PVC – Page-View-Controller

[Oliver]

Introducing PVC

PvcCore: https://github.com/oliverwehn/PvcCore/

PvcRendererTwig: https://github.com/oliverwehn/PvcRendererTwig/ (coming soon)

PvcGenerator: https://github.com/oliverwehn/PvcGenerator/ (coming soon)

Each time I’ve built a ProcessWire page I’ve struggled with organizing (and separating) code, markup and stuff. Playing around with frameworks (backend as well as frontend) like Rails, Ember and stuff I really liked having a given structure, knowing where to put what piece of code. Therefor I started working on a MVCish way to deal with templates in PW that considers the $page object kind of the data/model layer and adds View and Controller upon it. First by just catching everything via a small processor file added to all PW templates as altFilename. I’ve digged a bit deeper since then and hooked into the native rendering process, have been refactoring my code base more than a dozen times. Now I got a first version that seem to work and I’d love some of you guys to try it out!

PVC (instead of MVC) stands for Page-View-Controller, as it considers PW’s $page var the model/data layer. I’m still working on the README.md on GitHub to document the basics. So have a look for more detailed infos there. I’ll give you a short overview here:

• Code separation: PVC introduces views and controllers to your PW templates as well as multiple action templates.
• Controllers, as most of you already know, keep all the business logic. Controllers execute actions wired to routes (urlSegment patterns). Even routes with dynamic segements (e.g. /edit/:id/) can be defined and assigned to an action, providing input through $this->input->route. Values can be set on the controller to be accessable in your templates later on. It’s also possible to set dynamic values as closures to be calculated (e.g. using field values of the current page) on render. Also controllers allow you to set layouts, styles and scripts to be available in your layout or template. Logic can be shared through inheritance between controllers.
• Views introduce view helpers. Helpers are functions that are made available to you (only) within your template context. There are predefined ones like embed(), snippet(), styles() or scripts(). But you can implement your own helpers easily and share them among your view classes through inheritance.
• Action templates contain the actual markup. Every action defined in a controller uses its own template. So the same page can display content accordingly to the action that was addressed via urlSegments/route. Within templates you can access all field values and values set on your controller like globals (e.g. <?=$title?>).
• Modular renderers: PVC implements rendering through separate renderer modules. PvcCore comes with PvcRendererNative that gives you template syntax the good ol’ PW/PHP way. A Twig renderer is in the making. And maybe you want to build your own renderer for the template syntax of your choice?

I consider the module an early Beta version. So make sure to try it within a save environment! Would love to get some feedback (and error reports). I’m no professional developer, so code quality may suck here and there. So I’m glad for inputs on that, too. Also there is some old stuff in there yet, I still have to get rid of.

[Michael Murphy]

Hi Oliver,

Thanks for sharing this, it's always interesting to see how others setup their projects.

Could you give an example of how this would be used in a typical project? Like a portfolio site or a simple online shop.

[Oliver]

Well, I’ll give you a short example to demonstrate how it all works together. Imagine the following simple setup:

Page Tree

Home
 |- Products (template=products)
 |   |- Product 1 (template=product)
 |   |- Product 2
 |   |- Product 3
 |   |- Product 4
 |   |- Product 5
 |
 |- ...

Page Products with template “products” is meant to show a gallery of product images. So we create a controller for the template (that otherwise would be auto-generated on the fly) in site/templates/controllers/ named products.controller.php.

<?php
/* site/templates/controllers/products.controller.php */
class ProductsController extends BaseController {

  // init() is executed on controller setup before action is called
  public function init() {
    // Just in case you defined general stuff in BaseController’s init() method
    parent::init();

    // Set (for all actions of this controller) a script 'jquery/my.jquery.plugin.js' in group 'footer' with priority 5
    // In layout and template you can then output the scripts group 'footer' using view helper <?=scripts('footer');?>
    // Assets defined via path are looked up in the corresponding folder within site/templates/assets/. You can alternatively
    // define assets using a URL.
    $this->script('jquery/my.jquery.plugin.js', 'footer', 5);

  }

  // index is the default action executed if no other route matches
  public function index() {
    // Add (for this action only) a stylesheet 'gallery.css' to group 'footer' with priority 10.
    // In layout and template you can then output the styles group using view helper <?=styles('footer');?>
    $this->style('gallery.css', 'footer', 10);

    // Set a template var 'products' that contains current page’s children as PageArray
    $this->set('products', $this->page->children('template=product, sort=title'));
  }
}

We’ll need an action template for products’ index action in site/templates/views/products/ named index.tmpl.php.

<!-- site/templates/views/products/index.tmpl.php -->
<h2><?=$title?></h2>

<ul class="products">
<?php foreach($products as $product) { ?>
  <li class="products__item <?=gridClass($product->images->first(), 'products__image');?>"><a href="<?=$product->url?>"><img src="<?=$product->images->first()->url;?>" alt="<?=$product->title;?>"></a></li>
<?php } ?>
</ul>

We’ll have a look at the used view helper gridClass() later.

The first page in PW’s page stack (the one rendered through processPageView directly) is rendered and outputted in a layout’s outlet. Layouts are stored in site/templates/layouts. There is a default layout default.tmpl.php preinstalled. The rendered action templates are outputted within the document structure by using <?=$outlet?>. You can add as many layouts as you want and change the layout the action template will be rendered in by setting another template within your controller’s init() method like this:

...

public function init() {
  parent::init();

  // use layout site/templates/layouts/shop.tmpl.php for this template
  $this->set('layout', 'shop');
}

... 

Our product template of course also gets a controller:

<?php
/* site/templates/controllers/product.controller.php */

class ProductController extends BaseController {

  public function init() {
    parent::init();   
    // assign route pattern with dynamic segment to action 'reviewVote'
    $this->route('/reviews/:id/vote/', array('id' => '^[0-9]+$'), 'reviewsVote');
  }
  
  public function index() {
    // set dynamic value to be calculated right before rendering the action template
    $this->set('similarProducts', function() {
      // your logic to get a PageArray of similar products goes here
      $tags = $this->page->get('tags'); 
      // or $tags = $this->get('tags'); as it will pass the request through to page, if 'tags' isn’t set on controller itself
      $similarProducts = ...;
      return $similarProducts;
    });
  }

  // action accessible via route /reviews/
  public function reviews() {
    // we should set up this for pagination in template settings
    $this->set('reviews', $this->pages->find("template=reviews, product={$this->page->id}"));
  }

  // action accessible via route /reviews/new/
  public function reviewsNew() {
    // Later versions will allow to handle actions depending on REQUEST_TYPE, but for now:
    if($_SERVER['REQUEST_METHOD'] == 'POST') {
      // create review logic goes here
      ...
      $this->session->redirect(...);
    }
    else {
      $this->set('form', $this->forms->get('review'));
    }
  }

  // action for action route /reviews/:id/vote/
  public function reviewsVote() {
    if($id = $this->input->route->id) {
      // save vote for review
      ...
    }
  }
}

Template product’s action templates go into site/templates/views/product/ named index.tmpl.php, reviews.tmpl.php, etc.

When we talk about routes in PVC, it means patterns of PW’s urlSegments. If you want to have multiple actions and routes, you have to enable urlSegments for the particular template. Index action is performed when a page is addressed directly via its path. If urlSegments are added to the request, PVC captures the urlSegments as a action route and provides it to the controller which determines the action to perform for the route.

Until now all template specific view classes (like ProductsView, ProductView) are generated on the fly. Let’s use some view helpers to reduce logic in templates. For example we want pagination looking all the same all over the site. Therefor we define a general view helper for that in site/templates/views/base.view.php.

<?php

class BaseView extends PvcView {

  /**
   * Add custom view helpers that will be available as
   * global functions within your templates.
   * @method customViewHelpers
   * @param Array $scope contains an associative array of template scope
   * @returns Array An associative array with key/closure pairs
   */
  public function customViewHelpers($scope) {
    return array(
      /**
       * Each helper is defined as a pair of key (name of the helper
       * function in template context) and closure (function body)
       * Via use() you can pass in $scope and custom values to be
       * available within your helper.
       * The helper below can be called like this: <?=sayHi('your name');?>
       */
      'pagination' => function(PageArray $pageArray) use($scope) {
        return $pageArray->renderPager(array(
          'nextItemLabel' => "Next",
          'previousItemLabel' => "Prev",
          'separatorItemClass' => "pagination__item--separator",
          'nextItemClass' => "pagination__item--next",
          'previousItemClass' => "pagination__item--prev",
          'currentItemClass' => "pagination__item--current",
          'lastItemClass' => "pagination__item--last",
          'listMarkup' => "<ul class='pagination pagination--{$scope['template']}'>{out}</ul>",
          'itemMarkup' => "<li class='pagination__item {class}'>{out}</li>",
          'linkMarkup' => "<a href='{url}'><span>{out}</span></a>"      
        ));
      })
    );
  }
}

Now you can render your pagination in your action templates just by passing a PageArray value to your pagination view helper like <?=pagination($reviews);?>.

You also can create template-specific view helpers (like gridClass() used in our products action template for index at the top) by creating a view class for the template in site/templates/views/ like this:

<?php
/* site/templates/views/products.view.php */

class ProductsView extends BaseView {

  public function customViewHelpers($scope) {
    $helpers = array(
      'gridClass' => function(PageImage $img, $class=null) {
        $w = $img->width();
        $h = $img->height();
        $orientation = 'square';
        if($w < $h) $orientation = 'portrait';
        if($w > $h) $orientation = 'landscape';
        return is_string($class) ? sprintf('%s--%s', $class, $orientation) : $orientation; 
      }
    );
    return array_merge($helpers, parent::customViewHelpers($scope));
  }
}

Predefined view helpers are for example embed() to render other pages within your current action template, scripts() and styles() to output asset groups and snippet() to render reusable code chunks stored in site/templates/snippets/ within the current action template’s scope.

Hopefully this gives you a vague idea how you can organize your code base using PVC. 

[fmgujju]

@Oliver: When I setup on ProcessWire 2.5.3 as you have mentioned above, I got following error:

Notice: Array to string conversion in C:\xampp\htdocs\pw25\wire\core\PageTraversal.php on line 72

Fatal error: Exception: Field does not exist: Arraysort (in C:\xampp\htdocs\pw25\wire\core\PageFinder.php line 494) #0 [internal function]: PageFinder->___getQuery(Object(Selectors), Array) #1 C:\xampp\htdocs\pw25\wire\core\Wire.php(389): call_user_func_array(Array, Array) #2 C:\xampp\htdocs\pw25\wire\core\Wire.php(344): Wire->runHooks('getQuery', Array) #3 C:\xampp\htdocs\pw25\wire\core\PageFinder.php(263): Wire->__call('getQuery', Array) #4 C:\xampp\htdocs\pw25\wire\core\PageFinder.php(263): PageFinder->getQuery(Object(Selectors), Array) #5 [internal function]: PageFinder->___find(Object(Selectors), Array) #6 C:\xampp\htdocs\pw25\wire\core\Wire.php(389): call_user_func_array(Array, Array) #7 C:\xampp\htdocs\pw25\wire\core\Wire.php(344): Wire->runHooks('find', Array) #8 C:\xampp\htdocs\pw25\wire\core\Pages.php(168): Wire->__call('find', Array) #9 C:\xampp\htdocs\pw25\wire\core\Pages.php(168): PageFinder->find(Object(Selectors), Array) #10 [internal function]: Pages->___find('parent_id=1013,...', Array) #11 C:\xampp\htdo inC:\xampp\htdocs\pw25\index.php on line 226

Error: Exception: Field does not exist: Arraysort (in C:\xampp\htdocs\pw25\wire\core\PageFinder.php line 494)

#0 [internal function]: PageFinder->___getQuery(Object(Selectors), Array)
#1 C:\xampp\htdocs\pw25\wire\core\Wire.php(389): call_user_func_array(Array, Array)
#2 C:\xampp\htdocs\pw25\wire\core\Wire.php(344): Wire->runHooks('getQuery', Array)
#3 C:\xampp\htdocs\pw25\wire\core\PageFinder.php(263): Wire->__call('getQuery', Array)
#4 C:\xampp\htdocs\pw25\wire\core\PageFinder.php(263): PageFinder->getQuery(Object(Selectors), Array)
#5 [internal function]: PageFinder->___find(Object(Selectors), Array)
#6 C:\xampp\htdocs\pw25\wire\core\Wire.php(389): call_user_func_array(Array, Array)
#7 C:\xampp\htdocs\pw25\wire\core\Wire.php(344): Wire->runHooks('find', Array)
#8 C:\xampp\htdocs\pw25\wire\core\Pages.php(168): Wire->__call('find', Array)
#9 C:\xampp\htdocs\pw25\wire\core\Pages.php(168): PageFinder->find(Object(Selectors), Array)
#10 [internal function]: Pages->___find('parent_id=1013,...', Array)
#11 C:\xampp\htdo
This error message was shown because site is in debug mode ($config->debug = true; in /site/config.php). Error has been logged.

[Oliver]

Right after installation? Or have you already set up some controllers or views?

[fmgujju]

I have installed and then setup controllers and views as per your post. I then created same pages with template that you have in you screenshot.

I have also corrected your code which was giving me error as follows:

public method function init()

parent::init(); (here one colon was missing)

Removed ... part.

I really like that I can use MVCish style in PW so if it works then I am all for it.

[Oliver]

I’ll try to reproduce it. Thanks for the corrections.

[Oliver]

@fmgujju: I guess I solved it. It was a minor error when passing method calls through my PvcPageProxy class. Grab the latest version from github and give it another try. Thanks for testing. There has been another error in my examples above: In products’ action template for index you have to add ->url at the end of the PW API call within the src attribute of the img tag to make it show the images.

[Soma]

Thanks Oliver for sharing, just I can't really try it out for various reasons.

I'm really digging people share their "MVC" approaches, but with this one more, it would be around 5 different ones now around. I'm not sure what to think about the impact on PW new and old users, support etc as it will split and create burdens for one to help someone using x-mvc approach. I have nothing against many ways to setup PW projects and while that's a strength it may even more is a weakness at the same time with its consequences. 

Really not against you and your approach, it just turns out by chance that I write this here. I'm not sure its worth of discussion.

Wouldn't it be better to settle on one "MVC" ish setup that PW maybe even supports, it could help to keep focus on it and maybe even have official docs for it. Often it doesn't help telling a dev hey look there's this this and this but you can also use this and this, but that is not for PW 2.5 while that is only for php 5.5 and the other you can't use if you use multisite and those are not multilanguageable. Hard for me to explain well but I think one get the idea where I'm heading.

[Oliver]

I absolutely get your point, Soma. I’ve always been a trial-and-error kind of coder, so I tried a lot, built a lot of stuff the way I thought was right. I hated how bad my code was structured and how hard it was to maintain. So I experimented with ways to separate things, tried approaches like your “delegate” one but didn’t really arrive at a point of happiness.

As I said I have been experimenting with other languages and frameworks like Ember, Rails etc. and I really fell in love with the burden of defining a meaningful and comprehensible structure being taken off me. Of course, the thing that brought me to PW was its freedom. But for me as a designer it was especially the freedom of how to build templates (as data containers) and how to present them easiy with PWs API at hand in your template files. But as soon as you want your PW site to do more than render web pages it (at least in my semi-semi-pro-dev experience) gets messy pretty fast when you try to wire things up to make a page do more than one thing.

So I really think it’s justifiable to use PWs modular base to build a MVCish layer upon it. Especially when you think of the fact that native page rendering has been a module itself from the start. Of course it’s not ideal to have a dozen of concepts around. I’ve kept an eye on earlier modules/concepts going in a similar direction but they mostly just dealt with a certain part of my issue. So I started experimenting (again) to create kind of a proof of concept and I wanted to share this with the community. 

If there is a real MVCish approach that is/will be supported by PW Core Team I’d be more than happy to support it. Did I miss something here?

[fmgujju]

@fmgujju: I guess I solved it. It was a minor error when passing method calls through my PvcPageProxy class. Grab the latest version from github and give it another try. Thanks for testing. There has been another error in my examples above: In products’ action template for index you have to add ->url at the end of the PW API call within the src attribute of the img tag to make it show the images.

Thanks Oliver! It's working now after grabbing your latest code.

[Oliver]

Great! Let me know if you got other issues or feedback.

[justb3a]

That sounds great, I will use and test it in my next Processwire project for sure! Looking forward for the PvcRendererTwig 

[Beluga]

ircmaxell has been writing about the problems with MVC in the context of PHP recently.

He seems to have a proposal cooking, so be sure to follow his blog