SQCloudSetPubSubCallback

void SQCloudSetPubSubCallback (SQCloudConnection *connection, SQCloudPubSubCB callback, void *data);

Description

By using SQCloudSetPubSubCallback, you can set a callback function that will be automatically triggered each time a notification is received. It’s possible to call this function multiple times, but it will be executed only once. If you don’t set a callback function, your C code won’t be able to read any notifications sent by the Pub/Sub subsystem. The callback function is executed in an independent secondary thread, which allows the main thread to perform other commands without interruption.

Parameters

• connection: a valid connection object obtained by SQCloudConnect or SQCloudConnectWithString
• callback: the C callback to be called in each notification
• data: custom data to be transparently passed to the callback

Callback

void pubsub_callback (SQCloudConnection *connection, SQCloudResult *result, void *data);

Return value

Nothing.

Example

static my_callback(SQCloudConnection *connection, SQCloudResult *result, void *data) {
    // dump JSON notification
    // more about the JSON format: https://docs.sqlitecloud.io/docs/introduction/pubsub_payload
    SQCloudResultDump(connection, result);
}

int main (int argc, const char * argv[]) {
    // setup config
    SQCloudConfig config = {0};
    config.username = "myusername";
    config.password = "mypassword"

    SQCloudConnection *conn = SQCloudConnect("myproject.sqlite.cloud", SQCLOUD_DEFAULT_PORT, &config);
    if (SQCloudIsError(conn)) {
        printf("ERROR connecting: %s (%d)\n", SQCloudErrorMsg(conn), SQCloudErrorCode(conn));
        return -1;
    } else {
        printf("Connection to host OK...\n\n");
    }

    // set pub/sub callback
    SQCloudSetPubSubCallback(conn, my_callback, NULL);

    // start listening to a CHANNEL
    SQCloudExec(conn, "LISTEN channel1;");

    // ...
}