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World object in cucumber.js or where to put state in cucumber tests

I'm trying to save the current navigation state in one step (the page on a platform with multiple websites) in cucumber.js so the following steps of a scenario can deal with it. I thought using the World object for it, but mysterious things are happening.
I have a navigation state object like this:
module.exports = {
pageName:null,
siteName: null,
isLoggedIn: false
}
Then I have a NavigationStateManager like this
function NavigationStateManager() {
var state
this.setState = function(stateP) {
state = stateP
}
this.setPage = function(pageNameP, siteNameP, isLoggedInP) {
// among other things do something link this:
state.pageName = pageNameP
state.siteName = siteNameP
state.isLoggedIn = isLoggedInP
}
}
And I have a World object
var navState = require('./navigation-state')
var NavigationStateManager = require('./navigation-state-manager')
var navigationStateManager = new NavigationStateManager()
function World() {
this.navState = simpleCopy(navState)
navigationStateManager.setState(this.navState)
}
function simpleCopy(objectToCopy) {
var copy = {}
for(var key in objectToCopy) {
copy[key] = objectToCopy[key]
}
return copy
}
In my steps file I do this
var World = require('../support/world')
module.exports = function() {
this.World = World
this.Given(...)
this.Then(...)
}
For some reason the state becomes undefined in the NavigationStateManager when the Given steps have been executed and the Then steps are being executed. When I log I can't see setState being called with an 'undefined' argument. I've had a different setup, putting the NavigationStateManager on the World object, but it gave me similar issues. Apparently the World object doesn't remain the same through all steps of a scenario, but how does it behave. The error seems to go against all JavaScript knowledge I have. Where do I put state in my tests?

All support files that export a function will be called with a context that exposes the following methods:
source: https://github.com/cucumber/cucumber-js/blob/master/docs/support_files/api_reference.md
I hadn't read this (and probably wouldn't have understood). I also confused the this reference to the context object and the this reference to a world object.
With context they mean the object that is exposed as this in the functions you export. It is the interface to interact with the Cucumber API.
This so called context object shouldn't be confused, with the world object. The world object is the this reference inside your steps, and is created by Cucumber from the World constructor you set on the context object (or the default if you don't set one) for every scenario.
Lastly you should not require and create new instances of any constructor exported in the support folder as I did. Since Cucumber automatically calls these constructors, you'll end up with two instances of the same object. Put your own helper objects, like a PageObject, in an separate folder.

View Model inheritance when using Durandal

I am building an application using Durandal and I have the need to share some functionality across view models.
I have 5 screens to build and they are all virtually the same screen except that in the activate function they will call to a different api end points but otherwise the view and view models will be identical.
Is there a pattern that I should be following to structure this correctly to promote code reuse?

If the views and the view models are identical except for calling different api actions, what about just taking in a parameter as part of the route? Then in the activate function, you can switch on the parameter. The route values can be designated so that your url is relevant, like [http://site/page/subtype], where subtype is the parameter (instead of using numeric values)
Regarding inheritance, depending on the features you need, there's so many ways to do JavaScript inheritance it can be a little confusing. There are some full-featured inheritance models provided by libraries such as base2 and Prototype. John Resig also has an inheritance model that I've used successfully.
In general, I prefer to stick to simpler solutions when it comes to JS inheritance. If you need a pretty much the full set of inheritance features, those libraries are good to consider. If you only really care about accessing a set of properties and functions from a base class, you might be able to get by with just defining the view model as a function, and replacing the function's prototype with the desired base class. Refer to Mozilla's Developer Docs for good info on inheritance.
Here's a sample:
//viewModelBase
define(function (require) {
"use strict";
function _ctor() {
var baseProperty = "Hello from base";
function baseFunction() {
console.log("Hello from base function");
}
//exports
this.baseProperty = baseProperty;
this.baseFunction = baseFunction;
};
//return an instance of the view model (singleton)
return new _ctor();
});
//view model that inherits from viewModelBase
define(function (require) {
"use strict";
function _ctor() {
var property1 = "my property value";
function activate() {
//add start up logic here, and return true, false, or a promise()
return true;
}
//exports
this.activate = activate;
this.property1 = property1;
};
//set the "base"
var _base = require("viewModelBase");
_ctor.prototype = _base;
_ctor.prototype.constructor = _ctor;
//return an instance of the view model (singleton)
return new _ctor();
});
Keep in mind this example all results in what effectively is a singleton (i.e. you'll only get the same instance, no matter how many times you require() it)
If you want a transient (non-singleton) just return _ctor. Then you'll need to instantiate a new instance after you require() it.
One more note, in general, functions should be defined on the prototype, not within the constructor function itself. See this link for more information on why. Because this example results in only a single instance, it's a moot point, so the functions are inside the constructor for improved readability and also the ability to access the private vars and functions.

Using inheritance in meteor.js

I've been hoping to use inheritance in Meteor, but I couldn't find anything about it in the documentation or on Stack Overflow.
Is it possible to have templates inheriting properties and methods from another abstract template, or class?

I think the short answer is no, but here's a longer answer:
One thing I've done to share functionality among templates is to define an object of helpers, and then assign it to multiple templates, like so:
var helpers = {
displayName: function() {
return Meteor.user().profile.name;
},
};
Template.header.helpers(helpers);
Template.content.helpers(helpers);
var events = {
'click #me': function(event, template) {
// handle event
},
'click #you': function(event, template) {
// handle event
},
};
Template.header.events(events);
Template.content.events(events);
It's not inheritance, exactly, but it does enable you to share functionality between templates.
If you want all templates to have access to a helper, you can define a global helper like so (see https://github.com/meteor/meteor/wiki/Handlebars):
Handlebars.registerHelper('displayName',function(){return Meteor.user().profile.name;});

I've answered this question here. While the solution doesn't use inheritance, it allow you to share events and helpers across templates with ease.
In a nutshell, I define an extendTemplate function which takes in a template and an object with helpers and events as arguments:
extendTemplate = (template, mixin) ->
helpers = ({name, method} for name, method of mixin when name isnt "events")
template[obj.name] = obj.method for obj in helpers
if mixin.events?
template.events?.call(template, mixin.events)
template
For more details and an example see my other answer.

Recently, I needed the same functionality in my app so I've decided to create my own package that will do that job out of the box. Although it's still work in progress, you can give it a go.
Basically, the entire method is as follows:
// Defines new method /extend
Template.prototype.copyAs = function (newTemplateName) {
var self = this;
// Creating new mirror template
// Copying old template render method to keep its template
var newTemplate = Template.__define__(newTemplateName, self.__render);
newTemplate.__initView = self.__initView;
// Copying helpers
for (var h in self) {
if (self.hasOwnProperty(h) && (h.slice(0, 2) !== "__")) {
newTemplate[h] = self[h];
}
}
// Copying events
newTemplate.__eventMaps = self.__eventMaps;
// Assignment
Template[newTemplateName] = newTemplate;
};
In your new template (new_template.js) in which you want to extend your abstract one, write following:
// this copies your abstract template to your new one
Template.<your_abstract_template_name>.copyAs('<your_new_template_name>');
Now, you can simply either overwrite your helpers or events (in my case it's photos helper), by doing following:
Template.<your_new_template_name>.photos = function () {
return [];
};
Your will refer to overwritten helper methods and to abstract ones that are not overwritten.
Note that HTML file for new template is not necessary as we refer to abstract one all the time.
Source code is available on Github here!

In Ember.js, how do you hook an object into a generic application namespace

Let's say I declared an application namespace:
App = Ember.Application.create();
and later I write an arrayController instance that creates objects and hook it onto the app namespace on user event:
App.objController = Ember.ArrayController.create({
content: [],
createObj: function(){
// instantiate new object
var newObj = Ember.Object.create({ ... })
//give obj a name
var newObjName = this._getObjName( someParam );
// hook object to an app namespace -> this is where I have an issue
App[newObjName] = newObj
},
...
});
See I explicitly use App[newObjName] = newObj to hook the object onto the namespace, ideally I would like some sort of generic way to name the application namespace in case I use the objController for a different application later.
There has to be some way to do this though I am just not familiar enough with Ember to have encountered it.
Note: on a scale of 1 to JFGI, this question is definitely not a 1. On the other hand it's a free resolved checkmark for anyone that has a moment.

During the initialization phase, Ember will instantiate all of your controllers and inject three properties into each of them - "target", "controllers", "namespace". The "namespace" property is your application.
That said, instead of hard-coding the top-level object:
App[newObjName] = newObj
you can do the following:
this.get("namespace").set(newObjName, newObj);
Note - in order for this to work, your application needs a router. Also, you should define controller classes, not instances. Ember will instantiate all controllers for you. So, this
App.objController = Ember.ArrayController.create({/* code here */});
should be written as
App.ObjController = Ember.ArrayController.extend({/* code here */});
Note the capital "O" in "ObjController".

Consider using injections, which is the preferred way to add dependencies.
Ember.Application.registerInjection({
name: 'fooObject',
before: 'controllers',
injection: function(app, router, property) {
if (property === 'FooObject') {
app.set('fooObject', app[property].create());
}
}
});
So if you define a class as follows:
App.FooObject = Ember.Object.extend({
// ...
});
the injection will create an instance into App.fooObject. Although we still use the namespace App, however only once. You could further do:
Ember.FooObject = Ember.Object.extend({
// ...
});
and then in your App, App.FooObject = Ember.FooObject but I'm not sure if its useful.

Dependency Injection with RequireJS

How much can I stretch RequireJS to provide dependency injection for my app? As an example, let's say I have a model that I want to be a singleton. Not a singleton in a self-enforcing getInstance()-type singleton, but a context-enforced singleton (one instance per "context"). I'd like to do something like...
require(['mymodel'], function(mymodel) {
...
}
And have mymodel be an instance of the MyModel class. If I were to do this in multiple modules, I would want mymodel to be the same, shared instance.
I have successfully made this work by making the mymodel module like this:
define(function() {
var MyModel = function() {
this.value = 10;
}
return new MyModel();
});
Is this type of usage expected and common or am I abusing RequireJS? Is there a more appropriate way I can perform dependency injection with RequireJS? Thanks for your help. Still trying to grasp this.

This is not actually dependency injection, but instead service location: your other modules request a "class" by a string "key," and get back an instance of it that the "service locator" (in this case RequireJS) has been wired to provide for them.
Dependency injection would involve returning the MyModel constructor, i.e. return MyModel, then in a central composition root injecting an instance of MyModel into other instances. I've put together a sample of how this works here: https://gist.github.com/1274607 (also quoted below)
This way the composition root determines whether to hand out a single instance of MyModel (i.e. make it singleton scoped) or new ones for each class that requires it (instance scoped), or something in between. That logic belongs neither in the definition of MyModel, nor in the classes that ask for an instance of it.
(Side note: although I haven't used it, wire.js is a full-fledged dependency injection container for JavaScript that looks pretty cool.)
You are not necessarily abusing RequireJS by using it as you do, although what you are doing seems a bit roundabout, i.e. declaring a class than returning a new instance of it. Why not just do the following?
define(function () {
var value = 10;
return {
doStuff: function () {
alert(value);
}
};
});
The analogy you might be missing is that modules are equivalent to "namespaces" in most other languages, albeit namespaces you can attach functions and values to. (So more like Python than Java or C#.) They are not equivalent to classes, although as you have shown you can make a module's exports equal to those of a given class instance.
So you can create singletons by attaching functions and values directly to the module, but this is kind of like creating a singleton by using a static class: it is highly inflexible and generally not best practice. However, most people do treat their modules as "static classes," because properly architecting a system for dependency injection requires a lot of thought from the outset that is not really the norm in JavaScript.
Here's https://gist.github.com/1274607 inline:
// EntryPoint.js
define(function () {
return function EntryPoint(model1, model2) {
// stuff
};
});
// Model1.js
define(function () {
return function Model1() {
// stuff
};
});
// Model2.js
define(function () {
return function Model2(helper) {
// stuff
};
});
// Helper.js
define(function () {
return function Helper() {
// stuff
};
});
// composition root, probably your main module
define(function (require) {
var EntryPoint = require("./EntryPoint");
var Model1 = require("./Model1");
var Model2 = require("./Model2");
var Helper = require("./Helper");
var entryPoint = new EntryPoint(new Model1(), new Model2(new Helper()));
entryPoint.start();
});

If you're serious about DI / IOC, you might be interested in wire.js: https://github.com/cujojs/wire
We use a combination of service relocation (like Domenic describes, but using curl.js instead of RequireJS) and DI (using wire.js). Service relocation comes in very handy when using mock objects in test harnesses. DI seems the best choice for most other use cases.

Not a singleton in a self-enforcing getInstance()-type singleton, but
a context-enforced singleton (one instance per "context").
I would recommend it only for static objects. It's perfectly fine to have a static object as a module that you load using in the require/define blocks. You then create a class with only static properties and functions. You then have the equivalent of the Math Object that has constants like PI, E, SQRT and functions like round(), random(), max(), min(). Great for creating Utility classes that can be injected at any time.
Instead of this:
define(function() {
var MyModel = function() {
this.value = 10;
}
return new MyModel();
});
Which creates an instance, use the pattern for a static object (one where values are always the same as the Object never gets to be instantiated):
define(function() {
return {
value: 10
};
});
or
define(function() {
var CONSTANT = 10;
return {
value: CONSTANT
};
});
If you want to pass an instance (the result of using a Module that have return new MyModel();), then, within an initialize function, pass a variable that capture the current state / context or pass on the Object that contains information on state / context that your modules needs to know about.