I have always struggled with how packages are versioned and published to the npm registry.
My main concern is that you probably want to also add a git tag to your source code when you are releasing a new version, but npm packages have their own versioning system, and include a &quot;version&quot; field in the package.json
Because of this, most of the workflows I have seen, usually involve:
<ol>
<li>Running <code>npm version ...</code>. This will update the &quot;version&quot; field in the package.json file.</li>
<li>Publishing the package to the npm registry, using the version set in previous step.</li>
<li>Committing to git, so that we track the change in package.json file.</li>
<li>Adding a git tag.</li>
<li>Pushing to git remote to track new commit and new tag.</li>
</ol>
<blockquote>
Steps 3 and 4 are frequently done automatically as part of <code>npm version</code>.
</blockquote>
For me this flow has two main problems:
<ul>
<li>
My personal preference is that everything is driven by git tags, making them the single source of truth.
This would allow to just have one manual step -&gt; <code>git tag -a v1.0.0 -m &quot;...&quot; &amp;&amp; git push origin --tags</code>. Then, this would trigger a number of potential automations, including publishing to the npm registry, but also others like creating a release with the appropriate release notes, building release artifacts, etc.
</li>
<li>
The &quot;version&quot; field in the package.json file can very easily become outdated, if you git-tag by mistake before publishing the package, or if pushing the changes fails after <code>npm version ...</code> has been run.
I&#x27;ve seen this happening more often than it seems.
</li>
</ul>
Because of this, my current take when publishing npm packages for my personal projects is:
<ol>
<li>
Get rid of the &quot;version&quot; field from the package.json file. It&#x27;s misleading in source code, as it can very easily be out of date.
The only case where it&#x27;s useful is when the package has been installed and is inside node_modules, as other packages will assume this field to exist and have the right value on it.
In this case it&#x27;s always going to be correct due to the<code>npm version ...</code> + <code>npm publish</code> tandem (see next point).
</li>
<li>
Creating the git tag is the only &quot;manual step&quot;. This triggers an automation running <code>npm version ${GIT_TAG} --git-tag-version=false &amp;&amp; npm publish</code> (this is simplified. You probably also need to build your project and other potential extra steps).
The version to publish is inferred from the git tag (<code>${GIT_TAG}</code> is just a placeholder), and only at this stage we will set the &quot;version&quot; inside package.json, just before the package is published.
</li>
<li>
Other automations that need to happen during releases, can be also triggered now, like publishing release notes, building artifacts, etc.
</li>
</ol>
<blockquote>
As an example, you can see <a target="_blank" rel="noopener noreferrer" href="https://github.com/shlinkio/github-actions/blob/24de7a2b89a9eb11b0acfd184de7187698b051b6/.github/workflows/js-lib-publish.yml">this GitHub actions workflow</a>, which follows this approach.
</blockquote>

I have always struggled with how packages are versioned and published to the npm registry. My main concern is that you probably want to also add a git tag to your source code when you are releasing a new version, but npm packages have their own versioning system, and include a "version" field in…

My current take when publishing packages to the npm registry

A couple of weeks ago I migrated a React project using redux to <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/">Redux Toolkit</a>.
Redux has always been my preferred state management tool for React (which doesn&#x27;t mean I &quot;love&quot; it), but one of its main problems is the amount of boilerplate code it requires.
Because of that I had a couple of helper functions, but there was still some things not properly handled, like proper type inference on reducers and actions (I use TypeScript).
A bit by accident (I think it was on Twitter), I found out about Redux Toolkit (RTK from now on), an official library from the redux team, which provides some opinionated helpers to reduce the amount of boilerplate, and I decided to give it a chance.
These are my impressions.
<h3>TL;DR</h3>
I first started to use it in a proof of concept, and I quickly loved it.
RTK does not &quot;replace&quot; any of the redux principles, so you can progressively adopt it, by replacing small bits of code. My plan was to use it just for some reducers, but I liked it so much that I ended up migrating the whole project in a series of consecutive pull requests.
<h3>A bit of context</h3>
Before the migration, I used to follow the <a target="_blank" rel="noopener noreferrer" href="https://github.com/erikras/ducks-modular-redux">ducks modular pattern</a>, which promotes putting all your action types, action creators and the reducer handling those actions on the same module.
This fits pretty well with RTK, as in most of the cases you will use <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/api/createSlice">slices</a>, and end up exporting the reducer and action creators returned by it, from the same module.
If you use <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/api/createAsyncThunk">async thunks</a>, they usually need to be used by that same slice, so it&#x27;s not a bad idea to export them also from there.
<h3>Why I love it</h3>
There are a couple of reasons for which I loved RTK right away. The main one is that they make an impressive work on making type inference in TypeScript work properly.
<ul>
<li>Slices detect the type of the initial state in order to know what is expected to be passed as <code>state</code> to reducers.</li>
<li>You can infer the type of your store from what is generated by <code>configureStore</code> or <code>combineReducers</code> functions, allowing you to also properly type the <code>dispatch</code> function.</li>
<li>Action creators are generated with the proper param types based on the reducers provided to <code>createSlice</code> or the callback provided to <code>createAsyncThunk</code>.</li>
<li><code>createSlice</code> can consume all the action creators generated by <code>createAsyncThunk</code>, and infer the proper payload for each one of them.</li>
</ul>
Thanks to this, the code is super predictable and potential bugs can be caught sooner.
<blockquote>
More details on how to use RTK with typescript https://redux-toolkit.js.org/usage/usage-with-typescript
</blockquote>
But this is not the only benefit. Other reasons that make it very nice to work with are:
<ul>
<li>It keeps the same concepts from Redux, but removing the boilerplate or your own helper functions if you have them (yes, I didn&#x27;t want to keep all those <code>switch</code> statements everywhere).</li>
<li>It is mostly transparent for the components dispatching the actions or consuming the state.</li>
<li>All the tests covering your reducers/actions/components should keep passing, as the outcome from RTK is the same as if you built everything manually.</li>
<li>It introduces a couple of extra helpers, like <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/rtk-query/overview">RTK query</a> or the <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/api/createListenerMiddleware">listener middleware</a>, which is very useful to dispatch actions as a result of other actions being dispatched.</li>
</ul>
<h3>Challenges I found</h3>
Of course, adopting a new tool always comes with some challenges.
The main &quot;problem&quot; I found is that RTK is a bit opinionated, but that&#x27;s precisely how they manage to reduce boilerplate code, and it&#x27;s also &quot;advertised&quot; in their website, so not a big surprise.
I usually prefer to be in control of everything (configuration over convention), but that&#x27;s just a personal preference, and sometimes it&#x27;s ok to accept a bit of magic for the sake of simplicity.
This caused the next challenges for my particular case:
<ul>
<li>
RTK assumes your project follows a strict <a target="_blank" rel="noopener noreferrer" href="https://redux.js.org/tutorials/fundamentals/part-7-standard-patterns#flux-standard-actions">Flux pattern</a>, meaning your actions always have the properties <code>type</code>, <code>payload</code> and optionally <code>meta</code> and <code>error</code>.
I was not following this pattern (my actions had the payload &quot;mixed&quot; on the first object level), so I had to adapt all my actions first, fix the tests, then migrate the reducer to RTK and make sure the tests kept passing.
<div></div>
</li>
<li>
Immutability is no longer promoted in reducers. Instead, the library requires <a target="_blank" rel="noopener noreferrer" href="https://immerjs.github.io/immer/">immer</a> internally, and using proxies they automatically ensure immutability, even if you &quot;mutate&quot; the state.
This feels a bit counterintuitive at first, because redux always promoted an immutable approach, and the use of immer is not obvious.
However, they have <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/usage/immer-reducers#why-immer-is-built-in">good reasons</a> to do it, and if your reducers return a state object, you can still use the immutable approach. It&#x27;s up to you.
<div></div>
</li>
<li>
Action creators resulting of <code>createAsyncThunk</code> can only have one argument.
This is because the async thunk callback receives a second argument containing the <code>dispatch</code> and <code>getState</code> functions, as well as a couple of other goodies, enforcing this convention to avoid human errors.
<div></div>
</li>
<li>
You cannot dispatch other actions after the callback passed to <code>createAsyncThunk</code>, because it has to return the payload and RTK dispatches the action for you.
However, this is probably something you usually should not be doing, and in my case, I resolved it with the <a target="_blank" rel="noopener noreferrer" href="https://redux-toolkit.js.org/api/createListenerMiddleware">listener middleware</a>, listening for the second action in order to dispatch the second one.
</li>
</ul>
<h3>Conclusion</h3>
My conclusion is that RTK is definitely worth it if you use redux.
It makes code simpler, more predictable and better typed. However, it still requires knowing how redux works internally and what are its patterns, in order to understand why the library exposes the helpers it exposes and why.
For existing redux projects, you can migrate progressively, addressing the challenges bit by bit and not all at once, which simplifies its adoption.
For new projects in which you want to use redux, I would recommend starting right away with RTK.

A couple of weeks ago I migrated a React project using redux to Redux Toolkit. Redux has always been my preferred state management tool for React (which doesn't mean I "love" it), but one of its main problems is the amount of boilerplate code it requires.

Because of that I had a couple of helper…

My experience migrating to Redux Toolkit (RTK)

In 2019, GitHub published their own solution to run automated workflows called GitHub Actions, which allowed those hosting their code in GitHub, to be able to define and run their CI/CD pipelines in the same platform. When it was released, one of the main pain points to use it was that defining…

How to reduce duplication in your GitHub Actions workflows

Recently ReactJS v18 was released. I started to look into its improvements, and checked which of my projects could benefit from them.
The main react-based project I maintain at the moment of writing this article is <a target="_blank" rel="noopener noreferrer" href="https://github.com/shlinkio/shlink-web-client">shlink-web-client</a>, so I naturally created a new branch and started the process.
The update was quite smooth, as most of the other dependencies I was using from the react ecosystem were already updated to support v18. All but one, <a target="_blank" rel="noopener noreferrer" href="https://enzymejs.github.io/enzyme/">enzyme</a>, the testing framework I was using to unit-test react components.
To be precise, I was able to continue running my tests, but some of them (those using <code>mount</code> instead of <code>shallow</code>) were still rendering components with the &quot;old&quot; React v17 approach, causing them to behave as in that version and a warning being printed in the console.
<h3>First fix attempt</h3>
The way enzyme integrates with the react version you are using is through an adapter library. The last official one supports only React v16, but someone released an <a target="_blank" rel="noopener noreferrer" href="https://github.com/wojtekmaj/enzyme-adapter-react-17">unofficial adapter for v17</a> which, with close to 650k weekly downloads, quickly became the way to go.
I checked if there was one for React 18, but sadly there wasn&#x27;t.
Also, the author of the adapter for v17 posted an article indicating <a target="_blank" rel="noopener noreferrer" href="https://dev.to/wojtekmaj/enzyme-is-dead-now-what-ekl">enzyme is dead</a>, he was not going to release one for v18, and publishing one for v17 was a mistake.
With those facts in mind, I started to face what was probably going to be the moment to migrate to <a target="_blank" rel="noopener noreferrer" href="https://testing-library.com/docs/react-testing-library/intro">react testing library</a>.
<h3>Migration strategy</h3>
I decided to follow a migration strategy similar to the one suggested in the article above, but with a couple of modifications:
<ul>
<li>I update to React 18 anyway, as tests still pass.</li>
<li>Migrate right away all tests using <code>mount</code>, as those are the ones behaving differently.</li>
<li>New tests should be written directly with react testing library (RTL from now on).</li>
<li>When an existing test needs to be changed, consider migrating it to RTL, and do it if there&#x27;s time.</li>
<li>Introduce some PR from time to time just migrating a handful of tests.</li>
<li>Once everything is migrated, get rid of everything related with enzyme.</li>
</ul>
<h3>First contact and impressions</h3>
I was a bit sceptical with RTL, as it was focused more on integration tests, instead of unit tests, which meant I had to completely change the mindset to write tests.
It also didn&#x27;t support shallow rendering, meaning that you will end up sometimes rendering a bigger component tree when testing container-like components, potentially causing side effects that could affect your test.
On the other hand there&#x27;s more and more people stating that <a target="_blank" rel="noopener noreferrer" href="https://kentcdodds.com/blog/why-i-never-use-shallow-rendering">shallow rendering is an anti-pattern</a>, and that&#x27;s probably the reason of enzyme getting &quot;discontinued&quot;.
Also, RTL has become the <a target="_blank" rel="noopener noreferrer" href="https://reactjs.org/docs/testing.html#tools">officially recommended framework</a> to test react components, it has become very popular, and it has even joined a wider group of testing libraries under the <a target="_blank" rel="noopener noreferrer" href="https://testing-library.com/"><code>@testing-library</code></a> organization.
The thing is that I started to use it, and I was quickly surprised with how it felt to work with it, and all the benefits it was bringing to my tests.
<h3>Benefits I have experienced</h3>
Once I started migrating the first tests I noticed some benefits:
<ul>
<li>Changing my mindset was actually easier than I thought. The docs are very well written, so it&#x27;s relatively easy to start using RTL.</li>
<li>My tests got simpler, and required less of those nasty global mocks that jest allows (I&#x27;m looking at you, <a target="_blank" rel="noopener noreferrer" href="https://jestjs.io/es-ES/docs/mock-functions#mocking-modules"><code>jest.mock</code></a>).</li>
<li>Tests were way less coupled with implementation details. I moved from testing the component props, to test what the user would see on the screen.</li>
<li>Related with previous point, I started to write my tests by looking at the screen instead of the component&#x27;s implementation.</li>
<li>Changes in source code led to fewer tests requiring to be changed.</li>
<li>A progressive migration was possible, where some tests still use enzyme and others are already using RTL.</li>
</ul>
And overall, it felt good and I have already dedicated a couple of PRs just to migrate more tests.
<h3>Challenges I faced</h3>
But of course, migrating to a new tool always comes with its own challenges, and this was not an exception. I&#x27;ll explain the main ones I have faced so far and how I tackled them:
<ul>
<li>
RTL lets you do some things in a couple of different ways, and the docs may not be super clear about what&#x27;s the recommended option.
For this I recommend reading <a target="_blank" rel="noopener noreferrer" href="https://acel.me/DCMb1">this article</a> from Kent C. Dodds, RTL&#x27;s author, which explains some common mistakes when using the library.
</li>
<li>
At first, I struggled a bit with asynchronous side effects and state changes in components, which can easily end up printing a warning like <code>Warning: An update to MyComponent inside a test was not wrapped in act</code>.
The warning also explains how you are supposed to solve this by wrapping your code in <code>act()</code>, but this warning comes from React, not RTL, and what it is not telling you is that RTL already wraps all needed operations in <code>act()</code>.
What this error usually mean is that you are not waiting for something to happen. <a target="_blank" rel="noopener noreferrer" href="https://acel.me/jnUdT">This other article</a>, also from Kent C. Dodds, explains everything you need to know about the things that can lead to this warning, and how to solve them.
</li>
<li>
Since you start testing from the user point of view, some use cases can be challenging to test without coupling with implementation details. For example, when you have a component which dynamically renders different images or icons, I used to directly check the component properties.
For this I found the best solution was to use <a target="_blank" rel="noopener noreferrer" href="https://jestjs.io/docs/snapshot-testing">jest snapshots</a>. I didn&#x27;t want to manually check which SVG was being rendered in the DOM, just that different ones were being used in every case.
<pre class="language-tsx"><code class="language-tsx">// I went from this...
test(&#x27;...&#x27;, () =&gt; {
 const wrapper = shallow(&lt;MyComp dynamicValue=&quot;foo&quot; /&gt;);
 expect(wrapper.find(FontAwesomeIcon).prop(&#x27;icon&#x27;)).toEqual(someIcon);
})

// To this
test(&#x27;...&#x27;, () =&gt; {
 const { container } = render(&lt;MyComp dynamicValue=&quot;foo&quot; /&gt;);
 expect(container.firstChild).toMatchSnapshot();
})
</code></pre>
</li>
<li>
Something very similar happens if you use some library that renders canvas. There&#x27;s no way to test that from a DOM point of view, which is what RTL does.
In my case I was using <a target="_blank" rel="noopener noreferrer" href="https://www.chartjs.org/">Chart.js</a> to render some charts, so I used <a target="_blank" rel="noopener noreferrer" href="https://github.com/hustcc/jest-canvas-mock">jest-canvas-mock</a>, which exposes a method on the canvas to see which are all the events invoked from the library.
Then I used snapshots again to verify they had the expected &quot;shape&quot;.
<pre class="language-tsx"><code class="language-tsx">// I went from this...
test(&#x27;...&#x27;, () =&gt; {
 const wrapper = shallow(&lt;MyCompWithCanvas /&gt;);
 expect(wrapper.find(Chart).prop(&#x27;data&#x27;).datasets).toEqual(...);
})

// To this
test(&#x27;...&#x27;, () =&gt; {
 const { container } = render(&lt;MyCompWithCanvas /&gt;);
 const events = container.querySelector(&#x27;canvas&#x27;)?.getContext(&#x27;2d&#x27;)?.__getEvents();

 expect(events).toBeTruthy();
 expect(events).toMatchSnapshot();
})
</code></pre>
</li>
</ul>
<h3>Conclusion</h3>
For better or worst, enzyme should no longer be considered an option. If you are starting a new project or are using it on small ones, consider migrating to RTL as soon as possible.
If you are using it in bigger projects, following the process described in this article will probably help you.
In any case, you will get surprised. React testing library is a great tool and provides many benefits over enzyme.
Its main issue is that it&#x27;s not a drop-in replacement for enzyme, so you will have to change a bit your mindset.

Recently ReactJS v18 was released. I started to look into its improvements, and checked which of my projects could benefit from them. The main react-based project I maintain at the moment of writing this article is shlink-web-client, so I naturally created a new branch and started the process.

The…

My experience migrating from enzyme to react testing library

Capturing code coverage for a test suite is a very useful way to know which parts of your source code are actually getting executed by tests. This is useful not only to know if you need to add more tests to your project (in case the coverage is too low), but also, if you want to apply technics like…

Capturing remote code coverage in API tests with PHPUnit

Some time ago I created a Zend Framework 2 module designed to wrap Zend\Mail and ease sending emails in a Zend Framework 2 application. I was copy-pasting the code of that module in many applications so I decided it was a good candidate to become an independent module. After creating it I pushed it…

Send emails in a Zend Framework 2 application using ZF2-AcMailer module

Dependency management is very important in any kind of project. Any application will need to use third party libraries to avoid to reinvent the wheel.
The problem is that getting each one of them from a different place takes time, and it&#x27;s not easy to be sure we get the correct version.
To solve this in java projects we can use an automated dependency manager, like <a target="_blank" rel="noopener noreferrer" href="https://maven.apache.org/">Maven</a>, which is really a building system with dependcy management included. The problem with maven is that it could be hard to use, and not very intuitive.
Instead of Maven, I rather prefer to use <a target="_blank" rel="noopener noreferrer" href="https://ant.apache.org/ivy/">Ivy</a>. It is a more simple and agile dependency management system, designed to be used with <a target="_blank" rel="noopener noreferrer" href="https://ant.apache.org/">Ant</a>, but it takes dependencies from Maven repositories, like <a target="_blank" rel="noopener noreferrer" href="https://mvnrepository.com/">Maven central</a>.
<h3>Getting started</h3>
To use Ivy we need to create an <code>ivy.xml</code> file in the project root directory. It will be used to define which dependencies are needed by our project, and will need to be downloaded at building time.
This is the <a target="_blank" rel="noopener noreferrer" href="https://github.com/acelaya/subclient-subconnector">Subconnector</a> Ivy script.
<pre class="language-xml"><code class="language-xml">&lt;ivy-module version=&quot;2.0&quot;&gt;
 &lt;info organisation=&quot;net.subclient&quot; module=&quot;subconnector&quot; /&gt;

 &lt;dependencies&gt;
 &lt;dependency org=&quot;junit&quot; name=&quot;junit&quot; rev=&quot;4.10&quot; /&gt;
 &lt;dependency org=&quot;com.google.code.gson&quot; name=&quot;gson&quot; rev=&quot;2.2.2&quot; /&gt;
 &lt;dependency org=&quot;log4j&quot; name=&quot;log4j&quot; rev=&quot;1.2.17&quot; /&gt;
 &lt;dependency org=&quot;org.apache.commons&quot; name=&quot;commons-lang3&quot; rev=&quot;3.1&quot;/&gt;
 &lt;/dependencies&gt;
&lt;/ivy-module&gt;
</code></pre>
As you can see, it is very simple. We just defined an info element with the basic project information, and a dependencies element with nested information of each of the dependencies of the project.
For each one of them we have to know its organization, name and revision. With this we can be sure we will get the desired library and revision.
But how do we know what to put in <code>org</code>, <code>name</code> and <code>rev</code> attributes? The <a target="_blank" rel="noopener noreferrer" href="https://mvnrepository.com/">maven central repository</a> webpage will help us with this.
At the top search bar we can write the name of a library, for example gson. The first result corresponds to the gson artifacts in the maven central. By selecting the desired version we will get the dependency element for an Ivy script, as well as other dependency management systems, like Maven or <a target="_blank" rel="noopener noreferrer" href="https://gradle.org/">Gradle</a>.
<img src="/assets/img/dependency.jpg" alt="Maven dependency example"/>
We just need to copy and paste it. Nice and easy.
<h3>Automate retrieving dependencies</h3>
Once our Ivy script is ready, it is time to include retrieving dependencies in our building process. The easiest way to do it is to create an Ant target in our <code>build.xml</code> script, like this.
<pre class="language-xml"><code class="language-xml">&lt;target name=&quot;retrieve-dependencies&quot;
 description=&quot;Retrieve dependencies with Apache IVY&quot;&gt;

 &lt;ivy:retrieve type=&quot;jar&quot; /&gt;

&lt;/target&gt;
</code></pre>
This will look for the ivy.xml script and download dependencies defined on it in a lib folder, but only binary jar files. If <code>type=&quot;jar&quot;</code> is removed, all docs, sources and binaries will be retrieved.
Make sure to add Ivy binaries to Ant classpath to make it properly work. The <code>project</code> element in the build script will need also to look like this.
<pre class="language-xml"><code class="language-xml">&lt;project basedir=&quot;.&quot; default=&quot;build&quot; name=&quot;Subconnector&quot; xmlns:ivy=&quot;antlib:org.apache.ivy.ant&quot;&gt;

 ...

&lt;/project&gt;
</code></pre>
Notice the <code>xmlns:ivy</code> attribute.
Now we are ready to go.
For an advanced Ivy configuration take a look at its <a target="_blank" rel="noopener noreferrer" href="https://ant.apache.org/ivy/history/2.3.0/index.html">official documentation</a>. It explains how to use custom repositories, how to set up a proxy server, how to change default local lib folder, etc.

Dependency management is very important in any kind of project. Any application will need to use third party libraries to avoid to reinvent the wheel. The problem is that getting each one of them from a different place takes time, and it's not easy to be sure we get the correct version.

To solve…

Dependency management in Java projects with Ant and Ivy

Any programmer that is used to use Zend Framework version 1 will have been in the situation that Zend Framework version 2 has removed Controller Plugins as they were in the first version of the framework.
Controller Plugins used to allow us to attach code to be executed at some points of the execution process, regardless the controller that was being used.
Two of the most used Controller Plugin methods were <code>preDispatch()</code> and <code>postDispatch()</code>. These methods were executed just before and after the corresponding action, which was very useful to handle common stuff, like checking if current user is logged in or has a propper role to do what he is trying to do.
Puting this check on <code>preDispatch()</code> allowed us to redirect the user to the login or display a 403 page, without duplicating code, which would have made the application difficult to maintain.
<h3>The Zend Framework 2 behavior.</h3>
As I said earlier, this behavior has been removed from the framework in the last version. Now a new event-based system is present, which allows us to register code execution to certain situations, even create aour own &quot;situations&quot; to be handled.
One of those events is the dispatch MVC event, which is triggered at the moment the controller action is executed. That is the event we will nedd to handle.
This is an example of a basic Module class where the dispatch event is prepared to be catched when it occurs.
<pre class="language-php"><code class="language-php">&lt;?php
namespace Application;

use Zend\Mvc\ModuleRouteListener;
use Zend\Mvc\MvcEvent;
use Zend\ModuleManager\Feature\ConfigProviderInterface;
use Zend\ModuleManager\Feature\AutoloaderProviderInterface;

class Module implements ConfigProviderInterface, AutoloaderProviderInterface
{
 public function onBootstrap(MvcEvent $e)
 {
 $eventManager = $e-&gt;getApplication()-&gt;getEventManager();
 $moduleRouteListener = new ModuleRouteListener();
 $moduleRouteListener-&gt;attach($eventManager);

 $eventManager-&gt;getSharedManager()-&gt;attach(__NAMESPACE__, MvcEvent::EVENT_DISPATCH, function ($e) {
 // This is executed on dispatch event
 });
 }

 public function getConfig()
 {
 return include __DIR__ . &#x27;/config/module.config.php&#x27;;
 }

 public function getAutoloaderConfig()
 {
 return array(
 &#x27;Zend\Loader\StandardAutoloader&#x27; =&gt; array(
 &#x27;namespaces&#x27; =&gt; array(
 __NAMESPACE__ =&gt; __DIR__ . &#x27;/src/&#x27; . __NAMESPACE__,
 ),
 ),
 );
 }
}
</code></pre>
The onBootstrap() method is automatically called when the bootsrap MVC event is triggered on this module, which is one of the firt things that happen when a module is loaded.
In there we have registered an event handler for the dispatch MVC event of this module, by attaching a callback that will be executed when the controller action is called.
The problem is that this code will be called just after the action. To ensure that code is executed before the action (<code>preDispatch()</code>) we need to add a priority when the event handler is attached.
<pre class="language-php"><code class="language-php">$eventManager-&gt;getSharedManager()-&gt;attach(__NAMESPACE__, MvcEvent::EVENT_DISPATCH, function ($e) {
 // This is executed on preDispatch
}, 100);
</code></pre>
Default priority is 1, so any number greater than 1 will make the event to be triggered before.
By using a negative priority we ensure the event is called after the action (postDispatch()), but this is the default behavior.
<pre class="language-php"><code class="language-php">$eventManager-&gt;getSharedManager()-&gt;attach(__NAMESPACE__, MvcEvent::EVENT_DISPATCH, function ($e) {
 // This is executed on postDispatch
}, -100);
</code></pre>
Attaching multiple event handlers will make the to be executed in order of priority or in the order they were attached when they have the same priority.
Event handlers could be attached to other MVC events, which will allow us to handle other situations. For a full list of MVC events refer to <a target="_blank" rel="noopener noreferrer" href="https://akrabat.com/a-list-of-zf2-events/">this Akrabat&#x27;s article</a>.

Any programmer that is used to use Zend Framework version 1 will have been in the situation that Zend Framework version 2 has removed Controller Plugins as they were in the first version of the framework. Controller Plugins used to allow us to attach code to be executed at some points of the…