ToC path:

UDA Event Handler

Database events can be managed by registering an event handler. The function mco_uda_register_event_handler() requires an argument of type mco_uda_event_handler as define below in mcouda.h:

 
    typedef MCO_RET (*mco_uda_event_handler)( mco_trans_h t, mco_uda_object_handle_p obj, const mco_dict_event_info_t *event_info, /* inout */ void *param );

Following is an example of an event handler implementation:

     
    MCO_RET sync_event_handler(mco_trans_h t, mco_uda_object_handle_p obj, const mco_dict_event_info_t *event_info, void *param)
    {
        mco_dict_struct_info_t struct_info;
        mco_dict_field_info_t field_info;
        mco_uda_value_t val;
        autoid_t obj_autoid;
         
        mco_dict_struct(metadict, 0, obj->struct_no, &struct_info);
        mco_dict_field_name(metadict, 0, obj->struct_no, "autoid", &field_info);
        val.type = MCO_DD_AUTOID;
        mco_uda_get(obj, field_info.field_no, 0, &val);
        obj_autoid = val.v.u8;
         
        if (event_info->type == MCO_EVENT_UPDATE || event_info->type == MCO_EVENT_CLASS_UPDATE) 
        {
            mco_dict_field(metadict, 0, obj->struct_no, event_info->field_no, &field_info);
            printf("Sync. event for obj %" INT8_FORMAT "d: class %s, event_no=%d, type=UPDATE, when=%s, field=%s, value=",
            obj_autoid, struct_info.name, event_info->event_no, ((int)param == MCO_AFTER_UPDATE) ? "AFTER" : "BEFORE", field_info.name);
             
            print_obj_field(obj, &field_info);
        } else {
            printf("Sync. event for obj %" INT8_FORMAT "d: class %s, event_no=%d, type=", obj_autoid, struct_info.name, event_info->event_no);
            switch (event_info->type) {
                case MCO_EVENT_NEW        : printf("NEW"); break;
                case MCO_EVENT_DELETE     : printf("DELETE"); break;
                case MCO_EVENT_DELETE_ALL : printf("DELETE_ALL"); break;
                case MCO_EVENT_CHECKPOINT : printf("CHECKPOINT"); break;
                default                   : printf("UNKNOWN"); dbg_exit(1);
            }
        }
        printf("\n");
        return MCO_S_OK;
    }