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Page Classes - Diving into one of ProcessWire's best features


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Page classes are an outstanding feature of ProcessWire and probably ranks among my favorites overall (and that's really saying something with ProcessWire). I don't remember how I lived without them, well I do, but I don't like to think about it.

I wrote a response to a question asking how ProcessWire can help transition from procedural code to OOP and in the process (pardon the pun) of answering, I realized how much I've come to use, if not outright rely on, page classes in every project. I wanted to compile a few more thoughts and examples here because there may be devs who are finding this feature for the first time, and besides, why not go down the rabbit hole?

Page classes have been around since ProcessWire 3.0.152 and if you're not familiar this will all make a lot more sense if you do a quick read of the feature announcement by Ryan here because this post assumes familiarity. We're also going to pick up the pace between the examples below compared to my comment in the link above.

Here are a few goals that I have that page classes put solutions for within reach. You may have some of your own and I'd love to hear about those as well.

  • Keep templates clean by restricting logic to flow operations- if statements and loops.
  • Work with data in context, accessing data and fields closer to their source.
  • Create "universal" methods available in every template, but also have scoped methods per-template
  • Increase the scalability of a project, growth with limited increases in complexity.
  • Stay DRY
  • Embrace and extend the power of OOP in ProcessWire's DNA

This seems like quite a list for one feature to handle, but rest assured, this is an example of how much power comes with using page classes. I'll continue and build on the blog example from my linked response above, and you can "follow along" with the Blog module since the templates mentioned are present out of the box. Some of the examples below are taken from production code, but please excuse any errors that I may have introduced by accident and I'm happy to update this post with corrections. Some of these things can be done other ways but they're just to illustrate, replace with your ideas and think of times that this would be useful.

First up, what are some features and behaviors that everyone needs on every project? What are some universal methods that would be great to have everywhere? Let's start out by creating a "base" page class called DefaultPage. Going forward, page classes will extend this class instead of Page and benefit from having access to universal methods and properties.

EDIT: I initially wrote this using BasePage rather than DefaultPage for this class name as described by the custom page class writeup by Ryan in the article above. I've changed this to now use the correct DefaultPage class name.

<?php namespace ProcessWire;

// /site/classes/DefaultPage.php

class DefaultPage extends Page {

  /**
   * Returns all top level pages for the main navigation.
   */
  public function navigationPages(): PageArray {
    $pages = wire('pages');
    $selector = 'parent=1';
    $excludedIds = $pages->get('template=website_settings')
      ->nav_main_excluded_pages
      ->explode('id');

    // Check for excluded pages from nav defined in the "Website Settings" page
    count($excludedIds) && $selector .= ',id!=' . implode('|', $excludedIds);

    $homePage = $pages->get('id=1');
    $topLevelPages = $pages->find($selector);
    $topLevelPages->prepend($homePage);

    return $topLevelPages;
  }

}

All your base page are belong to us. Right off the bat we've managed to pull complex logic usually in templates and kept our markup clean. This isn't for DRY, it's to store logic out of templates.  This simple example only illustrates working with a top level page nav. We can start to appreciate the simplicity when considering how much more the navigation may call for in the future. A navigationChildren method that also accounts for excluded pages is a prime example. In our markup:

<!-- /site/templates/components/site_nav.php -->
<nav>
  <ul>
    <?php foreach ($page->navigationPages() as $navPage): ?>
      <li>
        <a href="<?= $navPage->url; ?>"><?= $navPage->title; ?></a>
      </li>
    <?php endforeach ?>
  </ul>
</nav>

Next up, our settings page has newsletter signup fields where users can copy/paste form embed code from Mailchimp.

  • Our website has a "settings" page where global values and fields can be edited and maintained
  • There are multiple textarea fields on the settings page that can each contain a different mailchimp embed code
  • There is an embed select field that can be added to templates. The values are textarea field names so an embed can be chosen by the user.
  • An embed select field has been added to the settings page which allows for choosing a default embed code if one isn't selected when editing a page
  • Embedded forms should be available anywhere on any template
<?php namespace ProcessWire;

// /site/classes/DefaultPage.php

class DefaultPage extends Page {

  // ...Other DefaultPage methods

  /**
   * Renders either a selected form embed, fallback to default selected form
   */
  public function renderEmailSignup(): ?string {
    $settingsPage = wire('pages')->get('website_settings');
    
    $embedField = $this->signup_embed_select ?: $settingsPage->default_email_embed;

    return $settingsPage->$embedField;
  }

}

Excellent. We've got some solid logic that otherwise wouldn't have a great home to live in without page classes. We can also modify this one method if there are additional options or complexity added to the admin pages in the future. Wherever we use renderEmailSignup, the return value will be either the selected or default form embed code.

Let's create a folder called "components" in our templates directory that will hold standalone reusable markup we can use wherever needed, here's our newsletter signup component:

 <!-- /site/templates/components/newsletter_signup.php -->
<div class="newsletter-signup">
  <?= $page->renderEmailSignup(); ?>
</div>

Great! We've kept logic out of our code. We can render the field, and we can account for an empty value with a fallback. Unfortunately this is pretty limited in that it only handles a specific field, and it's implementation isn't as flexible as a component should be.

We can fix that, and here are some new requirements to boot:

  • Some templates may have multiple embed select fields which may or may not have a value
  • Each embed select field is now paired up with a text field to add some content that appears with each form embed, think "Sign up for our newsletter today!"
  • We want to render our mailchimp form embeds using the same component file, but handle different fields

Sounds like a tall order, but it's a challenge easily overcome with page classes. We're going to introduce a new method called renderComponent that will be global, reusable, and very flexible. We're also going to make use of another very great ProcessWire feature to do it. Back to our DefaultPage class:

<?php namespace ProcessWire;

// /site/classes/DefaultPage.php

class DefaultPage extends Page {

  // ...Other DefaultPage methods

  /**
   * Renders a file located in /site/templates/components/ with optional variables
   */
  final public function renderComponent(string $file, ...$variables): string {
    $componentsPath = wire('config')->paths->templates . 'components/';

    return wire('files')->render($file, $variables, ['defaultPath' => $componentsPath]);
  }

  /**
   * Renders either a selected form embed, fallback to default selected form
   */
  public function renderEmailSignup(?string $embedSelectField = null): ?string {
    $settingsPage = wire('pages')->get('website_settings');
    
    $embedField = $this->$embedSelectField ?: $settingsPage->default_email_embed;

    return $settingsPage->$embedField;
  }

}

We've done a couple of things here. We've updated renderEmailSignup to accept a field name, so now we're flexible on exactly which field select we'd like to check for a value on before falling back to default. We've also created a renderComponent method that is going to be super useful throughout the rest of our ProcessWire application.

Our renderComponent receives a file name located in the components directory and any number of named parameters. You could change the $variables parameter to an array if you'd like, but I'm a big fan of the great features we have now in PHP 8+. Here's our refactored component file:

 <!-- /site/templates/components/newsletter_signup.php -->
 <?php if ($embedField): ?>

  <div class="newsletter-signup">
    <?php if ($text): ?>
      <h2><?= $text; ?></h2>
    <?php endif ?>

    <?= $page->renderEmailSignup($embedField); ?>
  </div>
 
 <?php endif ?>

And let's hop over to our (abbreviated) home page template:


<body>
  <!-- ...Sections full of great content -->

  <section class="signup-call-to-action">
    <?= $page->renderComponent('newsletter_signup.php', embedField: $page->embed_select, text: $page->text_1); ?>
  </section>

  <!-- ...Your awesome template design -->

  <section class="page-end-call-to-action">
    <?= $page->renderComponent('newsletter_signup.php', embedField: $page->embed_select_2, text: $page->text_2); ?>
  </section>

  <!-- Your footer here -->
</body>


I don't know about you, but this is looking really good to me. The number of things we've accomplished while having written so little code is remarkable:

  • Because we used wire('files')->render(), the entire ProcessWire API is available within the component, so now our renderEmailSignup method is too.
  • The variadic function parameters (or array if preferred) let us pass an arbitrary number of variables to any component file, unrestricted future flexibility
  • Variables are scoped to each component! There's no reference to template fields in our component that could break if changes are made
  • No more PHP includes, we don't have to juggle paths or constantly repeat them in our code, nor rely on declaring variables before including a file.
  • ProcessWire will throw an exception if we try to render a file that does not exist which makes locating issues very easy
  • We'll also see an exception if we try to reference a variable in our component that wasn't passed which can also help troubleshooting.
  • Notice that the renderComponent is final. We want that behavior to remain consistent everywhere we use it and not overwritten either intentionally or by accident on our inheriting page classes. We want to eliminate any confusion between templates by knowing it will always do the same thing the same way.

We can explore other uses too, perhaps a renderPartial for files in /site/templates/partials where we store files like site_header.php.  As mentioned above however, if a variable is expected in the rendered file but not included in our render method, we'll see an exception. Let's use site_header.php as an example because we're sure to run into situations where variables may or may not exist:

<?php namespace ProcessWire;
// /site/templates/partials/site_header.php
?>
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title><?= $page->title; ?></title>
  <meta name="description" content="<?= $metaDescription ?? null; ?>">
  <?php if ($includeAnalytics ?? true): ?>
    <script>
      // All that Google Analytics jazz
    </script>
  <?php endif ?>
</head>
<body class="<?= $bodyClasses ?? null; ?>">
  <header>
    <?= $page->renderComponent('site_nav.php', includeEmailButton: true); ?>
  </header>

Problem: solved. By using nullsafe ?? operators, we can call $page->renderPartial('site_header', description: 'The ultimate Spice Girls fan page.'); and never get errors for variables that may not be included when calling renderComponent, such as includeAnalytics, which now also has a default value of 'true'. Nice.

We haven't even gotten to our actual page classes yet... Our templates are about to receive superpowers.

Let's take our blog to the next level. In my comment on the other thread, I created a specific example of adding a readTime method to our blog posts, let's go one level higher to our blog.php template. We'll populate some methods up front and then talk about what we've done:

<?php namespace ProcessWire;

// /site/classes/BlogPage.php

class BlogPage extends DefaultPage {

  /**
   * Get latest blog posts, optionally with/without pinned post, optionally in blog category
   */
  public function latestPosts(
    int $limit = 3,
    bool $includePinnedPost = true,
    ?int $categoryId = null
  ): PageArray {
    $selector = 'template=blog-post';

    if ($categoryId) {
      $selector .= ",blog_category={$categoryId}";
    }

    $posts = wire('pages')->get($selector);

    if ($includePinnedPost) {
      $pinnedPost = $this->getPinnedPost();

      if ($pinnedPost) {
        $posts->remove($pinnedPost);
        $posts->prepend($pinnedPost);
      }
    }

    return $posts->slice(0, $limit);
  }

  /**
   * Gets an optional pinned post if set/chosen
   * pin_blog_post A checkbox to indicate whether a post should be pinned
   * pinned_post   A InputfieldPage field to choose a blog post
   */
  public function getPinnedPost(): ?Page {
    if (!$this->pin_blog_post) {
      return null;
    }

    return wire('pages')->get($this->pinned_post);
  }

}

On our main blog page a user has the ability to choose whether a blog post is "pinned". A pinned post will always remain the first post anywhere a list of posts is needed, something like a big company announcement that the client wants to keep visible. These two methods alone have given us awesome abilities.

For our main blog page, when someone visits our blog page, the most recent or pinned post is presented at the top, followed by the next two most recent posts, followed by two rows of 3 posts, for a total of 9. Let's assume that we've already created the BlogPostPage.php with the readTime method from my previous example. Here's our blog.php template

<?php namespace ProcessWire;

echo $page->renderPartial(
  'site_header.php',
  bodyClasses: 'blog-page',
  metaDescription: $page->blog_description
);

$posts = $page->latestPosts(9);
$firstPost = $blogPosts->first();
?>

<section class="main-post">
  <article>
  	<img src="<?= $firstPost->blog_image->url; ?>" alt="<?= $firstPost->blog_image->description; ?>">
  	<h1><?= $firstPost->title; ?></h1>
  	<?= $firstPost->summary; ?>
  	<span><?= $firstPost->readTime(); ?></span>
  	<a href="<?= $firstPost->url; ?>">Read More</a>
  </article>
</section>

<section class="recent-Posts">
  <?= $page->renderComponent('blog_preview_card.php', blogPost: $posts->get(1)); ?>
  <?= $page->renderComponent('blog_preview_card.php', blogPost: $posts->get(2)); ?>
</section>

<section class="past-posts">
  
  <?php foreach ($posts->slice(3, 6) as $post): ?>
    <?= $page->renderComponent('blog-preview_card.php', blogPost: $post); ?>    
  <?php endforeach ?>
  
</section>

<?= $page->renderPartial('site_footer.php'); ?>

So first off, we've really started to use our renderComponents method and component files. We also implemented a renderPartial as speculated upon above. Each does a similar thing, but having separate methods makes everything clear, handles paths, but still has a similar interface when calling them.

A big thing to notice here is that at no point have we added any markup to our page classes, and no business logic to our templates. If we need to find anything, we know where to look just by glancing at the template. Ultimate maintainability.

Here's our blog_preview_card.php component:

<?php namespace ProcessWire; ?>

<!-- /site/templates/components/blog_preview_card.php -->

<article class="blog-preview-card card">
  <img src="<?= $blogPost->blog_image->url; ?>" alt="<?= $blogPost->blog_image->description; ?>">
  
  <h2><?= $blogPost->title; ?></h2>
  
  <div class="blog-summary">
  	<?= $blogPost->blog_summary; ?>
  </div>
  
  <span class="blog-read-time"><?= $blogPost->readTime(); ?></span>
  
  <a href="<?= $blogPost->url; ?>">Read More</a>
</article>

I am liking how well this is working out! Page classes have done a ton of heavy lifting here:

  • We're using our renderComponent method to it's maximum potential and it's payed off in spades
  • Our template couldn't be cleaner or more easily maintainable
  • BlogPostPage.php has taken care of all of our needs as far as delivering the PageArray of posts and all our template does is output the data as needed
  • Our "card" component will render the same thing everywhere and we can update how that looks globally with changes to one file

If you don't think this can get more awesome, or think this post is already too long, I have bad news for you and you should stop reading now.

Still here? Let's create a BlogPostPage class and add a method:

<?php namespace ProcessWire;

// /site/classes/BlogPostPage.php

class BlogPostPage extends DefaultPage {

  // ... Other page methods, like readTime()
 
  public function relatedPosts(int $limit = 3): PageArray {
    return wire('pages')->get('template=blog')->latestPosts(
      limit: $limit,
      includePinnedPost: false,
      categoryId: $this->blog_category?->id
    );
  }
}

The BlogPage::latestPosts method is really flexing it's muscle here. We've used it in two different places for different purposes but requesting similar data, blog posts. If you noticed, we're also specifying a category for this blog since we have a page select field that references a blog category. That was a parameter that we included back in our BlogPage::latestPosts() method.

So, blog posts have a "You might also be interested in..." section with posts in the same category as the that one that a visitor has just read. With page classes this couldn't be easier to add, so let's use the relatedPosts method we just created in BlogPostPage.php in our blog-post.php template:

<?php namespace ProcessWire;

// /site/templates/blog-post.php

echo $page->renderPartial(
  'site_header.php',
  bodyClasses: 'blog-post',
  metaDescription: $sanitizer->truncate($page->blog_summary, 160)
);
?>

<!-- The page hero, blog content, stuff, etc. -->

<section class="related-posts">
  
  <?php foreach ($page->relatedPosts() as $post): ?>
    <?= $page->renderComponent('blog_preview_card.php', blogPost: $post); ?>
  <?php endforeach ?>
  
</section>

<?= $page->renderPartial('site_footer.php'); ?>

We've just added a related posts feature in *checks stopwatch* seconds. This project is going so fast that you can already hear the crack of the cold beer after a job well done.

One more example, and I'll let you decide if this is too much, or feels just right. We want a blog feed on our home page. So before we go to the home.php template, let's do what we do (surprise, it's a page class):

<?php namespace ProcessWire;

// /site/classes/HomePage.php

class HomePage extends DefaultPage {

  // Other HomePage methods...
 
  public function blogFeed(int $limit = 3): PageArray {
    return wire('pages')->get('template=blog')->latestPosts(limit: $limit);
  }
 
}

At first glance, this might seem like a bit much. Why create a method in our page class that is so short and simple? We could just call $pages->get('template=blog')->latestPosts(3) inside our template and get away with it just fine. Here's why I think it's worth creating a dedicated page class method:

  • This creates yet another example of predictability between templates
  • It promotes thie philosophy I like of page classes talking to page classes
  • It's likely that we'll have other more complex methods in the HomePage class, keeping them together feels right and helps with uniformity- we always know where to look when seeing custom methods
  • If we need to make a change to the BlogPage::latestPosts() method that affect how other page classes call that method, we don't have to root around in our templates to make any changes.
  • It's pretty nice to see that thus far we have only ever referenced the $page object in our templates! There aren't any calls to $pages because our template is really about doing one thing- rendering the current page without caring about other pages. That's not to say that we can't, or shouldn't, use other ProcessWire objects in our templates, but it's still impressive how much we've been able to scope the data that we're working with in each template.

I truly love the page classes feature in ProcessWire and even though this is a deeper dive than my other post, this really is still just scratching the surface because we can imagine having more complex behavior and other benefits. Here are some from my experience:

  • Handling AJAX calls to the same page. Choosing how and what type of content is returned when the page is loaded is really nice. This can be done with hooks, but I really like page classes handling things like this in-context.
  • Working with custom sessions between one or more pages. Creating a trait that shares session behavior between page classes is a great way to extend functionality while keeping it scoped.
  • Adding external API calls and whatever complexity that may entail
  • Provides the ability to add significant complexity to our templates in the admin yet little to no additional complexity in template files. The basic "pinned post" and form embed features are just the start
  • As you can imagine, this makes replicating code you use often between projects trivial
  • Page classes provide a home for logic that otherwise would be stuck in a template, or relegated to a messy functions.php file. No more functions.php ever.
  • We met every single goal I listed here at the beginning
  • Every single template thus far only uses if statements and loops
  • DefaultPage could have a "bootApplication" method if needed that does things for every page and is called in ready.php. This is also a great way to create a "bootable" method in all of your page classes where bootApplication could call a bootPage method in your page classes if it exists.

Thanks for coming to my TED talk. Hope you find this useful! If you have any questions, corrections, use cases, or things to add, the comments below are open and I'd love to hear them!

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7 hours ago, zilli said:

Wow, this is so nice. Thank you very much!

Very happy to hear you enjoyed it!.

7 hours ago, zilli said:

Have you considered writing a beginner's course on PHP OOP using ProcessWire as the main tool?

Writing a course on anything hasn't ever crossed my mind haha.

I just put this together to share a great ProcessWire feature that has really boosted my workflow and thought maybe sharing some examples might be useful to others. I hadn't thought about this post as a walkthrough on OOP specifically, but I did want to be descriptive in a way that would be useful to as many people as possible- whether you are familiar with OOP or not, and without any assumptions. All said, I'm happy to try and answer questions if it would help anyone ?

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Yeah custom page classes are absolutely essential to everything I put together.

It's really nice to be able to populate interfaces for different page types this way - e.g. I have a jsonld method I attach to various page classes that allow me to segregate the structured data and custom tailor it for each class - but in various templates I can simple $page->jsonld() and not think about the schema more than once for each page class. I already know the right fields for a given page type will go in the right spots in the schema output.

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On 6/26/2024 at 7:08 PM, Alpina said:

As a beginner, I would love to learn how you usually set up a simple institutional website.

I'd be happy to provide something like that. I'm really short on free time right now but I may be able to adapt a real life example once I get enough done on one of my projects. That way I can avoid double work and have a good example. Will keep it in mind and bring that info back here as a demo repository when I can do it right.

On 6/29/2024 at 3:53 PM, gornycreative said:

I have a jsonld method I attach to various page classes that allow me to segregate the structured data and custom tailor it for each class - but in various templates I can simple $page->jsonld() and not think about the schema more than once for each page class

I've implemented the exact same method on sites before and that's a great example. I like to create a jsonld() method which returns null in my BasePage class that exists specifically to be overwritten by inheriting pages. That way I can call $page->jsonld() in a partial like site_header.php without any logic, it renders something or it doesn't.

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  • 2 weeks later...

What a great writeup! Thank you for putting your time into this. It could be part of the official docs for page classes.

I would be interested in your reasoning behind naming the base class BasePage. In the docs that you linked, Ryan suggests DefaultPage. In https://github.com/processwire/processwire/blob/3cc76cc886a49313b4bfb9a1a904bd88d11b7cb7/wire/config.php#L202 it says:
 

Quote

If you create a file named /site/classes/DefaultPage.php with a DefaultPage class within
 it (that extends Page), then it will be used for all pages that would otherwise use the 
 `Page` class.

So are you using BasePage to not have every Page be based automatically on DefaultPage?

I'm asking this, because I am using the DefaultPage class quite a lot and in some cases it caused some minor unexpected behaviours because the class is used for every Page.

On 6/23/2024 at 2:50 AM, FireWire said:

page classes will extend this class instead of Page and benefit from having access to universal methods and properties

Would love to see how you implement properties in your base page class. Specifically how and where do you assign them?

I utilize the loaded() method to assign those properties and found that it added lots of overhead because loaded() is called for every page that is loaded in a PW lifecycle when using it on the DefaultPage class. And that seemed a bit expensive to me, especially if construction of some properties requires more complex and expensive logic.

Here's an example on how I implement custom properties on runtime

class DefaultPage extends Page
{
    // trait that provides methods for responsive images
    use ResponsiveImages;

    // define statuses that should be excluded from loadingcustom properties
    const excludeStatuses = array(
        Page::statusTrash,
        Page::statusUnpublished,
        Page::statusDraft,
    );

    public $introTitle;
    public $introText;

    // set custom properties in loaded
    public function loaded()
    {
        // load custom properties only for allowed statuses
        if (!empty(array_intersect(array_keys($this->status(true)), self::excludeStatuses))) return;

        $this->set('introTitle', $this->text);
        $this->set('introText', nl2br($this->textarea));
    }

}

I found that loaded() is called for every page regardless of their status. So I prevent loaded() from assigning properties for some statuses where the properties are not needed.

Why I want to have custom properties in the first place? Almost all fields in my PW installations get very generic names like text, textarea, rte, image, text2 etc. I am using those fields in different templates for different purposes. Custom properties are a nice way to access those generic fields in a more meaningful manner and have them available in intellisense.

 

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1 hour ago, gebeer said:

I would be interested in your reasoning behind naming the base class BasePage

Well, funny story, I have no reasoning. I just misremembered between reading that and hacking out this post. Jumping between projects in and outside of ProcessWire didn't help haha. I've used DefaultPage in the past, it was just an oversight this time around. Ryan's is of course the correct way. I generally always have a custom page class for each of my templates so I've never had an issue where DefaultPage was loaded on it's own. Appreciate you mentioning it, I've updated the post to use DefaultPage.

2 hours ago, gebeer said:

I'm asking this, because I am using the DefaultPage class quite a lot and in some cases it caused some minor unexpected behaviours because the class is used for every Page.

My first reaction is that unexpected behaviors may indicate that there may be too much abstraction. My DefaultPage classes have traditionally been lightweight and stick to only containing what can be reliably counted on as valuable across all pages. One of the criticisms of OOP is that classes and inheritance can make for brittle code so it's something that I try to be mindful of. It may also be good to try an keep anything that executes automatically or hooks into the Page lifecycle to a minimum (maybe none at all) in DefaultPage since it spans the entire application.

1 hour ago, gebeer said:

Almost all fields in my PW installations get very generic names like text, textarea, rte, image, text2 etc. I am using those fields in different templates for different purposes. Custom properties are a nice way to access those generic fields in a more meaningful manner and have them available in intellisense.

I use names like these myself for the same reason. Really helps keep a sane number of fields and reduce redundancy.

I haven't taken this approach to reassigning values to properties like this but it's an interesting idea. I reviewed the code for the Page class and there is a good amount of logic in Page::set() that can be useful when working with values but may not be needed within the context of a page class. At first blush though I would just assign the value of the field to an instance variable directly rather than call Page::set() because at time of authorship- you know what field you'll be working with, it's data type, and intended usage within the context of that template/page.

<?php

public $introTitle;
public $introText;

// set custom properties in loaded
public function loaded()
{
  // load custom properties only for allowed statuses
  if (!empty(array_intersect(array_keys($this->status(true)), self::excludeStatuses))) return;

  $this->introTitle = $this->text;
  $this->introText = nl2br($this->textarea);
}

I may be missing the added value of using Page::set() in your use case though.

My other thought though is that if these fields have consistent and wide enough usage through all templates, enough to reassign them to alternate property names, they might be a candidate for dedicated fields rather than repurposing generalized fields. Both introTitle and introText seem like they have wide enough usage, so I would create those fields and skip any extra logic needed here in DefaultPage.

I actually haven't set a lot of instance variables in page classes. I've focused on methods that can abstract logic out of templates, or perform computationally expensive operations only on demand. Here's a DefaultPage from a production site:

<?php namespace ProcessWire;

use Ramsey\Uuid\Uuid as Uuid;
use \DateTime;

class DefaultPage extends Page
{
  /**
   * Paths for rendering methods
   */
  const COMPONENTS_PATH = '/../templates/components/';

  const FORMS_PATH = '/../templates/components/forms/';

  const PARTIALS_PATH = '/../templates/partials/';

  const SVG_PATH = '/../templates/img/svg/';

  /**
   * Stub method that may be overridded by inheriting classes where needed
   */
  public function renderStructuredData(): ?string
  {
    return null;
  }

  /**
   * Outputs full path and filename for CSS files
   */
  public function css(string $file): string
  {
    return wire('config')->urls->templates . "dist/styles/{$file}";
  }

  /**
   * Outputs full path and filename for JavaScript files
   */
  public function js(string $file): string
  {
    return wire('config')->urls->templates . "dist/scripts/{$file}";
  }

  /**
   * Returns contents of an SVG file with unique IDs for title/description attributes for accessibility
   */
  final public function renderSvg(string $file, array $variables = []): string
  {
    $variables = array_merge($variables, [
      '{ARIA_TITLE_ID}' => Uuid::uuid4()->toString(),
      '{ARIA_DESC_ID}' => Uuid::uuid4()->toString(),
      '{CLASSES}' => $variables['classes'] ?? null,
    ]);

    return strtr(file_get_contents(__DIR__ . self::SVG_PATH . $file), $variables);
  }

  /**
   * Renders a file in /templates/partials/
   */
  final public function renderPartial(string $file, array $variables = []): string
  {
    return wire('files')->render($file, $variables, [
      'defaultPath' => __DIR__ . self::PARTIALS_PATH
    ]);
  }

  /**
   * Renders file located in templates/components/
   */
  final public function renderComponent(string $file, array $variables = []): string
  {
    return wire('files')->render($file, $variables, [
      'defaultPath' => __DIR__ . self::COMPONENTS_PATH
    ]);
  }

  /**
   * Renders a form
   */
  final public function renderForm(string $file, array $variables = []): string
  {
    return wire('files')->render($file, $variables, [
      'defaultPath' => __DIR__ . self::FORMS_PATH
    ]);
  }

  /**
   * Gets the time period of the day based on the hour
   */
  final public function getPeriodOfDay(): string
  {
    $hour = (new DateTime())->format('H');

    switch (true) {
      case $hour < 12:
        return 'morning';
      case $hour >= 12 && $hour <= 17:
        return 'afternoon';
      default:
        return 'evening';
    }
  }

  /**
   * Returns all top level pages for the main navigation
   */
  final public function topLevelPages(): PageArray
  {
    $pages = wire('pages');
    $selector = 'parent=1';
    $excludedIds = $pages->get('template=admin_website_settings')
                         ->nav_main_excluded_pages
                         ->explode('id');

    // Check for excluded pages from nav defined in the "Website Settings" page
    count($excludedIds) && $selector .= ',id!=' . implode('|', $excludedIds);

    $homePage = $pages->get(1);
    $topLevelPages = $pages->find($selector);
    $topLevelPages->prepend($homePage);

    return $topLevelPages;
  }
}

All of the other magic goes into traits or inheriting page classes. My soft guidelines when it comes to code organization is:

  • Save abstraction until something is repeated 3 times, consistency should be maintained, or complexity warrant it for the sake of the surrounding code.
  • Abstract to a trait or enum that can be selectively used where needed.
  • Consider abstracting to a parent class last, there has to be a case for why it should be shared between all classes because it's more than ubiquity, it comes down to rock solid shared behavior and purpose
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24 minutes ago, FireWire said:

My first reaction is that unexpected behaviors may indicate that there may be too much abstraction. My DefaultPage classes have traditionally been lightweight and stick to only containing what can be reliably counted on as valuable across all pages. One of the criticisms of OOP is that classes and inheritance can make for brittle code so it's something that I try to be mindful of. It may also be good to try an keep anything that executes automatically or hooks into the Page lifecycle to a minimum (maybe none at all) in DefaultPage since it spans the entire application.

This was most likely what caused that behaviour. So yeah, we have to be very mindful there. Guess I needed to learn that the hard way 🙂 Great suggestions here.

And thanks for your thoughts on properties in page classes and the very well structured example you give.

29 minutes ago, FireWire said:

I actually haven't set a lot of instance variables in page classes.

There might be a good reason to avoid them, since they add overhead to Page loading. And I haven't found other methods like init or ready that are suitable for attaching those properties. Since my main goal with them was to have sensibly named props that intellisense can discover, I might as well stick with methods.

After having worked for some time with implementing those props via the loaded() method in the past, nowadays I avoid them for the reasons mentioned.

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How to initialize a "custom page" object has also been discussed here before: https://processwire.com/talk/topic/25342-custom-classes-for-page-objects-the-discussion/

and is also discussed in this request at Github: https://github.com/processwire/processwire-requests/issues/456

I'd love to see an "officially supported and recommended way" of doing this.

 

 

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50 minutes ago, szabesz said:

How to initialize a "custom page" object has also been discussed here before: https://processwire.com/talk/topic/25342-custom-classes-for-page-objects-the-discussion/

Actually that post is where I got to learn that we can use loaded() for initialisation. It is great that you discussed this in such detail there, especially the drawbacks.

I thought, since the OP seems to have a lot of expertise in using page classes, I'd ask him if he had found a more elegant way than using loaded(). And putting everything together that I have learned about page classes, I will avoid initialisation of props using loaded() with DefaultPage going on from here 🙂

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I use a mixture of calls to run various initializing code, depending on what to initialize, e.g., copied from a Product page's custom class:

/*
 * Called when the page is requested on the frontend.
 * Called from _init.php via include_once(config()->paths->templates . 'path/to/this/_init_once.php');
 * so that it only runs once per request:
 * page()->requested();
 */
public function requested() {
    $this->request_ws = "\ProcessWire\RqtProduct";
    parent::requested();
}

/*
 * When initialization of object properties is required right from the beginning.
 */
function __construct(Template $tpl = null) {
    parent::__construct($tpl);
    $this->factsAy = new Arrayy([]);
}

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

    // Either building a structured array of all product data and caching it in a variable or reading that from memory.
    if (empty($this->facts)) {
        $this->encodeFacts();
    } else {
        $this->factsAy = Arrayy::createFromJson($this->facts);
    }
}

/**
 * Product page specific hooks. This method is called from site/init.php from my custom loop 
 * that runs for each frontend template based page.
 * if (in_array($templateName, config()->noneFrontendTemplates)) {
    * if ($templateName === "user") call_user_func_array("{$namespace}{$className}::initiate", []); // UserPage needs special treatment.
    * continue;
 * }
 * if (class_exists($namespace . $className)) call_user_func_array("{$namespace}{$className}::initiate", []); // Page classes register hooks in their initiate() method this way.
 */
public static function initiate() {
    parent::initiate();

    wire()->addHookBefore("Pages::saveReady(template=product)", function ($event) {

... more hooks go here ....

 

Edited by szabesz
Edit: I extended the last comment with an extra line.
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3 hours ago, gebeer said:

I'd ask him if he had found a more elegant way than using loaded().

I meant to mention that I didn't know about that method before your comment. Now that I know about it though I'll probably end up using it. So thank you for the tip!

There was one instance where it may have come in handy. I created a PageClass method that analyzes the current page request to determine if it was an AJAX request for a specific purpose, but decided to just call $page->whateverMethdName() at the top of the template before anything rendered. The loaded() method is the way I'll go with that next time.

3 hours ago, gebeer said:

since the OP seems to have a lot of expertise in using page classes

I learned something new today 😎

3 hours ago, szabesz said:

I use a mixture of calls to run various initializing code

Bookmarking this. Keeping hooks closer to the location/context that makes sense is a good idea.

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1 hour ago, FireWire said:

Bookmarking this. Keeping hooks closer to the location/context that makes sense is a good idea.

As I know you are using RockMigrations / RockPageBuilder have you seen https://www.baumrock.com/en/processwire/modules/rockmigrations/docs/magicpages/ ?

It will let you define hooks in an init() or ready() method in your custom page class. There you can add hooks and RM will make sure it will only trigger init/ready once for each pageclass, which is one culprit when using loaded() as it will get triggered multiple times and potentially add hooks more often than once.

Also it has shortcuts for often needed hooks, so for example you can hook the backend page edit form like this:

  public function editFormContent($form) {
    $form->add([
      'type' => 'markup',
      'label' => 'foo',
      'value' => 'bar',
    ]);
  }

 

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