Excel Macros Error Handling
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three flavors: compiler errors such as undeclared variables that prevent your code from compiling; user data entry error such as a user vba error handling best practices entering a negative value where only a positive number is acceptable; and
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run time errors, that occur when VBA cannot correctly execute a program statement. We will concern ourselves here excel vba on error exit sub only with run time errors. Typical run time errors include attempting to access a non-existent worksheet or workbook, or attempting to divide by zero. The example code in this
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article will use the division by zero error (Error 11) when we want to deliberately raise an error. Your application should make as many checks as possible during initialization to ensure that run time errors do not occur later. In Excel, this includes ensuring that required workbooks and worksheets are present and that required names are defined. The on error goto line more checking you do before the real work of your application begins, the more stable your application will be. It is far better to detect potential error situations when your application starts up before data is change than to wait until later to encounter an error situation. If you have no error handling code and a run time error occurs, VBA will display its standard run time error dialog box. While this may be acceptable, even desirable, in a development environment, it is not acceptable to the end user in a production environment. The goal of well designed error handling code is to anticipate potential errors, and correct them at run time or to terminate code execution in a controlled, graceful method. Your goal should be to prevent unhandled errors from arising. A note on terminology: Throughout this article, the term procedure should be taken to mean a Sub, Function, or Property procedure, and the term exit statement should be taken to mean Exit Sub, Exit Function, or Exit Property. The term end state
execution at a specified line upon hitting an error. Situation: Both programs calculate the square root of numbers. Square Root 1 Add the following code lines to the 'Square Root 1' command button. 1. First, we declare two Range objects. We call the Range objects
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rng and cell. Dim rng As Range, cell As Range 2. We initialize the Range object rng
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with the selected range. Set rng = Selection 3. We want to calculate the square root of each cell in a randomly selected range (this range vba on error msgbox can be of any size). In Excel VBA, you can use the For Each Next loop for this. Add the following code lines: For Each cell In rng Next cell Note: rng and cell are randomly chosen here, you can use any http://www.cpearson.com/excel/errorhandling.htm names. Remember to refer to these names in the rest of your code. 4. Add the following code line to the loop. On Error Resume Next 5. Next, we calculate the square root of a value. In Excel VBA, we can use the Sqr function for this. Add the following code line to the loop. cell.Value = Sqr(cell.Value) 6. Exit the Visual Basic Editor and test the program. Result: Conclusion: Excel VBA has ignored cells containing invalid values such as negative numbers and text. http://www.excel-easy.com/vba/examples/error-handling.html Without using the 'On Error Resume Next' statement you would get two errors. Be careful to only use the 'On Error Resume Next' statement when you are sure ignoring errors is OK. Square Root 2 Add the following code lines to the 'Square Root 2' command button. 1. The same program as Square Root 1 but replace 'On Error Resume Next' with: On Error GoTo InvalidValue: Note: InvalidValue is randomly chosen here, you can use any name. Remember to refer to this name in the rest of your code. 2. Outside the For Each Next loop, first add the following code line: Exit Sub Without this line, the rest of the code (error code) will be executed, even if there is no error! 3. Excel VBA continues execution at the line starting with 'InvalidValue:' upon hitting an error (don't forget the colon). Add the following code line: InvalidValue: 4. We keep our error code simple for now. We display a MsgBox with some text and the address of the cell where the error occurred. MsgBox "can't calculate square root at cell " & cell.Address 5. Add the following line to instruct Excel VBA to resume execution after executing the error code. Resume Next 6. Exit the Visual Basic Editor and test the program. Result: Do you like this free website? Please share this page on Google+ 3/6 Completed! Learn more about macro errors >Go to Top: Error Handling|Go to Next Chapter: String Manipulation Chapter<> Macro Errors Learn more, it's easy Debugging Error
Tools VBA Time Saver Kit โ code snippets & VBA reference VBA Web Scraping Kit โ easy scraping for Excel VBA Compiler (to VB.NET) VBA Multithreading Tool Excel Scrape HTML Add-In Documentation Google Charts Tool Excel SQL Add-In Excel Optimizer How to install Excel AddIns? VBA Questions? Contact Search http://analystcave.com/vba-proper-vba-error-handling/ for: Home ยป Proper VBA error handling Excel, MS Office, Outlook, PowerPoint, Word Proper VBA error handling http://stackoverflow.com/questions/6028288/properly-handling-errors-in-vba-excel (3 votes, average: 4.67 out of 5) Loading... October 22, 2015 AnalystCave 5 Comments Writing VBA code is hard, but properly debugging code is even harder. Sounds like non-sense? Well I dare say developers spend more time debugging code than writing it. Looking for errors is what developers do most of the time! A critical part of debugging is proper error handling (VBA error handling in our case). on error Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. โ Brian W. Kernighan However, today I don't want to expand on debugging VBA. That I covered in this post. No - today let's learn how to properly handle errors The Mouse Trap Analogy What is error handling? Take this analogy: Say you have a mouse (an error) in the house which turns vba on error up every now and then in the least expected moment as slips from your hands (an uncaught exception if you prefer). Without knowing where the mouse is and when it (the exception/error) will appear (in which line of code) you would need to search entire house to catch it (run through the entire code in our case). Obviously a better approach is setting mouse traps in several critical places in the house (corridors etc.) and waiting for the mouse to fall into your trap. So what is our mouse trap when speaking about VBA error handling? The On Error do this statement! Using VBA On Error The VBA On Error statement - tells VBA what it should do from now on, within the vicinity of the current block of code (Function or Sub), when an error/exception is raised. It is like setting a mouse trap - with the difference that you can tell it to drop the mouse off the dumpster or put it in your hands to manage. Let's remind the full syntax of the On Error statement in VBA first: On Error { GoTo [ line | 0 ] | Resume Next } Directly from MSDN we learn the different VBA error handling options we have with the On Error statement: On Error Goto - or On Error GoTo [ lineLabel | 0 | -1 ] if preffered. The Goto instruction in VBA let's you do a jump to a specific VBA code line number to follow through with error handling or simply
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Properly Handling Errors in VBA (Excel) up vote 34 down vote favorite 19 I've been working with VBA for quite a while now, but I'm still not so sure about Error Handling. A good article is the one of CPearson.com However I'm still wondering if the way I used to do ErrorHandling was/is completely wrong: Block 1 On Error Goto ErrCatcher If UBound(.sortedDates) > 0 Then // Code Else ErrCatcher: // Code End If The if clause, because if it is true, it will be executed and if it fails the Goto will go into the Else-part, since the Ubound of an Array should never be zero or less, without an Error, this method worked quite well so far. If I understood it right it should be like this: Block 2 On Error Goto ErrCatcher If Ubound(.sortedDates) > 0 Then // Code End If Goto hereX ErrCatcher: //Code Resume / Resume Next / Resume hereX hereX: Or even like this: Block 3 On Error Goto ErrCatcher If Ubound(.sortedDates) > 0 Then // Code End If ErrCatcher: If Err.Number <> 0 then //Code End If The most common way I see is that one, that the Error "Catcher" is at the end of a sub and the Sub actually ends before with a "Exit Sub", but however isn't it a little confusing if the Sub is quite big if you jump vice versa to read through the code? Block 4 Source of the following Code: CPearson.com On Error Goto ErrHandler: N = 1 / 0 ' cause an error ' ' more code ' Exit Sub ErrHandler: ' error handling code' Resume Next End Sub Should it be like in Block 3 ? Thank you for reading my question Greetings skofgar excel vba share|improve this question edited Jun 28 '14 at 13:37 asked May 17 '11 at 8:38 skofgar 7042916 7 rather than risk throwing an error with If Ubound(.sortedDates)>0 use If IsArrayAllocated(.sortedDates) = TRUE –osknows May 17 '11 at 8:53 Wow! that was fast :-) - thank you, that makes the On Error Goto unnecessary here... –skofgar May 17 '11 at 8:56 Bu