As Senior Engineer Paul Lefebvre wrote back in 2022, Xojo added the ability to create Code Assistants starting with Xojo 2022r1. Code Assistants are functions that manipulate the code selected in the Code Editor to help with various code editing tasks. Code Assistants are written in XojoScript, but XojoScript has no access to the Xojo Debugger. Fortunately, there’s a simple solution to this problem.

Xojo’s Code Assistant Tester example project makes it easy to test and debug your code before you create your Code Assistant. Go to File > New Project, click on Examples then open the IDE folder to find it. With this example, you can enter the code that would go into your eventual XojoScript that will be your Code Assistant. Because this code is in methods in Xojo itself, you can test it and debug it with the Xojo Debugger.

Here’s a quick video on how to use Code Assistants and the Code Assistant Tester:

If you write some handy Code Assistants, consider sharing them on the Xojo Forum they could be useful to others in the community.

Geoff Perlman is the Founder and CEO of Xojo. When he’s not leading the Xojo team he can be found playing drums in Austin, Texas and spending time with his family.

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// This script takes the current selected comment
// and changes the comment prefix.

Function Name() As String
  Return "Swap Comment Prefix"
End Function

Function CanEdit(selection As String) As Boolean
  // Check if comments starts with // or '.
  Return Left(selection, 2) = "//" Or Left(selection, 1) = "'"
End Function

Function Edit(selection As String) As String
  // Swap // with ' or swap ' with //
  If Left(selection, 1) = "'" Then
    Return Replace(selection, "'", "//")
  ElseIf Left(selection, 2) = "//" Then
    Return Replace(selection, "//", "'")
  End If
End Function

This is not too lengthy, so let’s examine the parts. With a code assistant, there are three methods that are required: Name, CanEdit and Edit.

The Name() method returns a string containing the name that will appear in the Code Assistants menu. You can nest items using slashes, so “Paul/Swap Comments Prefix” would have this appear in Code Assistants->Paul->Swap Comments Prefix.

The CanEdit() method provides the code editor selection as a parameter. In this method you should return True if this code assistant is allowed to edit the selection. If you return True, the name will appear in the Code Assistants menu. If you return False it will not appear in the menu.

The code above checks if the selected text starts with the comment prefixes we want to swap: // or ‘.

The Edit() method is where you modify the selection, returning new text that will replace the selection in the Code Editor. This method does a single replace of “//“ with “’” and “’” with “//“.

Save the above script as SwapCommentPrefix.xojo_code_assistant and copy it to the Scripts folder in your IDE install folder.

If Xojo was running, you can tell it to reload those scripts by holding down Cmd (on Mac) or Control (Windows/Linux) when right-clicking.

Now type a comment like this:

‘ This is a comment.

Select that comment and right-click. Choose Code Assistants->Swap Comment Prefix.

The line now shows as:

// This is a comment.

For other sample Code Assistant scripts, go to Examples/Advanced/IDE Scripts/Code Assistants in the Xojo download folder.

Learn more in this video! Be sure to share your Code Assistant scripts in the forum!

First, you can find the example by opening the Project Chooser (File->New), clicking “Examples” and then going to Advanced, XojoScript and selecting Evaluator.

Looking at the project you’ll see it has a primary Window (MainWindow) and a class called Evaluator. The Evaluator class is a subclass of XojoScript.

The way this project works is that it takes the formula that was entered in the TextField of the window and embeds it into XojoScript source and then runs the source to get the result, which is returned back to the window to display.

Take a look at the Eval method on the Evaluator class. It’s primary code is this:

 Dim source As String
 
 source = "Dim expr As Variant = " + expression + EndOfLine + _
 "If expr.IsNumeric Then " + EndOfLine + _
 "mResult = Str(expr.DoubleValue)" + EndOfLine + _
 "Else " + EndOfLine + _
 "mResult = expr" +EndOfLine + _
 "End If"
 
 Self.Source = source
 Self.Context = Self // So we can refer to Evaulator.mResult property in XojoScript
 Self.Run
 
 Return mResult

This code assigns the XojoScript source using the Source property and sets the Context property to itself which allows the XojoScript source to access the mResult property on the Evaluator class. Then it runs the XojoScript source.

This source assigns the formula to the line “Dim expr As Variant”, checks if the result is numeric and if it is, converts it to a string. The expression is then assigned to the mResult property so that it can be accessed outside the XojoScript source.

Which, back in the code for Eval, is what gets returned to the caller to display.

Of course, this does require that you pass in a valid Xojo expression that can be evaluated. Some example include:

• Hex(255), which returns FF
• Left(“XojoScript, 4), which returns Xojo

If you pass something that cannot be evaluated, you’ll get an error message which is displayed by either the CompilerError or RuntimeError events on the Evaluator class. Take a look at the ErrorCodeToString method to see a list of the possible errors. For example, the values below all generate an error:

• 54 + “test” displays a “Type Mismatch” error.
• “Dim i As Integer” displays a “Syntax does not make sense” error.
• PMT(45) displays “Unidentified identifier”

This sort of technique can be useful for projects where you want to dynamically run calculations that are not determined until the app is run.

As you roll into the new year, it can be a good time to review your workflows to see if you can make some improvements. Perhaps IDE Scripts can help with that.

I was reminded of this by the wonderful “Share useful IDE scripts” forum conversation (started by Jeremy Cowgar) that has some great script examples. Be sure to check it out. Some of the script examples include:

• Sort lines of code
• Toggle Find Panel Display
• Reload a Project
• Find/Find Next
• Project Diff
• Markdown Preview
• Obfuscate Code

And don’t forget Jeremy’s wonderful Code Formatting IDE Script which is available on GitHub:

• Xojo Format Code

When you’re ready to create your own scripts, read the IDE Scripting docs in the Xojo Dev Center:

• IDE Scripting
• IDE Scripting Commands

I’ve written about IDE Scripts before (Build All The Things and IDE Scripts Included with Xojo), so also be sure to review those scripts for examples and ideas.