCAD Customization Guide in the online help files for details on creating custom linetypes. It s interesting to note that you can create custom linetypes by writing a linetype definition file programmatically and then loading it. You can load a Linetype object into your drawing using the Load method shown in the following code and detailed in Table 6-3. Set LinetypeObject = LinetypesCollection.Load(LinetypeName, _ LinetypeFilename) Table 6-3. Linetype Load Parameter Specifications

The AutoCAD default Linetype object definition file for standard linetypes is acad.lin. You can view the contents of this via the Linetype dialog box (click Format Linetype to bring it up) by clicking Load and browsing to the file (see Figure 6-3). You can also open a linetype definition file in any ASCII text editor such as Windows Notepad.