lcOldError = ON("ERROR") ON ERROR * lcImage = LOCFILE("", "Images:GIF,BMP", "&Locate image:") ON ERROR &lcOldError. ENDTRY IF lCancel RETURN .t. Try / Catch would allow wrapping error prone areas and handle without completely exiting the app - like the Word instantiation above - that can fail for reasons outside the app, The following code associated with the Error event of each of the command buttons passes the error information to the single error-handling routine of the class: Copy LPARAMETERS nError, cMethod, nLine
Therefore, this is a shortcut that is functionally identical to the version shown in the previous example (except that the exception elevated to the outer handler will not be a user However, those functions are not really adequate to make this bullet-proof, since nested errors make things a bit complicated. Handling Run-Time Errors Visual Studio .NET 2003 Run-time errors occur after the application starts to execute. The following code anticipates this by making sure that the file exists before the user tries to use it: Copy cNewTable = GETFILE('DBF') IF FILE(cNewTable) USE (cNewTable) IN 0 ENDIF Your try this
The FINALLY block usually cleans up any resources allocated by the TRY block and is always the last code to run before control leaves the TRY...CATCH…FINALLY structure. Returning from Error Handling Code After the error handling code executes, the line of code following the one that caused the error is executed. Hmmm, thats what I assumed anyways. Catching an Exception When an error occurs in the TRY block, Visual FoxPro generates an exception, and the program moves to the first CATCH statement.
However, this type of error handler is generally not used in an object-oriented environment. cMsg="Error:" + ALLTRIM(STR(nError)) + CHR(13) ; + MESSAGE()+CHR(13)+"Program:"+PROGRAM() nAnswer = MESSAGEBOX(cMsg, 2+48+512, "Error") DO CASE CASE nAnswer = 3 &&Abort CANCEL CASE nAnswer = 4 &&Retry RETRY OTHERWISE && Ignore RETURN The program examines CATCH statements in the order that they appear in the CATCH block to see if one of them can handle the exception. Copy Parameters nError, cMethod, nLine DO CASE CASE nError = 13 && Alias not found cNewTable = GETFILE('DBF') IF FILE(cNewTable) SELECT 0 USE (cNewTable) This.SkipTable = ALIAS() ELSE This.SkipTable = ""
For this reason, Visual FoxPro 3.0 (the first "Visual" version of FoxPro and also the first version that supported object-oriented development) introduced an Error() event. In this case, the error handler is the code contained in VFP. In total, however, the object might require a very complex error handler.Another problem is that this type of error handler makes it very difficult to "exit gracefully" whenever an error has https://msdn.microsoft.com/en-us/library/cb8f2ysx(v=vs.80).aspx For example, if you call a data environment's CloseTables method in code when AutoCloseTables is set to true (.T.) and then release the form, an internal error is generated when Visual
You're right, that's more or less what I have now. If you want the container object's Error event to handle errors for its member objects, you can pass error information from the member object's Error event to container's Error event by The solution is not influenced by outside error handling. The original (system) exception object will end up as the UserValue.
The ENDTRY statement ends the TRY...CATCH…FINALLY structure. This Site Debugging can be very uncomfortable with TRY...CATCH (Problem with set next statement, no RETRY, no stackinfo, sometimes incomplete info where the error occured ...). The beauty of classes is that you can encapsulate everything a control needs, including error handling, so that you can use the control in a variety of environments. Once that object is instantiated, the CreditCard class raises an error (exception) using the THROW command and the new exception object as the expression.
ON ERROR lError = .T. * We run the regular code LOCAL oWord as Word.Application oWord = CREATEOBJECT("Word.Application") oWord.Application.Visible = .T. This way you see more related code that is error-prone (instancing Word, then loading a document), that is wrappeed inside an error handler. -- Alex Feldstein Also, Try...Catch has nesting capabilities Markus’ client list contains some of the world's largest companies, including many on the Fortune 500. Why should one not use ON ERROR?
Another option would be to issue a RETRY, which would run the line that failed again, causing another error, which would result in an endless loop if the handler just tried Here is a gotcha: If you have anything (even a comment) in an error event, that will override the ON ERROR error handler. To do so, the developer simply instantiates this object and passes some text to the Export() method. In other words, if each form has its own private data session, you need to SET TALK separately in each form (usually in the Load event).In addition, you can set the
If you want all objects based on a particular class to use the same error-handling behavior, add Error event code to the class definition, for example, for a custom class or For a complete list of Visual FoxPro error messages and error numbers, see Help. The parameter passed to this method represents an invalid credit card (error handling is easier to demonstrate if things fail).
Because a Java-programmer could say "oh, this is so unOOP, it's so unfashioned"? Here is an example:DEFINE CLASS WordExport AS Custom FUNCTION Export(lcText1,lcText2) LOCAL lReturnValue lReturnValue = .T. What is specified by ON ERROR Does anyone have any examples or sample code? However, I would like the method to return .F.
Markus has been published extensively including MSDN Magazine, Visual Studio Magazine, his own CODE Magazine, and much more. The FINALLY statements always run before handling these commands except when CANCEL or QUIT is used. That is, you can insert a TRY...CATCH…FINALLY structure within a TRY, CATCH, or FINALLY block. If you wish to bypass the FINALLY statement, you need to provide code at the beginning of the FINALLY block that checks for a condition and breaks out of the block
ENDIF ENDIF With: TRY use xyz * this way, the same CATCH will handle errors * on instancing Word, or on attempting to open * a Word document oWord = CreateObject("word.application") I'd recommend capturing everything except for the current stack level (since that would always be the error handling procedure. These errors could occur when the user chooses any one of the buttons; therefore, it doesn't make sense to have four separate error handling methods. OTHERWISE * display a generic message, maybe * send high priority mail to an administrator ENDPROC Handling Errors in Classes and Objects When an error occurs in method code, Visual FoxPro
Even the following, more obviously nested command works: on error on error return && Don't return on the first error, but do on the second one. TRY oWord.Documents.Add("MyTemplate.dot") CATCH oWord.Documents.Add() ENDTRY oWord.Selection.InsertAfter(lcText1) oWord.Selection.InsertAfter(lcText2) CATCH lReturnValue = .F. If code for an Error event exists to handle the error, then the Error event takes precedence. So while a new application could use TRY...CATCH exclusively (perhaps there would still be a use for Error()), but you have to go through and make sure it won't break anything
Note however, that the error may have occurred before Word ever got instantiated. If the user doesn't want to exit the current application, the routine can return control to the application. The method then opens an instance of Word, makes it visible, creates a new document and exports the text.What would happen if the user actually closed Word right after a new The problem with that is that the error method takes precedence over the ON ERROR handler, hence rendering the ON ERROR useless.Introducing: Try/CatchTo solve these issues, Visual FoxPro 8.0 introduces "Structured
oWord.Documents.Add() oWord.Selection.InsertAfter(lcText1) oWord.Selection.InsertAfter(lcText2) CATCH lReturnValue = .F. Developing Visual FoxPro Applications Testing and Debugging Applications Handling Run-Time Errors Handling Run-Time Errors Class and Object Error Handling Class and Object Error Handling Class and Object Error Handling Procedural Error