Working with Domains

_about.md

Working with domains

app.js

// In this example we'd like to have a factory that works per request and allows to keep track of created Models
// We create a factory per request and create a domain to which we attach the factory
// That way the singleton is automatically shared with all parts of the application under `process.domain.*`

// app.js
var express = require('express'),
    domain = require('domain'),
    createFactory = require('./factory'),
    Layout = require('./layout'),
    app = express();

app.all('*', function(req, res, next) {
    // We create a factory for every request and attach it to a new domain
    // That way it is automatically available in all code executed in the context of this request
    
    var requestDomain = domain.create();
    var perRequestFactory = createFactory();

    requestDomain.factory = perRequestFactory; // put this onto the domain, so inside run, the factory is available

    requestDomain.run(function () {
        var view = new Layout();

        var responseTime = Math.random() * 2500; // random response time
        // Simulate async tasks
        setTimeout(function () {
            res.send(perRequestFactory.serializeModels());
        }, responseTime);
    });

});

app.listen(8000);

factory.js

// A factory for factories
// For every request we create a new one

var Model = require('backbone').Model;

module.exports = function createFactory () {
    var allModels = [];

    return {
        createModel: function (data) {
            var model = new Model(data);
            allModels.push(model);
            return model;
        },
        serializeModels: function () {
            return allModels.map(function (model) {
                return model.toJSON();
            });
        },
        reset: function () {
            allModels = [];
        }
    }
};

layout.js

var Backbone = require('backbone');
var SubView = require('./subview');


Backbone.$ = require('cheerio');


module.exports = Backbone.View.extend({
    initialize: function () {
        this.subView = new SubView();
        this.$el.append(this.subView.$el);
    },
    render: function(){
        this.subView.render();
        this.$el.append(this.subView.$el);
    }
});

subview.js

var View = require('backbone').View;

module.exports = View.extend({
    initialize: function () {
        this.viewState = process.domain.factory.createModel({
            collapsed: true,
            hidden: false
        });
    },
    render: function(){
        
        this.$el.empty();
        this.$el.html(this.viewState.toJSON());
        
    }
});