Error Trapping Vba Excel
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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 entering a negative value where on error goto errorhandler only a positive number is acceptable; and run time errors, that occur
On Error Goto Errhandler
when VBA cannot correctly execute a program statement. We will concern ourselves here only with run time errors. Typical on error goto function vba run time errors include attempting to access a non-existent worksheet or workbook, or attempting to divide by zero. The example code in this article will use the division by zero error on error goto label (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 more checking you do before the real work of your application begins, the
On Error Goto Sub
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 statement should be taken to mean End Sub , End Function, End Property, or just End. The On Error Statement The heart of error hand
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Excel Vba Msgbox
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 http://www.cpearson.com/excel/errorhandling.htm 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 http://stackoverflow.com/questions/6028288/properly-handling-errors-in-vba-excel 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
the wrong time. The application may crash. A calculation may produce unexpected results, etc. You can predict some of these effects and take appropriate actions. Some other problems are not under your control. Fortunately, both Microsoft Excel and http://www.functionx.com/vbaexcel/Lesson26.htm the VBA language provide various tools or means of dealing with errors. Practical Learning:Introducing Error Handling Open the Georgetown Dry Cleaning Services1 spreadsheet and click the Employees tab Click the Payroll tab Click the TimeSheet tab To save the workbook and prepare it for code, press F12 Specify the folder as (My) Documents In the Save As Type combo box, select Excel Macro-Enabled Workbook Click Save Introduction to Handling Errors To deal with errors in your code, on error the Visual Basic language provides various techniques. One way you can do this is to prepare your code for errors. When an error occurs, you would present a message to the user to make him/her aware of the issue (the error). To prepare a message, you create a section of code in the procedure where the error would occur. To start that section, you create a label. Here is an example: Private Sub cmdCalculate_Click() ThereWasBadCalculation: End Sub After on error goto (under) the label, you can specify your message. Most of the time, you formulate the message using a message box. Here is an example: Private Sub cmdCalculate_Click() ThereWasBadCalculation: MsgBox "There was a problem when performing the calculation" End Sub If you simply create a label and its message like this, its section would always execute: Private Sub cmdCalculate_Click() Dim HourlySalary As Double, WeeklyTime As Double Dim WeeklySalary As Double ' One of these two lines could produce an error, such as ' if the user types an invalid number HourlySalary = CDbl(txtHourlySalary) WeeklyTime = CDbl(txtWeeklyTime) ' If there was an error, the flow would jump to the label WeeklySalary = HourlySalary * WeeklyTime txtWeeklySalary = FormatNumber(WeeklySalary) ThereWasBadCalculation: MsgBox "There was a problem when performing the calculation" End Sub To avoid this, you should find a way to interrupt the flow of the program before the label section. One way you can do this is to add a line marked Exit Sub before the label. This would be done as follows: Private Sub cmdCalculate_Click() Dim HourlySalary As Double, WeeklyTime As Double Dim WeeklySalary As Double ' One of these two lines could produce an error, such as ' if the user types an invalid number HourlySalary = CDbl(txtHourlySalary) WeeklyTime = CDbl(txtWeeklyTime) ' If there was an error, the flow would jump to the label WeeklySalary = HourlySalary * WeeklyTime txtWeeklySalary = FormatNumber(WeeklySalary)