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javascriptnode.jsmeteorpromisewhen-js

How do I use DDPClient with promises?


I am trying to use when.js with ddpclient. The code I have written is at the bottom of the post. When I attempt to use this, I get the following error below. Any ideas on how to get around this error? I am aware of another DDPclient that uses promises, but I am not keen to add an additional promise library.

Potentially unhandled rejection TypeError: Object #<Object> has no method '_nextId'
    at DDPClient.call (/Source/proj/node_modules/ddp/lib/ddp-client.js:329:17)
    at /Source/tellme/updater/node_modules/when/node.js:89:7
    at tryCatchReject (/Source/proj/node_modules/when/lib/makePromise.js:790:14)
    at FulfilledHandler.when (/Source/tellme/updater/node_modules/when/lib/makePromise.js:621:9)
    at ContinuationTask.run (/Source/tellme/updater/node_modules/when/lib/makePromise.js:741:24)
    at Scheduler._drain (/Source/proj/node_modules/when/lib/scheduler.js:56:14)
    at Scheduler.drain (/Source/proj/node_modules/when/lib/scheduler.js:21:9)
    at process._tickCallback (node.js:419:13)
    at Function.Module.runMain (module.js:499:11)
    at startup (node.js:119:16)

Code below:

"use strict";
var when           = require('when'),
    node           = require('when/node'),
    DDPClient      = require('ddp');


var ddpclient = new DDPClient({
    host: "localhost",
    port: 3000
});

var ddpconnect = node.lift(ddpclient.connect);
var ddpcall = node.lift(ddpclient.call);

//var ddpConnectPromise = node.lift(ddpclient.connect);

var obj = {"name": "john","age":25};

when(ddpconnect).then
(ddpcall("processObj", obj)).
    catch(function (error) {
        console.log(error);
    }).
    done();

EDIT: The following appears to get me closer, but I encounter a [TypeError: Object processObj has no method 'addListener'] error.

"use strict";
var when           = require('when'),
    node           = require('when/node'),
    DDPClient      = require('ddp');

var ddpConnectPromise = node.liftAll(DDPClient);

var ddpclient = new ddpConnectPromise({
    host: "localhost",
    port: 3000
});

var obj = {"name": "john","age":25};
when(ddpclient.connect).then(function (ddpclient) {
    ddpclient.call("processObj", sampleJSON);
}).
    catch(function (error) {
        console.log(error);
    }).
    done();

Solution

  • If you don't mind using bluebird, it has a promisifyAll you could use:

    var Promise = require("bluebird");
    Promise.promisifyAll(require("ddp").prototype);
    var DDPClient = require("ddp");    
    
    var ddpclient = new DDPClient({
      host: "localhost",
      port: 3000,
      /* optional: */
      auto_reconnect: true,
      auto_reconnect_timer: 500,
      use_ejson: true,           // Use Meteor's EJSON to preserve certain data types.
      use_ssl: false,
      maintain_collections: true // Set to false to maintain your own collections.
    });
    
    
    var obj = {"name": "john","age":25};
    
    ddpclient.connectAsync().then(function(ddpclient) {
        return ddpclient.callAsync("process", {}); // params is a required argument
    }).then(function(callResult) {
    
    }); // Logging errors is useless when using bluebird, so leave the .catch out