How can I use Socket.IO with promises?

问题:

As a part of an ongoing effort, I'm changing my current callbacks technique to promises using blue-bird promise library.

I would like to implement this technique with Socket.IO as well.

• How can I use Socket.IO with promises instead of callbacks?
• Is there any standard way of doing it with Socket.IO? any official solution?

回答1:

You might look into Q-Connection, which facilitates RPC using promises as proxies for remote objects and can use Socket.IO as a message transport.

回答2:

Bluebird (and many other promise libraries) provide helper methods to wrap your node style functions to return a promise.

var readFile = Promise.promisify(require("fs").readFile);

readFile("myfile.js", "utf8").then(function(contents){ ... });

https://github.com/petkaantonov/bluebird/blob/master/API.md#promisification

Returns a function that will wrap the given nodeFunction. Instead of taking a callback, the returned function will return a promise whose fate is decided by the callback behavior of the given node function. The node function should conform to node.js convention of accepting a callback as last argument and calling that callback with error as the first argument and success value on the second argument.

回答3:

have a look here https://www.npmjs.com/package/socket.io-rpc

var io = require('socket.io').listen(server);
var Promise = require('bluebird');
var rpc = require('socket.io-rpc');

var rpcMaster = rpc(io, {channelTemplates: true, expressApp: app})
        //channelTemplates true is default, though you can change it, I would recommend leaving it to true,
        //                   false is good only when your channels are dynamic so there is no point in caching
    .expose('myChannel', {
    //plain JS function
    getTime: function () {
        console.log('Client ID is: ' + this.id);
        return new Date();
    },
    //returns a promise, which when resolved will resolve promise on client-side with the result(with the middle step in JSON over socket.io)
    myAsyncTest: function (param) {
        var deffered = Promise.defer();
        setTimeout(function(){
            deffered.resolve("String generated asynchronously serverside with " + param);
        },1000);
        return deffered.promise;
    }
});


io.sockets.on('connection', function (socket) {
    rpcMaster.loadClientChannel(socket,'clientChannel').then(function (fns) {
        fns.fnOnClient("calling client ").then(function (ret) {
            console.log("client returned: " + ret);
        });
    });

});