roslib/src/core/Service.js

The standard ROS Javascript Library

/**
 * @fileoverview
 * @author Brandon Alexander - baalexander@gmail.com
 */

var ServiceResponse = require('./ServiceResponse');
var ServiceRequest = require('./ServiceRequest');
var EventEmitter2 = require('eventemitter2').EventEmitter2;

/**
 * A ROS service client.
 *
 * @constructor
 * @params options - possible keys include:
 *   * ros - the ROSLIB.Ros connection handle
 *   * name - the service name, like /add_two_ints
 *   * serviceType - the service type, like 'rospy_tutorials/AddTwoInts'
 */
function Service(options) {
  options = options || {};
  this.ros = options.ros;
  this.name = options.name;
  this.serviceType = options.serviceType;
  this.isAdvertised = false;

  this._serviceCallback = null;
}
Service.prototype.__proto__ = EventEmitter2.prototype;
/**
 * Calls the service. Returns the service response in the
 * callback. Does nothing if this service is currently advertised.
 *
 * @param request - the ROSLIB.ServiceRequest to send
 * @param callback - function with params:
 *   * response - the response from the service request
 * @param failedCallback - the callback function when the service call failed (optional). Params:
 *   * error - the error message reported by ROS
 */
Service.prototype.callService = function(request, callback, failedCallback) {
  if (this.isAdvertised) {
    return;
  }

  var serviceCallId = 'call_service:' + this.name + ':' + (++this.ros.idCounter);

  if (callback || failedCallback) {
    this.ros.once(serviceCallId, function(message) {
      if (message.result !== undefined && message.result === false) {
        if (typeof failedCallback === 'function') {
          failedCallback(message.values);
        }
      } else if (typeof callback === 'function') {
        callback(new ServiceResponse(message.values));
      }
    });
  }

  var call = {
    op : 'call_service',
    id : serviceCallId,
    service : this.name,
    type: this.serviceType,
    args : request
  };
  this.ros.callOnConnection(call);
};

/**
 * Advertise the service. This turns the Service object from a client
 * into a server. The callback will be called with every request
 * that's made on this service.
 *
 * @param callback - This works similarly to the callback for a C++ service and should take the following params:
 *   * request - the service request
 *   * response - an empty dictionary. Take care not to overwrite this. Instead, only modify the values within.
 *   It should return true if the service has finished successfully,
 *   i.e. without any fatal errors.
 */
Service.prototype.advertise = function(callback) {
  if (this.isAdvertised || typeof callback !== 'function') {
    return;
  }

  this._serviceCallback = callback;
  this.ros.on(this.name, this._serviceResponse.bind(this));
  this.ros.callOnConnection({
    op: 'advertise_service',
    type: this.serviceType,
    service: this.name
  });
  this.isAdvertised = true;
};

Service.prototype.unadvertise = function() {
  if (!this.isAdvertised) {
    return;
  }
  this.ros.callOnConnection({
    op: 'unadvertise_service',
    service: this.name
  });
  this.isAdvertised = false;
};

Service.prototype._serviceResponse = function(rosbridgeRequest) {
  var response = {};
  var success = this._serviceCallback(rosbridgeRequest.args, response);

  var call = {
    op: 'service_response',
    service: this.name,
    values: new ServiceResponse(response),
    result: success
  };

  if (rosbridgeRequest.id) {
    call.id = rosbridgeRequest.id;
  }

  this.ros.callOnConnection(call);
};

module.exports = Service;