Futurebasic/Language/Reference/on error fn
ON ERROR FN / GOSUB
[edit | edit source]Statements
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Syntax
[edit | edit source]<code><b>ON ERROR</b> {<b>FN</b> userFunction|<b>GOSUB</b>{<i>lineNumber</i>|<i>"stmtLabel"</i>}}</code>
Revised
[edit | edit source]June, 2001 (Release 5)
Description
[edit | edit source]This statement designates and enables the routine that FB will call when certain kinds of errors occur. There may only be one ON ERROR
vector. If you use a second call to ON ERROR FN
, the new routine replaces the old version in subsequent calls. However you can deactivate or reactivate error trapping as often as you need. Using the ON ERROR END
/ON ERROR RETURN
statements you can switch between the default behavior and your error handler.
Example:
<code><b>LOCAL FN</b> handleFileError<br> <b>ÊÊPRINT</b> "Sorry. Something has gone wrong."<br> <b>ÊÊSTOP</b><br> <b>END FN</b></code> <code><b>ON ERROR FN</b> handleFileError<br> <b>OPEN</b> "I",#1,"this file does not exist"</code>
Note:
If you use the ON ERROR FN userFunction
syntax, then userFunction
must refer to a function which was defined or prototyped at an earlier location in the source code. Your error handling function should not take any parameters, nor return a result.