Pitfalls

These are some hints how to avoid common problems in your applications.

Disconnect handlers
Objects cannot be freed when there are still signal handlers connected. On widgets, you can call the method destroy(), which disconnects all handlers, destroys child widgets and removes itself from parents. For non-widgets, you can remember the handler_ids returned from the connect call like this:
handler_id = obj:connect('signal-name', signal_handler) obj:disconnect(handler_id)
Retrieving values from pointer arguments
Functions sometimes expect a pointer to a memory location where they can place a return value. If you specify nil for that argument, a NULL pointer is given to the function, which normally means that the return value should not be stored, rather discarded.
For int* and similar types, you should simply give a value to initialize the memory location with; the function can then overwrite it and it will be returned to the caller.
For double pointer to enum arguments you should specify gnome.NIL instead of nil, like in the following example:
-- call gchar* g_file_read_link(const gchar*, GError**) s, err = glib.file_read_link(path, gnome.NIL) if err then error(err.message) end
Wrong data type for vararg
When converting Lua values to call a library function with variable arguments, sometimes the wrong data type is used. For example, consider this:
glib.printf("%f\\n", 20)
In this case. an integer is given to printf, which actually expects a double. To avoid this, use a Boxed Value with a type cast, like this:
glib.printf("%f\\n", gnome.box(20, "double"))