OpenAjaxPublishSync

Purpose

.OpenAjaxPublishSync Client method publishes messages to the OpenAjax Hub in the Open Client browser. Subscribers to the message as defined in the $topic parameter receive the message payload as contained in the $data parameter. If the kernel tries to call the method when connected to an older Open Client, a rollback run-time error occurs and the current function terminates.

Note: When using the OpenAjaxPublishSync Client method, the kernel waits for a response from the method before continuing and a value is returned in the $return parameter.

Click here for more information about the OpenAjax Hub.

Object Type

Client

Syntax

variable=Client.OpenAjaxPublishSync ($topic, $data, $return)

Operation

variable is a numeric variable that captures the return code.

$topic defines a message in the OpenAjax Hub.

$data contains the message payload that is sent to subscribers of the $topic parameter in the hub. The maximum payload length is 2000 bytes.

$return accepts the return string from the Client.

Remarks

If using this feature, it is recommended that the TP_ROLLBACK setting is set to 'Y' in the pro4v[n].ini file.

Example

The following is an example that demonstrates OpenAjaxPublishSync:

$topic = “Weather�?

$data = "{'town': 'Luton', 'TempMin': '4C', 'TempMax':'11C', 'Outlook':'Rain & Wind', 'WindSpeedMax':'35mph', 'Tomorrow': 'Sunny'}"

Client.OpenAjaxPublishSync($topic, $data, $Result)

The html document below shows the contents of a Template page (the Template page defined in an Open Client Session Definition) that subscribe to and handle the published event from the logic example.

Example Template Page

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>

<head>

</head>

<body>

</div>

OpenAjax.hub.subscribe("Weather ", function(event, obj){ obj.returnValue = "Weather received.�? });

</script>

</body>

</html>

If you then publish the weather using 'sync' method the “Weather received.�? message is the $result parameter.

The OpenAjaxPublishSync method waits for a return value from the browser before continuing.

The data to be returned from the browser is set using the 'returnValue' property of the supplied published object.
In the Javascript example, this is referenced by the 'obj' parameter. This data is passed to the '$return' parameter of the Client.OpenAjaxPublishSync method call.
The 'publishData' supplied by the Client.OpenAjaxPublishSync method call is passed in as the 'publisherData' property of the 'obj' object.