Paul M. Jones

To learn six subjects without remembering how they were learnt does nothing to ease the approach to a seventh; to have learnt and remembered the art of learning makes the approach to every subject an open door.

Source: The Lost Tools of Learning

Selling is a pure popularity contest. Awards are pure popularity contests. Once you get over that, the better your friends will do and the better you will do.

...

When you want to do something with the culture, post your memes, be funny, be quick witted. That’s all that matters in this internet era. If you want to see change, it starts there.

Source: How I Use Rhetoric To Sell Books | The Writings of Jon Del Arroz

From an email conversation with a reader:

Hi Paul,

I’ve been following your writing and examples about the ADR pattern for some time now. It’s taken me awhile to wrap my head around it but ADR has really added a lot of structure to my code and I’m thankful for your work!

One dilemma that I’ve been struggling with is how to organize emails that are sent out by my service classes. Currently my business logic dictates when to send an email and most of them contain html and text templates. It just feels wrong to include those email templates within the Domain. Do you have any recommendations? Any help you can provide would be greatly appreciated.

In a somewhat related question - Recently I’ve been organizing my “views” folders within the folders of their parents (Http, Mail). I think I based it on your ADR example on github. Do you still prefer this method or do you lean towards organizing within a “resources” folder?

My intuition is that you are right to keep the email templates out of the domain.

In a way, sending an email as part of a web request/response cycle is like sending two responses: the normal HTTP response, and the email response. With that in mind, it might make sense to think of the HTML + Text email templates as part of a presentation layer. Or, as a combination of infrastructure (the email-sending client) plus presentation (the templates). That would be how to think about the separation of concerns there.

Here’s an example of what that separation of concerns might look like in a package directory structure:

resources/
    templates/
        web/
            # web page templates
        email/
            message-1/
                message-1.html
                message-1.txt
            message-2/
                message-2.html
                message-2.txt
src/
    Domain/
        AppService/
            FooAppService.php
            BarAppService.php
        EmailInterface.php
        # ... other domain classes
    Infrastructure/
        DataSource/
            # ... mappers, tables, etc
        Emailer.php # implements Domain\EmailInterface
    Web/
        Foo/
            FooAction.php
            FooResponder.php
        Bar/
            BarAction.php
            BarResponder.php

The specifics of directory structure are not important, as long as you see that the Emailer class is separated from the Domain application services (or use cases, or whatever).

The Emailer class, for its part, might be a facade [1] that coordinates between a “real” emailer (e.g. Swiftmailer or PhpMailer) and a template class, to put together and then send the email. You could configure the Emailer class with the template location (resources/templates/email/*) and inject it into your application service (which depends on the EmailInterface).

Now, sending emails inline as part of the web request might be fine in a lower-traffic situation. But as volume scales up, this kind of separation will make it easy to extract all email-sending to a workers. Then the Emailer can queue emails to the workers instead of sending them inline with the web request; the email-sending can become the job of a queue worker, and the template work will go there instead.

As far as where to put templates for views:

The extended example ADR code on GitHub is a few years old at this point. I still think it’s a reasonable setup, especially for people transitioning out of pseudo-MVC toward ADR, but it might do well to receive an update (or some examples of variations).

I don’t prefer any particular method or structure on where to put templates. Sometimes it makes sense to keep templates near the things using them, sometimes it makes sense to collect them all one place. The needs of the system, and the prior experiences of the developer(s), will be the deciding factor as far as I’m concerned. I had PHP-PDS on the brain when I replied, so the pds/skeleton with its “resources” directory was at hand.

[1] A real facade, not a Laravel one. ;-)

Read the Reddit discussion about this post here.

The cold biological truth is that sex changes are impossible. Every single cell of the human body remains coded with one's birth gender for life. Intersex ambiguities can occur, but they are developmental anomalies that represent a tiny proportion of all human births.In a democracy, everyone, no matter how nonconformist or eccentric, should be free from harassment and abuse. But at the same time, no one deserves special rights, protections, or privileges on the basis of their eccentricity. The categories "trans-man" and "trans-woman" are highly accurate and deserving of respect. But like Germaine Greer and Sheila Jeffreys, I reject state-sponsored coercion to call someone a "woman" or a "man" simply on the basis of his or her subjective feeling about it. We may well take the path of good will and defer to courtesy on such occasions, but it is our choice alone.

A wide-ranging interview. Source: Camille Paglia: On Trump, Democrats, Transgenderism, and Islamist Terror | The Weekly Standard

The fact that the two deadliest attacks upon the U.K. in recent memory were at the hands of Islamic terrorists is not simply pub trivia. I mention it because when these apologists for Islam get bored of claiming that jihadists are incessantly and inexplicably lying about their religious motivations, they invariably engage in the crass exercise of throwing around skewed data in a desperate attempt to deemphasize the danger posed by Islamic terror. this is not due to some well-meaning concern for people worrying unnecessarily, or to ensure that counter terrorism strategy is accurately focused upon the most serious threat, it seems rather to be a tactical attempt to prioritize the protection of odious 7th century folklore over the welfare of real human beings.

In the not uncommon event of an Islamic lunatic slaughtering a crowd of innocent people, Americentric articles and tweets lying about the likelihood of this happening to you, instantaneously begin to surface, like gunk from the ocean floor after a depth charge detonation.

Source: No, You’re Not More Likely to Be Killed by a Right-Wing Extremist than an Islamic Terrorist – Areo Magazine

Christianity, it turned out, looked nothing like the caricature I once held. I found the story of Jacob wrestling with God especially compelling: God wants anything but the unthinking faith I had once assumed characterized Christianity. God wants us to wrestle with Him; to struggle through doubt and faith, sorrow and hope. Moreover, God wants broken people, not self-righteous ones. And salvation is not about us earning our way to some place in the clouds through good works. On the contrary; there is nothing we can do to reconcile ourselves to God. As a historian, this made profound sense to me. I was too aware of the cycles of poverty, violence and injustice in human history to think that some utopian design of our own, scientific or otherwise, might save us.

Source: How Oxford and Peter Singer drove me from atheism to Jesus - The Veritas Forum - The Veritas Forum

To explain how a scientist can be a Christian is actually quite simple. Science cannot and does not disprove the resurrection. Natural science describes the normal reproducible working of the world of nature. Indeed, the key meaning of “nature”, as Boyle emphasized, is “the normal course of events.” Miracles like the resurrection are inherently abnormal. It does not take modern science to tell us that humans don’t rise from the dead. People knew that perfectly well in the first century; just as they knew that the blind from birth don’t as adults regain their sight, or water doesn’t instantly turn into wine.

Source: Can a scientist believe in the resurrection? Three hypotheses. - The Veritas Forum - The Veritas Forum

A few months ago I had a great email conversation with a correspondent about how to handle business logic exceptions in his controller code. His message follows, lightly edited for brevity and clarity:

class FooController
{
    public function fooAction()
    {
        try {
            $this->service->doSomething('foo');
        } catch (ObjectNotFound $e) {
            throw new NotFoundHttpException('Not Found', $e);
        } catch (InvalidDataException $e) {
            throw new BadRequestHttpException('Invalid value', $e);
        } // ...
    }
}

If you find yourself in this situation, the first question to ask yourself is, “Why am I handling domain exceptions in my user interface code?” (Remember: Model-View-Controller and Action-Domain-Responder are user interface patterns; in this case, the user interface is composed of an HTTP request and response.) Domain exceptions should be handled by the domain logic in a domain-appropriate fashion.

My correspondent’s first intuition (using domain-level exceptions, not HTTP-specific ones) has the right spirit. However, instead of having the domain service throw exceptions for the user interface controller to catch and handle, I suggest that the service return a Domain Payload with domain-specific status reporting. Then the user interface can inspect the Domain Payload to determine how to respond. I expand on that approach in this post.

By way of example, instead of this in your controller …

class FooController
{
    public function fooAction()
    {
        try {
            $this->service->doSomething('foo');
        } catch (ObjectNotFound $e) {
            throw new NotFoundHttpException('Not Found', $e);
        } catch (InvalidDataException $e) {
            throw new BadRequestHttpException('Invalid value', $e);
        } // ...
    }
}

… try something more like this:

class FooController
{
    public function fooAction()
    {
        $payload = $this->service->doSomething('foo');
        switch ($payload->getStatus()) {
            case $payload::OBJECT_NOT_FOUND:
                throw new NotFoundHttpException($payload->getMessage());
            case $payload::INVALID_DATA:
                throw new BadRequestHttpException($payload->getMessage());
            // ...
        }
    }
}

(I am not a fan of using exceptions to manage flow control; I’d rather return a new Response object. However, I am trying to stick as closely to the original example as possible so that the differences are more easily examined.)

The idea here is to keep domain logic in the domain layer (in this case, a service). The service should validate the input, and if it fails, return a “not-valid” payload. The service should catch all exceptions, and return a payload that describes the kind of error that occurred. You can then refine your controller to examine the Domain Payload and handle it however you want.

Using a Domain Payload in this way is not a huge leap. Essentially you move from a try/catch block and exception classes, to a switch/case block and status constants. What’s important is that you are now handling domain-level exceptions in the domain and not in the user interface layer. You are also encapsulating the status information reported by the domain, so that you can pass the Domain Payload object around for something other than the controller to inspect and handle.

Encapsulation via Domain Payload opens the path to a more significant refactoring that will help reduce repetition of response-building logic across many controller actions. That next refactoring is to separate out the response-building work to a Responder, and use the Responder in the controller action to return a response. You can then pass the Domain Payload to the Responder for it to handle.

class FooController
{
    public function fooAction()
    {
        $payload = $this->service->doSomething('foo');
        return $this->responder->respond($payload);
    }
}

class FooResponder
{
    public function respond($payload)
    {
        switch ($payload->getStatus()) {
            case $payload::OBJECT_NOT_FOUND:
                throw new NotFoundHttpException('Not Found', $e);
            case $payload::INVALID_DATA:
                throw new BadRequestHttpException('Invalid value', $e);
            // ...
        }
    }
}

Once you do that, you’ll realize the majority of your response-building logic can go into a common or base Responder. Custom cases can then be be handled by controller- or format-specific Responders.

And then you’ll realize all your Action logic is all pretty much the same: collect input from the Request, pass that input to a Domain-layer service to get back a Domain Payload result, and pass that result to a Responder to get back a Response. At that point you’ll be able to get rid of controllers entirely, in favor of a single standardized action handler.

Read the Reddit discussion about this post here.

Circumstance has conspired to put Action Injection discussions in front of me multiple times in the past few days. Having seen the approach several times before, I have come to think that if Action Injection is the answer, you might be asking the wrong question. I find it to be a code smell, one that indicates the system needs refactoring or reorganizing.

Action Injection …

As far as I can tell, the term “Action Injection” originates with Alex Meyer-Gleaves in a 2010 article on ASP.NET MVC development. He summarizes Action Injection in this way:

Your [controller class] constructor is provided the dependencies [by the DI container] that are shared by all actions in your controller, and each individual action [method] can request any additional dependencies that it needs.

To expand on that, let’s say you have a controller class with several action methods in it. You realize after a while that the different action methods have slightly different dependencies. For example, some of the methods need a logger, while others need a template system, or access to the router. But you don’t want to pollute the controller class constructor with these method-specific dependencies, since those dependencies will be used only if that particular action method gets invoked.

With Action Injection, when you pull the controller from your dependency injection container and call a particular action method, the DI container will automatically pass the right dependencies for the method call arguments. Voila: now you can define all the common dependencies as parameters on the controller constructor, and all the action-specific dependencies as parameters on the method definition.

You can see a PHP-specific description of the problem, with Action Injection as the solution, in this Symfony pull request:

https://github.com/symfony/symfony/pull/21771

You can also hear about it in this presentation from Beau Simensen, from around 32:21 to 34:31:

https://www.youtube.com/watch?v=JyrgwMagwEM&feature=youtu.be&t=1941

The Yii and Laravel containers appear to support this behavior as well, using the term “method injection.” (I think that’s a misnomer; the term appears overloaded at best, as sometimes it may mean “methods called by the DI container at object-creation time” instead of “resolving method arguments at call-time”.) Perhaps other DI containers support Action Injection as well.

… As A Code Smell

The explicit reason for using Action Injection is “to reduce dependencies or overhead” when constructing an object. You don’t want to have to pass in a dozen dependencies, when only three are used in every method, and the others are used only in specific methods.

But the fact that your controller has so many dependencies, used only in some cases and not in others, should be an indicator that the class is doing too much. Indeed, it’s doing so much that you cannot call its action methods directly; you have to use the dependency injection container not only to build the controller object but also to invoke its action methods.

Reorganizing To Avoid Action Injection

What approaches exist to help you avoid the Action Injection code smell? I assert that the better solution is to change how you organize your controller structures.

Instead of thinking in terms of “a controller class with action methods,” think in terms of “a controller namespace with action classes.” Actions are the targets for your routes anyway, not controller classes per se, so it makes sense to upgrade actions to “first-class” elements of the system. (Think of them as single-action controllers, if you like.)

Thus, instead of …

<?php
namespace App;

class BlogController {
    public function browse() { ... }
    public function read() { ... }
    public function edit() { ... }
    public function add() { ... }
    public function delete() { ... }
}

… reorganize to:

<?php
namespace App\BlogController;

class Browse { ... }
class Read { ... }
class Edit { ... }
class Add { ... }
class Delete { ... }

Then the DI container can use plain old constructor injection to create the Action object, with all of its particular dependencies. To invoke the Action, call a well-known method with the user input from the route or request. (I like __invoke() but others may prefer exec() or something similar.)

In fact, I realized only after watching the Simensen clip a second time that his example is a single-action controller in everything but name. His example code was this …

<?php
class Home {
    /**
     * @Route("/myaction", name="my_action")
     */
    public function myAction(
        Request $request,
        Router $router,
        Twig $twig
    ) {
        if (!$request->isMethod('GET')) {
            return new RedirectResponse(
                $router->generateUrl('my_action'),
                301
            );
        }

        return new Response(
            $twig->render('mytemplate.html.twig')
        );
    }
}

… but the controller action method parameters might just as well be Action class constructor parameters:

<?php
namespace Home;

class MyAction {

    public function __construct(
        Request $request,
        Router $router,
        Twig $twig
    ) {
        $this->request = $request;
        $this->router = $router;
        $this->twig = $twig;
    }

    /**
     * @Route("/myaction", name="my_action")
     */
    public function __invoke() {
        if (!$this->request->isMethod('GET')) {
            return new RedirectResponse(
                $this->router->generateUrl('my_action'),
                301
            );
        }

        return new Response(
            $this->twig->render('mytemplate.html.twig')
        );
    }
}

(UPDATE: That example code looks like it originates from Kevin Dunglas and his DunglasActionBundle -- which is itself a single-action controller implementation for Symfony.)

Action Domain Responder

For more on this organizational structure, please read my Action Domain Responder offering. ADR is a refinement of MVC that is tuned specifically to server-side request/response over-the-network interactions.

But you need not go full ADR to avoid Action Injection. Just using single-action controllers will do the trick. Then you can have well-factored single-responsibility controller classes that do not require a DI container in order to call their action methods, and Action Injection becomes a thing of the past.

Read the Reddit discussion about this post here.

Andrew Shell asks, What is the best way to handle sessions with ADR? (The problem is that the built-in PHP session extension combines the concerns of reading input, managing storage, and sending output; the solution is a domain-layer session-data manager.)

I’ve reached a point with a couple of my Radar projects where I need to add a login and set permissions. I’m trying to figure out the best way to handle this, especially with PSR-7 and ADR. ...

[In Action-Domain-Responder] it’s ok to read the session cookie in an Input class, and it’s ok to write the cookie in a Responder class, but pretty much everything else should be in the Domain layer. ...

[In the Domain layer,] Cadre.DomainSession takes a session id (or generates one) and loads session data from storage. It’s smart enough to handle regenerating session ids and cleaning up expired sessions.

Read the whole article at FutureProof PHP for examples and links!

UPDATE: Reddit discussion.