BridgeTalk message object

The message object defines the basic communication packet that is sent between applications. Its properties allow you to specify the receiving application (the target), the data to send to the target (the body), and the type of data that is sent. The messaging protocol is extensible; it allows you to define new types of data for the type property, and to send and receive arbitrary additional information with the headers property.


BridgeTalk message object constructor

Create a new message object using a simple constructor:

var bt = new BridgeTalk;

Before you send a message to another application, you must set the target property to the receiving application, and the body property to the data message (typically a script) you want to send.


BridgeTalk message object properties

body

Type: String

The data payload of the message.

  • If this is an unsolicited message to another application, typically contains a script packaged as a string. The target application’s full document object model (DOM) is available within the script.
  • If this message is a result returned from the static BridgeTalk onReceive method of a target application, directed to an onResult callback in this object, contains the return result from that method flattened into a string. See Passing values between applications.
  • If this message contains an error notification for the onError callback, contains the error message.

Read/write.


headers

Type: Object

A JavaScript object containing script-defined headers.

Use this property to define custom header data to send supplementary information between applications. You can add any number of new headers. The headers are name/value pairs, and can be accessed with the JavaScript dot notation (msgObj.headers.propName), or bracket notation (msgObj.headers[propName]). If the header name conforms to JavaScript symbol syntax, use the dot notation. If not, use the bracket notation.

The predefined header ["Error-Code"] is used to return error messages to a sender; see Messaging error codes.

Examples of setting headers:

bt.headers.info = "Additional Information";
bt.headers ["Error-Code"] = 8;

Examples of getting header values:

var info = bt.headers.info;
var error = bt.headers ["Error-Code"];

Read/write.


sender

Type: String

The application specifier for the sending application (see Application specifiers).

Read/write.


target

Type: String

The application specifier for the target, or receiving, application (see Application specifiers).

Read/write.


timeout

Type: Number

The number of seconds before the message times out.

If a message has not been removed from the input queue for processing before this time elapses, the message is discarded. If the sender has defined an onTimeout() callback for the message, the target application sends a time-out message back to the sender.

Read/write.


type

Type: String

The message type, which indicates what type of data the body contains. Default is ExtendScript.

You can define a type for script-defined data. If you do so, the target application must have a static BridgeTalk onReceive_ method that checks for and processes that type.

Read/write.


BridgeTalk message object callbacks

Note

The message callbacks are optional, and are not implemented by all message-enabled applications.

onError()

bridgeTalkObj.onError ()

A callback function that the target application invokes to return an error response to the sender. It can send JavaScript run-time errors or exceptions, or C++ exceptions.

To define error-response behavior, set this to a function definition in the following form:

bridgeTalkObj.onError = function( errorMsgObject ) {
  // error handler defined here
};

The body property of the received message object contains the error message, and the headers property contains the error code in its Error-Code property. See Messaging error codes.

The function returns undefined.


onReceived()

bridgeTalkObj.onReceived ()

A callback function that the target application invokes to confirm that the message was received. (Note that this is different from the static onReceive_ method of the BridgeTalk class that handles unsolicited messages.)

To define a response to receipt notification, set this to a function definition in the following form:

bridgeTalkObj.onReceived = function( origMsgObject ) {
  // handler defined here
};

The target passes back the original message object, with the body property set to the empty string.

The function returns undefined.


onResult()

bridgeTalkObj.onResult ()

A callback function that the target application invokes to return a response to the sender. This can be an intermediate response or the final result of processing the message.

To handle the response, set this to a function definition in the following form:

bridgeTalkObj.onResult = function( responseMsgObject ) {
  // handler defined here
};

The target passes a new message object, with the body property set to the result string. This is the result of the target application’s static BridgeTalk onReceive method, packaged as a UTF-8-encoded string. See Passing values between applications.


onTimeout()

bridgeTalkObj.onTimeout ()

A callback function that the target application invokes with a time-out message if time-out occurred before the target finished processing another message previously sent by this application.

To enable this callback, the message must specify a value for the timeout property.

To define a response to the timeout event, set this to a function definition in the following form:

bridgeTalkObj.onTimeout = function( timeoutMsgObject ) {
  // handler defined here
};

BridgeTalk message object functions

send()

bridgeTalkObj.send ([timoutInSecs[, launchParameters]])

timoutInSecs

Optional. A maximum number of seconds to wait for a result before returning from this function. The message is sent synchronously, and the function does not return until the target has processed the message or this number of seconds have passed.

If not supplied or 0, the message is sent asynchronously, and the function returns immediately without waiting for a result.

launchParameters

Optional. A string of parameters to append to the name of the target application when launching it, if the application is not already running.

If the target application is already running, this value is ignored.

Sends this message to the target application.

If the target application is not running and the message contains a body, the messaging system automatically launches the target application, passing in any supplied launch parameters. In this case, the message is queued rather than sent immediately, and this method returns false. The message is processed once the application is running.

Sending the message does not guarantee that the target actually receives it. You can request notification of receipt by defining an onReceived callback for this message object. (Note that this is different from the static onReceive method of the BridgeTalk class that handles unsolicited messages.)

Returns true if the message could be sent immediately, false if it could not be sent or was queued for sending later.


sendResult()

bridgeTalkObj.sendResult (result)

result You can send data of any type as the result value. The messaging framework creates a BridgeTalk message object, and flattens this value into a string which it stores in the body of that message. See Passing values between applications.

When processing an unsolicited message, the static BridgeTalk onReceive method can return an intermediate result to the sender by calling this method in the received message object. It invokes the onResult callback of the original message, passing a new message object containing the specified result value.

This allows you to send multiple responses to messages.

Returns true if the received message has an onResult callback defined and the response message can be sent, false otherwise.