Error Handling
Compared to traditional / classic 4GL languages (like Informix® 4GL), Querix 4GL allows the developer to have much greater control over event handling with the extended behaviour of the WHENEVER ERROR statement.:
WHENEVER [ ANY | GLOBAL | MODULE ] <event_type> <event_action>
Where <event_type> can be any one of:
- ARGUMENT ERROR
- RETURN ERROR
- UNDEFINED FUNCTION
- INTERRUPT
- QUIT
- TERMINATE
- HANGUP
- FATAL ERROR
- <identifier>
And the <event action> can be any one of:
- CONTINUE
- STOP
- CALL <function_name>
This model provides a slight fundamental difference to the Informix 4GL WHENEVER ERROR statment. Under Informix 4GL, the approximate scope of a WHENEVER
statement is MODULE, whereby Querix allows to specify the scope global or module.
detail at a later stage.
Two new forms of WHENEVER have been added to handle , 'Global event handling' &
'event handling for a module or library'. You can now use:
WHENEVER GLOBAL ERROR call my_global_handler
WHENEVER MODULE ERROR call my_module_handler
These two forms handlers to be set which are called when no handler is defined
locally, allowing a default error handling function to be specified at a single
point.
The WHENEVER MODULE form is similar to WHENEVER GLOBAL, but causes the specified
error handling behaviour to only be executed when the program is executing a
function in the current module or library.
The WHENEVER GLOBAL and WHENEVER MODULE statements must be executed and can go
into the program or module initilization functions.
