ToC path:

mco_register_eventname_handler()

This function registers a synchronous event handler for an add, delete or checkpoint event.

Prototype

    MCO_RET     mco_register_eventname_handler(    /*IN*/ mco_trans_h trans,
                             /*IN*/ mco_eventname_handler,
                             /*IN*/ void *param);

Arguments

trans

A transaction handle returned by mco_trans_start().

mco_eventname_handler

A pointer to the handler function.

param

A pointer to user-defined storage.

Description

This function registers a call-back function that the runtime will invoke whenever the event eventname occurs. Events are defined in the database schema by specifying the event type (new, delete, update or checkpoint) and the name of the handler function to be called. Multiple handlers for a given eventname can be registered. The void param can be used to pass any user-defined data structure between the application and the event handler.

Return Codes

MCO_S_OK

The handler was registered successfully.

MCO_E_ACCESS

Transaction is not MCO_READ_WRITE.

Example


    Schema snippet:

    declare database evdb;

    class MyClass
    {
        uint4 u4;

        event <new>     newEvent;
        list;
    };

    evdb.h snippet:

    /* class MyClass methods */
    MCO_RET      MyClass_new                          ( mco_trans_h t, /*OUT*/ MyClass *handle );
    ...
    typedef MCO_RET (*mco_newEvent_handler)( mco_trans_h t, MyClass * obj, MCO_EVENT_TYPE et, /*INOUT*/ void *param);

    MCO_RET      mco_register_newEvent_handler        ( mco_trans_h t, mco_newEvent_handler handler, void * param );

    MCO_RET      mco_unregister_newEvent_handler      ( mco_trans_h t, mco_newEvent_handler handler);

    Application snippet:

    MCO_RET new_handler(mco_trans_h t, MyClass* obj, MCO_EVENT_TYPE et,  /*INOUT */void* param)
    {
        autoid_t id;
        MyClass_autoid_get(obj, &id);
        printf("\tEvent \"Object New\" : object (%d) created\n", autoid2int(id));
        return MCO_S_OK;
    }

    int register_events(mco_db_h db)
    {
        MCO_RET rc;
        mco_trans_h t;

        mco_trans_start(db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t);
        rc = mco_register_newEvent_handler( t, &new_handler, (void*)0 );

        ...
    }