citizen

citizen

citizen is an event-driven MVC framework for Node.js web applications. Its purpose is to handle serving, routing, and event emitter creation, while providing some useful helpers to get you on your way. The nuts and bolts of your application are up to you, but citizen favors convention over configuration; those conventions are covered throughout this guide.

citizen is in beta. Your comments, criticisms, and requests are welcome.

citizen's static file serving is just a hack to get your dev environment up and running quickly. I recommend something like nginx as a front end for static file serving in your production environment.

Getting Started with citizen

Installing citizen

$ npm install citizen

Application Directory Structure

Here's the most basic directory structure of a citizen web app:

app/
  patterns/
    controllers/
      index.js
    models/
      index.js
    views/
      index/
        index.hbs // You can use Handlebars (.hbs), Jade (.jade), or HTML files
  start.js
public/

Here's a more complex app example (more about config and on directories below):

app/
  config/
    citizen-local.json
    citizen-production.json
    db.json
  logs/
  on/
    application.js
    request.js
    response.js
    session.js
  patterns/
    controllers/
      index.js
    models/
      index.js
    views/
      index/
        index.hbs
        index-alt.hbs
  start.js
public/

Configuration

citizen tries to follow convention over configuration whenever possible, but some things are best handled by a config file.

The config directory is optional and contains configuration files for both citizen and your app in JSON format. You can have multiple citizen configuration files within this directory, allowing different configurations based on environment. citizen retrieves its configuration file from this directory based on the following logic:

1. citizen parses each JSON file whose name starts with "citizen" looking for a "hostname" key that matches the machine's hostname. If it finds one, it loads that configuration.
2. If it can't find a matching hostname key, it looks for a file named citizen.json and loads that configuration.
3. If it can't find citizen.json, it runs under its default configuration.

citizen also parses any other files it finds in this directory and stores the resulting configuration within app.config. Using the file structure above, you'd end up with app.config.citizen and app.config.db.

The following represents citizen's default configuration.

{
  "mode": "production",
  "directories":  {
    "app": "[absolute path to start.js]",
    "logs": "[directories.app]/logs",
    "on": "[directories.app]/on",
    "patterns":  "[directories.app]/patterns",
    "public": "[directories.app]../public"
  },
  "urlPaths":  {
    "app":   "/",
    "fileNotFound": "/404.html"
  },
  "logs": {
    "console": true,
    "file": false
  },
  "httpPort": 80,
  "sessions": false,
  "sessionTimeout": 1200000
  "requestTimeout": 30000
  "mimeTypes": [parsed from internal config],
  "debug": {
    "output": "console",
    "depth": 2
  }
}

urlPaths.app is the folder path in your app's web address. If your app's URL is:

http://www.website.com/path/my-app

urlPaths.app should be "/path/my-app". This is necessary for the router to work.

Initializing citizen and starting the web server

The start.js file in your app directory can be as simple as this:

// start.js

app = require('citizen');

app.start();

From the command line:

$ node start.js

Objects returned by citizen
app.start()	Starts the web server
app.listen()	Your app's event listener for one or many asynchronous functions (see the listen() section)
app.controllers	Contains controllers from your supplied patterns, which you can use instead of require
app.models	Contains models from your supplied patterns, which you can use instead of require
app.views	Contains views (both raw and compiled) from your supplied patterns
app.helpers	Functions citizen uses internally that you might find helpful in your own app
app.handlebars	A pointer to the citizen Handlebars global, allowing you full access to Handlebars methods such as app.handlebars.registerHelper()
app.jade	A pointer to the citizen Jade global
app.config	The configuration settings you supplied at startup, which you can use within your application
CTZN	The global namespace used by citizen for session storage, among other things. You should not access or modify this namespace directly; anything you might need in your application will be exposed by the server to your controllers through local scopes.

Routing and URLs

Apps using citizen have a simple URL structure that determines which controller to fire, passes URL parameters, and makes a bit of room for SEO-friendly content. The structure looks like this:

http://www.site.com/controller-name/SEO-content-here/parameter/value/parameter2/value2

For example, let's say your site's base URL is:

http://www.cleverna.me

Requesting that URL will cause the index controller to fire, because the index controller is the default. The following URL will also cause the index controller to fire:

http://www.cleverna.me/index

If you have an article controller, you'd request it like this:

http://www.cleverna.me/article

Instead of query strings, citizen uses an SEO-friendly method of passing URL parameters consisting of name/value pairs. If you had to pass an article ID of 237 and a page number of 2, you'd append name/value pairs to the URL:

http://www.cleverna.me/article/id/237/page/2

Valid parameter names must start with a letter or underscore and may contain numbers.

citizen also lets you optionally insert relevant content into your URLs, like so:

http://www.cleverna.me/article/My-Clever-Article-Title/page/2

This SEO content must always follow the pattern name and precede any name/value pairs. You can access it via a URL parameter called descriptor, which means you can use it as a unique identifier (more on URL parameters below).

MVC Patterns

citizen relies on a simple model-view-controller convention. The article pattern mentioned above might use the following structure:

app/
  patterns/
    controllers/
      article.js
    models/
      article.js
    views/
      article/        // Matches the controller name
        article.hbs   // Matches the controller name, making it the default view
        edit.hbs      // Secondary view for editing an article

At least one controller is required for a given URL, and a controller's default view directory and default view file must share its name. Additional views should reside in this same directory. More on views in the Views section.

Models and views are optional and don't necessarily need to be associated with a particular controller. If your controller doesn't need a model, you don't need to create one. If your controller is going to pass its output to another controller for further processing and final rendering, you don't need to include a matching view. (See the controller handoff directive.)

Controllers

Each controller requires at least one public function named handler():

// article controller

exports.handler = handler;

function handler(params, context, emitter) {

  // do some stuff

  emitter.emit('ready', {
    // content and directives for the server
  });
}

The citizen server calls handler() after it processes the initial request and passes it 3 arguments: an object containing the parameters of the request, the current request's context generated by the app up to this point, and an emitter for the controller to emit when it's ready to pass the results to the server.

Contents of the params argument
request	The request object generated by the server, just in case you need direct access
response	The response object generated by the server
route	Details of the route, such as the requested URL and the name of the route (controller)
url	Any URL parameters that were passed including the descriptor, if provided
form	Data collected from a POST
payload	Data collected from a PUT
cookie	An object containing any cookies that were sent with the request
session	An object containing any session variables, if sessions are enabled

In addition to having access to these objects within your controller, they are also included in your view context automatically so you can reference them within your view templates as local variables (more details in the Views section).

For example, based on the previous article URL...

http://www.cleverna.me/article/My-Clever-Article-Title/page/2

...you'll have the following params.url object passed to your controller:

{
  page: 2,
  descriptor: 'My-Clever-Article-Title'
}

The context argument contains any output that's been generated by the request up to this point. There are various events that can populate this argument with content and directives, which are then passed to your controller so you can access that content or see what directives have been set by previous events. More on this later.

The emitter argument is the method by which the controller lets the server know that it's done with its tasks and ready to render the result. The emitter should emit a "ready" event when the controller has accomplished its task. This lets the server know it's okay to proceed.

Using the above URL parameters, I can retrieve the article content from the model and pass it back to the server:

// article controller

exports.handler = handler;

function handler(params, context, emitter) {
  // Get the article content
  var content = {
    article: app.models.article.getArticle(params.url.descriptor, params.url.page)
  };

  // Emit the 'ready' event and pass the view context back to the server for
  // rendering via the content object
  emitter.emit('ready', {
    content: content
  });
};

The second argument in emitter.emit is an object containing any data you want to pass back to citizen. All the content you want to render in your view should be passed to citizen within an object called content, as shown above. Additional objects can be passed to citizen to perform other directives (explained later in the Emitter Directives section).

Models

Models are optional and their structure is completely up to you. citizen doesn't talk to your models directly; it only stores them in app.models for your convenience.

Here's a simple static model for the article pattern:

// article model

exports.getArticle = getArticle;

function getArticle(descriptor, page) {
  var articles = {
    'My-Clever-Article-Title': {
      title: 'My Clever Article Title',
      summary: 'Am I not terribly clever?',
      pages: {
        '1': 'First page content',
        '2': 'Second page content'
      }
    },
    'Clever-Part-II-The-Sequel': {
      title: 'Clever Part II: The Sequel',
      summary: 'Too clever for just one article.',
      pages: {
        '1': 'First page content',
        '2': 'Second page content'
      }
    }
  };

  return {
    title: articles[descriptor]['title'],
    summary: articles[descriptor]['summary'],
    text: articles[descriptor]['pages'][page]
  };
};

Views

citizen supports Handlebars and Jade templates, as well as good old HTML. You can even mix and match Handlebars, Jade, and HTML templates as you see fit; just use the appropriate file extensions (.hbs, .jade, or .html) and citizen will compile and render each view with the appropriate engine.

You have direct access to each engine's methods via app.handlebars and app.jade, allowing you to use methods like app.handlebars.registerHelper() to create global helpers. Keep in mind that you're extending the global Handlebars and Jade objects, potentially affecting citizen's view rendering if you do anything wacky because citizen relies on these same objects.

In article.hbs, you can reference objects you placed within the content object passed by the emitter. citizen also injects the params object into your view context automatically, so you have access to those objects as local variables (such as the url scope):

<!DOCTYPE html>
<html>
<body>
  <h1>
    {{article.title}} - Page {{url.page}}
  </h1>
  <p id="summary">
    {{article.summary}}
  </p>
  <div id="text">
    {{article.text}}
  </div>
</body>
</html>

citizen sends HTML to the client by default, but you can also return JSON and JSONP with no extra work on your part.

JSON

You don't need a custom view just for JSON. You can tell a controller to return its content as plain text JSON by adding the format URL parameter.

http://www.cleverna.me/article/My-Clever-Article-Title/page/2/format/json

Returns...

{
  "My-Clever-Article-Title": {
    "title": "My Clever Article Title",
    "summary": "Am I not terribly clever?",
    "text": "Second page content"
  }
}

Whatever you've added to the controller's emitter content object will be returned. The line breaks are just for readability. The actual output is compressed.

JSONP

JSONP is pretty much the same. Use format and callback in the URL:

http://www.cleverna.me/article/My-Clever-Article-Title/page/2/format/jsonp/callback/foo

Returns:

foo({
  "My-Clever-Article-Title": {
    "title": "My Clever Article Title",
    "summary": "Am I not terribly clever?",
    "text": "Second page content"
  }
});

If you want to make it available to third party sites, see the CORS section.

Rendering alternate views

By default, the server renders the view whose name matches that of the controller. To render a different view, use the view directive in your emitter.

app.listen({ functions }, callback)

The article example we've been using has only simple methods that return static content immediately, but things are rarely that simple. The listen() function takes advantage of the asynchronous, event-driven nature of Node.js, letting you wrap a single function or multiple asynchronous functions within it and firing a callback when they're done. You can also chain and nest multiple listen() functions for very powerful asynchronous function calls.

listen() takes two arguments: an object containing one or more methods you want to call, and a callback to handle the output. listen() requires that your functions be written to accept an emitter argument, which is how your function notifies listen() that it's ready.

Let's say our article model has two methods that need to be called before returning the results to the controller. One is called getArticle() and the other is getViewers(). Assume that both methods make an asynchronous call to a database and won't be able to return their output immediately, so we have to listen for when they're ready and then react.

// article controller

exports.handler = handler;

function handler(params, context, emitter) {
  app.listen({
    // The property contains the action you want to listen for, which is
    // wrapped in an anonymous function in order to pass the emitter
    article: function (emitter) {
      app.models.article.getArticle({ id: params.url.id, page: params.url.page }, emitter);
    },
    viewers: function (emitter) {
      app.models.article.getViewers(params.url.id, emitter);
    }
  }, function (output) {
    // The property names you assign to the methods above become the names
    // of the output objects
    var content = {
          article: output.article,
          viewers: output.viewers
        };

    // Emit `ready` now that we have the handler output and pass the
    // context back to the server
    emitter.emit('ready', {
      content: content
    });
  });
}

And the model:

// article model

module.exports = {
  getArticle: getArticle,
  getViewers: getViewers
};

function getArticle(args, emitter) {
  app.db.article(args, function (data) {
    // When the database returns the data, emit `ready` and pass the
    // data back to listen()
    emitter.emit('ready', data);
  });
};

function getViewers(id, emitter) {
  app.db.viewers(id, function (data) {
    // When the database returns the data, emit `ready` and pass the
    // data back to listen()
    emitter.emit('ready', data);
  });
};

listen() currently fires all functions asynchronously and returns the results for every function in a single output object after all functions have completed. A waterfall-type execution is being worked on, but in the meantime, you can nest listen() functions to achieve the same effect:

listen({
  first: function (emitter) {
    doSomething(emitter);
  }
}, function (output) {
  listen({
    second: function (emitter) {
      doNextThing(output.first, emitter);
    }
  }, function (output) {
    listen({
      third: function (emitter) {
        doOneMoreThing(output.second, emitter);
      }
    }, function (output) {
      thisIsExhausting(output.third);
    });
  });
});

Emitter Directives

In addition to the view content, the controller's ready emitter can also pass directives to render alternate views, set cookies and session variables, initiate redirects, call and render includes, and hand off the request to another controller for further processing.

Views

By default, the server renders the view whose name matches that of the controller. To render a different view, use the view directive in your emitter:

// article controller

exports.handler = handler;

function handler(params, context, emitter) {
  app.listen({
    article: function (emitter) {
        app.models.article.getArticle({ id: params.url.id, page: params.url.page }, emitter);
    }
  }, function (output) {
    var content = {
          article: output.article
        };

    emitter.emit('ready', {
      content: content,
      // This tells the server to render app/patterns/views/article/edit.hbs
      view: 'edit'
    });
  });
}

Cookies

You set cookies by appending a cookie object to the emitter context. Cookies can be set one at a time or in groups. The following code tells the server to set username and passwordHash cookies that never expire:

// login controller

exports.handler = handler;

function handler(params, context, emitter) {
  app.listen({
    login: function (emitter) {
      app.models.login.authenticate({
        // Form values, just like URL parameters, are passed via the params
        // argument
        username: params.form.username,
        password: params.form.password
      }, emitter);
    }
  }, function (output) {
    var content = {
          login: output.login
        },
        cookie;

    if ( content.login.success ) {
      cookie = {
        // The cookie gets its name from the property name
        username: {
          // The cookie value
          value: content.login.username,

          // Valid expiration options are:
          // 'now' - deletes an existing cookie
          // 'never' - current time plus 30 years, so effectively never
          // 'session' - expires at the end of the browser session (default)
          // [time in milliseconds] - length of time, added to current time
          expires: 'never'
        },
        passwordHash: {
          value: content.login.passwordHash,
          expires: 'never'
        }
      };
    }

    emitter.emit('ready', {
      content: content,
      cookie: cookie
    });
  });
};

The following code sets the same cookies, but they expire at the end of the browser session:

cookie.username = content.login.username;
cookie.passwordHash = content.login.passwordHash;

Other cookie options include path (default is /), httpOnly (default is true for security reasons), and secure (default is false).

Cookies sent by the client are available in params.cookie within the controller and simply cookie within the view context:

<!DOCTYPE html>
<html>
<body>
  <div id="welcome">
    {{#if cookie.username}}
      Welcome, {{cookie.username}}.
    {{else}}
      <a href="/login">Login</a>
    {{/if}}
  </div>
</body>
</html>

Cookie variables you set within your controller aren't immediately available within the params.cookie scope. citizen's server has to receive the response from the controller before it can send the cookie to the client, so use a local instance of the variable if you need to access it during the same request.

Session Variables

If sessions are enabled, citizen creates an object called CTZN.sessions to store session information. Don't access this object directly; use params.session instead (or simply session within the view). These local scopes reference the current user's session.

By default, the session has two properties: id and expires. The session ID is also sent to the client as a cookie called ctzn_session_id.

Setting session variables is the same as setting cookie variables:

session.username = 'Danny';
session.nickname = 'Doc';

emitter.emit('ready', {
  content: content,
  session: session
});

To forcibly clear and expire the current user's session:

session.expires = 'now';

This won't end the session immediately. citizen has to receive your controller's response before it can act on this directive.

Like cookies, session variables you've just assigned aren't available during the same request within the params.session scope, so use a local instance if you need to access this data right away.

Redirects

You can pass redirect instructions to the server that will be initiated after the request is complete. Redirects using this method are not immediate, so the controller will do everything it's been asked to do before the redirect is processed. The user agent won't receive a full response, however. No view content will be sent, but cookies and session variables will be set if specified.

The redirect object takes two properties: statusCode and url. If you don't provide a status code, citizen uses 302 (temporary redirect).

redirect = {
  statusCode: 301,
  url: 'http://redirect.com'
};

emitter.emit('ready', {
  content: content,
  redirect: redirect
});

Includes

citizen has a standardized way of handling includes that works in both Handlebars and Jade templates. In citizen, includes are more than just chunks of code that you can reuse. citizen includes are full patterns, each having its own controller, model, and view(s).

Let's say our article pattern's Handlebars template has the following contents:

<!DOCTYPE html>
<html>
<head>
  <title>{{metaData.title}}</title>
  <meta name="description" content="{{metaData.description}}" />
  <meta name="keywords" content="{{metaData.keywords}}" />
  <link rel="stylesheet" type="text/css" href="app.css" />
</head>
<body>
  <header>
    <a id="logo">Home page</a>
    <nav>
      <ul>
        <li>
          <a href="/">Home</a>
        </li>
        <li>
          <a href="/articles">Settings</a>
        </li>
      </ul>
    </nav>
  </header>
  <main>
    <h1>
      {{article.title}}
    </h1>
    <p id="summary">
      {{article.summary}}
    </p>
    <div id="text">
      {{article.text}}
    </div>
  </main>
  <footer>
    Copyright &copy; 2014 cleverna.me
  </footer>
</body>
</html>

It probably makes sense to use includes for the head section, header, and footer because you'll use that code everywhere. Let's create patterns for these includes. I like to follow the convention of starting partials with an underscore, but that's up to you:

app/
  patterns/
    controllers/
      _footer.js
      _head.js
      _header.js
      article.js
    models/
      _head.js   // The header and footer are just static HTML, so they need no models
      article.js
    views/
      _footer/
        _footer.html
      _head/
        _head.hbs
      _header/
        _header.html
        _header-authenticated.html // A different header for logged in users
      article/
        article.hbs

When the article controller is fired, it needs to tell citizen which includes it needs. We do that with the include directive, which we pass via the context in the emitter:

// article controller

exports.handler = handler;

function handler(params, context, emitter) {
  app.listen({
    article: function (emitter) {
        app.models.article.getArticle({ id: params.url.id, page: params.url.page }, emitter);
    },
    viewers: function (emitter) {
      app.models.article.getViewers(params.url.id, emitter);
    }
  }, function (output) {
    var content = {
          article: output.article,
          viewers: output.viewers
        };

    emitter.emit('ready', {
      content: content,
      include: {
        // The property name is the name of the include's controller.
        // The property value is the name of the view.
        _head: '_head',
        _header: '_header',
        _footer: '_footer'
      }
    });
  });
}

This tells citizen to call the _head, _header, and _footer controllers, render their respective views, and add them to the view context. In article.hbs, we now reference the includes using the include object. The include object contains rendered HTML views, so use triple-stache in Handlebars to skip escaping:

<!DOCTYPE html>
<html>
{{{include._head}}}
<body>
  {{{include._header}}}
  <main>
    <h1>
      {{article.title}}
    </h1>
    <p id="summary">
      {{article.summary}}
    </p>
    <div id="text">
      {{article.text}}
    </div>
  </main>
  {{{include._footer}}}
</body>
</html>

What if logged in users get a different header? Just tell citizen to use a different view:

emitter.emit('ready', {
  content: content,
  include: {
    _head: '_head',
    _header: '_header-authenticated',
    _footer: '_footer'
  }
});

Includes can generate content and add it to the view context of your primary controller (article.js in this example) because the primary view is the last to be rendered. However, includes are called and rendered asynchronously, so while your _header controller can generate content and add it to the view context of your article controller, don't assume that your _footer controller will have access to that data. (The option of waterfall execution is being worked on, so this is only true for the time being.)

Currently, if a controller is requested as an include, any of the directives to set cookies, session variables, redirects, etc. are ignored, but it's on the feature list to get these working.

A pattern meant to be used as an include can be accessed via URL just like any other controller. You could request the _head controller like so:

http://cleverna.me/_head

Perhaps you'd have it return meta data as JSON for the article pattern:

http://cleverna.me/_head/for/article/title/My-Clever-Article-Title/format/json

Here's an example of the _head controller written as both an include and a handler of direct requests:

// _head controller

exports.handler = handler;

function handler(params, context, emitter) {
  var metaData,
      // If the "for" URL param exists, use that. Otherwise, assume _head is being used
      // as an include and use the requested route name.
      getMetaDataFor = params.url.for || params.route.name;

  // If it's for the article pattern, call getMetaData() and pass it the title
  if ( getMetaDataFor === 'article' && params.url.title ) {
    metaData = app.models.article.getMetaData(params.url.title);
  // Otherwise, check if the requested controller's model has getMetaData()
  } else if ( app.models[getMetaDataFor] && app.models[getMetaDataFor].getMetaData ) {
    metaData = app.models[getMetaDataFor].getMetaData();
  }

  emitter.emit('ready', {
    content: {
      metaData: metaData
    }
  });
}

Of course, if you don't write the controller in a manner to accept direct requests and return content, it'll return nothing (or throw an error).

Note: A convention is being worked on to let you make controllers private, so even if they're requested, they'll return a 404. You'll have to do this manually for now.

Controller Handoff

citizen allows the requested controller to give another controller the responsibility of handling the request and rendering its own view via a directive called handoff. The requested controller passes its content and directives to a secondary controller, which assumes responsibility for the request, adding its own content and directives, and rendering its own view.

A common use case for handoff would be to create a layout controller that serves as a template for every page on your site, rendering all the includes necessary and leaving only the core content and markup to the requested controller. Let's modify the article controller and view so it hands off rendering responsibility to a separate layout controller:

// article controller

exports.handler = handler;

function handler(params, context, emitter) {
  app.listen({
    article: function (emitter) {
      app.models.article.getArticle({ id: params.url.id, page: params.url.page }, emitter);
    },
    viewers: function (emitter) {
      app.models.article.getViewers(params.url.id, emitter);
    }
  }, function (output) {
    var content = {
          article: output.article,
          viewers: output.viewers
        };

    emitter.emit('ready', {
      content: content,
      handoff: {
        controller: 'layout',
        // Specifying the view is optional. The layout controller will use
        // its default view unless you tell it to use a different one.
        view: 'layout'
      }
    });
  });
}

The layout controller handles the includes and renders its own view:

// layout controller

exports.handler = handler;

function handler(params, context, emitter) {
  emitter.emit('ready', {
    // No need to specify `content` here because citizen keeps track of the
    // article pattern's request context throughout the handoff process
    include: {
      _head: '_head',
      _header: '_header',
      _footer: '_footer'
    }
  });
}

When you use the handoff directive, the originally requested view (article in this case) is rendered as an include called _main:

<!-- article.hbs, which is saved into include._main -->
<h1>
  {{article.title}}
</h1>
<p id="summary">
  {{article.summary}}
</p>
<div id="text">
  {{article.text}}
</div>

And our layout.hbs file:

<!DOCTYPE html>
<html>
{{{include._head}}}
<body>
  {{{include._header}}}
  <main>
    {{{include._main}}}
  </main>
  {{{include._footer}}}
</body>
</html>

You can implement as many handoffs as you want (controller A can handoff to controller B, which can handoff to controller C, and so on), but the original controller's view will still be the one that ends up in includes._main.

Application Events and the Context Argument

Certain events will occur throughout the life of your citizen application. You can act on these application events, execute functions, set directives, and pass the results to the next event or your controller via the context argument. For example, you might set a custom cookie at the beginning of every new session, or check for cookies at the beginning of every request and redirect the user to a login page if they're not authenticated.

To take advantage of these events, include a directory called "on" in your app with the following modules and exports:

app/
  on/
    application.js // exports start(), end(), and error()
    request.js     // exports start() and end()
    response.js    // exports start() and end()
    session.js     // exports start() and end()

The application start() and request start() and end() events are triggered before your controller is fired, so the output from those events is passed to your controller via the context argument.

All files and exports are optional. citizen only calls them if they exist. For example, you could have only a session.js module that exports end().

Note: As of this version, session end() and application end() aren't functional. They'll be in a future version.

Here's an example of a request module that checks for a username cookie at the beginning of every request and redirects the user to a login page if it's not there, unless the requested pattern is the login page:

// app/on/request.js

exports.start = start;

function start(params, context, emitter) {
  var redirect = {};

  if ( !params.cookie.username && params.route.name !== 'login' ) {
    redirect.url = 'http://' + params.request.headers.host + '/login';
  }

  emitter.emit('ready', {
    redirect: redirect
  });
};

HTTP Access Control (CORS)

citizen supports cross-domain HTTP requests via access control headers. By default, all controllers respond to requests from the host only. To enable cross-domain access, add an access object with the necessary headers to your controller's exports:

module.exports = {
  handler: handler,
  access: {
    'Access-Control-Allow-Origin': 'http://www.somesite.com http://anothersite.com',
    'Access-Control-Expose-Headers': 'X-My-Custom-Header, X-Another-Custom-Header',
    'Access-Control-Max-Age': 1728000,
    'Access-Control-Allow-Credentials': 'true',
    'Access-Control-Allow-Methods': 'OPTIONS, PUT',
    'Access-Control-Allow-Headers': 'Content-Type',
    'Vary': 'Origin'
  }
};

For more details on CORS, check out this writeup on the Mozilla Developer Network.

Helpers

In addition to listen(), citizen includes a few more basic helper functions that it uses internally, but might be of use to you, so it returns them for public use.

copy(object)

Creates a deep copy of an object.

var myCopy = app.helpers.copy(myObject);

extend(object, extension[, boolean])

Extends an object with another object, effectively merging the two objects. By default, extend() creates a copy of the original before extending it, creating a new object. If your intention is to alter the original and create a pointer, pass the optional third argument of false.

var newObject = app.helpers.extend(originalObject, extensionObject);

isNumeric(object)

Returns true if the object is a number, false if not.

if ( app.helpers.isNumeric(url.id) ) {
  // pass it to the db
} else {
  return 'Naughty naughty...';
}

dashes(string)

Convert strings into SEO-friendly versions that you can use in your URLs.

var seoTitle = app.helpers.dashes("Won't You Read My Article?"); // 'Wont-You-Read-My-Article'

Debugging

Warning: debug and development modes are inherently insecure. Don't use them in a production environment.

If you set "mode": "debug" in your config file, citizen dumps the current pattern's output to the console by default. You can also dump it to the view with the ctzn_dump URL parameter:

http://www.cleverna.me/article/id/237/page/2/ctzn_dump/view

By default, the pattern's complete output is dumped. You can specify the exact object to debug with the ctzn_debug URL parameter. You can access globals, pattern, and server params:

// Dumps pattern.content to the console
http://www.cleverna.me/article/id/237/page/2/ctzn_debug/pattern.content

// Dumps the server params object to the console
http://www.cleverna.me/article/id/237/page/2/ctzn_debug/params

// Dumps CTZN.session to the console
http://www.cleverna.me/article/id/237/page/2/ctzn_debug/CTZN.session

// Dumps CTZN.session to the view
http://www.cleverna.me/article/id/237/page/2/ctzn_debug/CTZN.session/ctzn_dump/view

In development mode, you must specify the ctzn_debug URL parameter to enable debug output. Debug output is disabled in production mode.

If you always want debug output dumped to the view, set debug output to "view" in your citizen config file.

{
  "debug": {
    "output": "view"
  }
}