• What is automatic error handling?
• Configuring the automatic error handling.

	Estimated time: 10 mn

Operating mode

• the function returns an error value (e.g., fOpen returns "-1" if the specified file could not be opened).
• WLanguage detects the error (the ErrorOccurred variable is set to True) and the details of the error can be retrieved with ErrorInfo.

Implementation

• in the code editor: click the link "If error: By program" in the code editor:
  
• programmatically with the ErrorChangeParameter function.

Types of errors

• "non-fatal" errors (also called runtime errors): in most cases, these errors are handled in the code and do not stop the application. For example, opening a file that cannot be accessed or an archive that does not exist.
• "fatal" errors (also called programming errors): in most cases, these errors are linked to a development problem (access to a non-declared file, use of non-existing controls, etc.). A "fatal" error can also occur after a "non-fatal" error that was not processed properly. In this case, the application will be stopped.

• To understand the different error cases and how they are managed, we will use an example provided with WEBDEV.
  1. Go to the WEBDEV home page (Ctrl + <).
  2. On the home page, click "Open an example". The list of complete examples and training examples provided with WEBDEV is displayed.
  3. Type "Error" in the search area. Only the examples containing this word are listed.
     
  4. Select the "WW_Auto_Error_Management" project. The project is loaded.

• This project presents:
  • how to handle a non-fatal error (opening a non-existent archive).
  • how to handle a fatal error (dividing an integer by 0).
  • how to handle an error on multiple levels.

• Test the project (click in the quick access buttons).
  1. Click "Fatal error".
  2. The following page is displayed. This page is used the test the error when an integer is divided by 0.
     
  3. Click "Test error handling".
  4. When running the line of code that triggers the error, a procedure is automatically called. This procedure displays the error message and stops the current process.
  5. Click "OK".

• Click "Non-fatal error".
  1. The following page is displayed.
     
  2. Click "Test error handling".
  3. When running the line of code that triggers the error, an error message is displayed.
  4. Validate the error message.

• Click "Error on multiple levels".
  1. The following page is displayed. This page is used to test an error on multiple levels (process calling a procedure that opens an archive that does not exist).
     
  2. Click "Test error handling".
  3. When running the line of code that triggers the error:
     • the procedure returns "False" to the calling process.
     • the calling process displays an error message and stops the process.
  4. Validate the error message.

• Close the browser to end the test.

	Example	WEBDEV also handles HFSQL errors automatically. For more details, see Assisted HFSQL error handling.