VBScript Code Conventions

This guide provides an overview of VBScript coding conventions.

Overview

Coding conventions are suggestions designed to help you write VBScript and RhinoScript code. Coding conventions can include the following:

  • Naming conventions for objects, variables, and procedures
  • Commenting conventions
  • Text formatting and indenting guidelines

The main reason for using a consistent set of coding conventions is to standardize the structure and coding style of a script or set of scripts so that you and others can easily read and understand the code. Using good coding conventions results in clear, precise, and readable source code that is consistent with other language conventions and is intuitive.

Constant Naming

Earlier versions of VBScript had no mechanism for creating user-defined constants. Constants, if used, were implemented as variables and distinguished from other variables using all uppercase characters. Multiple words were separated using the underscore _ character. For example:

USER_LIST_MAX
NEW_LINE

While this is still an acceptable way to identify your constants, you may want to use an alternative naming scheme now that you can create true constants using the Const statement. This convention uses a mixed-case format in which constant names have a “con” prefix. For example:

conYourOwnConstant

Variable Naming

To enhance readability and consistency, use the following prefixes with descriptive names for variables in your VBScript code:

Subtype       Prefix       Example
Array       arr       arrLayers
Boolean       bln       blnFound
Byte       byt       bytRasterData
Date (Time)       dtm       dtmStart
Double       dbl       dblTolerance
Error       err       errOrderNum
Integer       int       intQuantity
Long       lng       lngDistance
Object       obj       objCurrent
Single       sng       sngAverage
String       str       strFirstName
                 

Variable Scope

Variables should always be defined with the smallest scope possible. VBScript variables can have the following scope:

Scope       Where Variable Is Declared       Visibility
Procedure-level       Event, Function, or Sub procedure.       Visible in the procedure in which it is declared.
Script-level       Outside any procedure.       Visible in every procedure in the script.
                 

Variable Scope Prefixes

As script size grows, so does the value of being able to quickly differentiate the scope of variables. A one-letter scope prefix preceding the type prefix provides this, without unduly increasing the size of variable names.

Scope       Prefix       Example
Procedure-level       None       dblVelocity
Script-level       s       sblnCalcInProgress
                 

Descriptive Names

The body of a variable or procedure name should use mixed case and should be as descriptive as necessary. Also, procedure names should begin with a verb, such as InitNameArray or ValidateLayer.

For frequently used or long terms, standard abbreviations are recommended to help keep name length reasonable. In general, variable names greater than 32 characters can be difficult to read. When using abbreviations, make sure they are consistent throughout the entire script. For example, randomly switching between Cnt and Count within a script or set of scripts may lead to confusion.

Code Commenting

All procedures should begin with a brief comment describing what they do. This description should not describe the implementation details (how it does it) because these often change over time, resulting in unnecessary comment maintenance work, or worse, erroneous comments. The code itself and any necessary inline comments describe the implementation.

Arguments passed to a procedure should be described when their purpose is not obvious and when the procedure expects the arguments to be in a specific range. Return values for functions and variables that are changed by a procedure, especially through reference arguments, should also be described at the beginning of each procedure.

Procedure header comments should include the following section headings:

Heading       Comment Contents
Purpose       What the procedure does (not how).
Assumptions       List of any external variable, control, or other element whose state affects this procedure.
Effects       List of the procedure’s effect on each external variable, control, or other element.
Inputs       Explanation of each argument that is not obvious. Each argument should be on a separate line with inline comments.
Return Values       Explanation of the value returned.
         

Remember the following points:

  • Every important variable declaration should include an inline comment describing the use of the variable being declared.
  • Variables, controls, and procedures should be named clearly to ensure that inline comments are only needed for complex implementation details.
  • At the beginning of your script, you should include an overview that describes the script, enumerating objects, procedures, algorithms, dialog boxes, and other system dependencies. Sometimes a piece of pseudocode describing the algorithm can be helpful.

Code Formatting

Screen space should be conserved as much as possible, while still allowing code formatting to reflect logic structure and nesting. Here are a few suggestions:

  • Indent standard nested blocks two spaces.
  • Indent the overview comments of a procedure one space.
  • Indent the highest level statements that follow the overview comments two spaces, with each nested block indented an additional two spaces.

In Sum

The following code adheres to VBScript coding conventions:

'****************************************************
' Purpose: Locates the first occurrence of a specified
'          layer in the LayerList array.
' Inputs:  arrLayerList: the list of layers to be searched.
'          strTargetLayer: the name of the layer to search for.
' Returns: The index of the first occurrence of the
'          strTargetLayer in the strLayerList array.
'          If the target layer is not found, return -1.
'****************************************************

Option Explicit

Function FindLayer(arrLayerList, strTargetLayer)
  Dim i          ' Loop counter.
  Dim blnFound   ' Target found flag
  FindLayer = -1 ' Default return value
  i = 0          ' Initialize loop counter
  Do While i <= UBound(arrLayerList) And Not blnFound
    If arrLayerList(i) = strTargetLayer Then
      blnFound = True ' Set flag to True
      FindLayer = i   ' Set return value to loop count
    End If
    i = i + 1         ' Increment loop counter
  Loop
End Function