3.3.5 Exception Handling

3.3.5 Exception Handling

• to signal the error using lua_error;
• ignore the error, just doing nothing or returning some kind of error value.

The run time errors can be divided into three types:

• errors inside API calls, like CreateObject;
• errors when using LuaCOM objects (COM method calls);
• errors inside COM objects implemented in Lua.

The third type of error is always translated into a COM exception returned to the server. To ease debugging, these errors are also logged (if the logging facility has been activated), as the server can silenty ignore these exceptions, specially in events.

If the LuaCOM library is compiled with VERBOSE
defined, then a lot of informative messages are logged and all errors are displayed within a dialog box. This helps debug errors inside events on the fly, as these errors are commonly ignored by the server. Notice that this options slows down LuaCOM and can generate very big log files.

The behaviour of LuaCOM for the other two types can be customized. There is a table called config inside the LuaCOM table. This table holds three fields related to error handling:

abort_on_API_error

if false, LuaCOM silently fails on errors inside API calls. This is NOT true for errors caused by supplying bad parameters: these always generate calls to lua_error. The default value for this field is false.

abort_on_error

if false, errors inside method calls and property accesses are also ignored, possibly return nil where a return value is expected. The default value for this field is true.

last_error

every time a run time error occurr LuaCOM sets this field with the text describing the error. This field can be used to check if some operation failed; just remember to set it to nil before the operation of interest.

• • 3.3.5.0.1 Sample