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Abstract

do that:</p><div id="2e8b"><pre>eventHandler<span class="hljs-selector-class">.Handle</span>(event1, <span class="hljs-built_in">ExampleMiddlewareFoo</span>(<span class="hljs-built_in">ExampleMiddlewareBar</span>(handle)))</pre></div><h1 id="a8a5">Managing Events with Handlers and Middleware</h1><p id="f869">Most articles I read explain how to use this design pattern; this one deals with implementing the internal logic. So let's start coding.</p><p id="35c4">The full code for this article can be found <a href="https://github.com/xNok/slack-go-demo-socketmode/blob/main/examples/middleware/main.go">here</a> to help you follow along.</p><h2 id="0f88">Designing events</h2><p id="b622">First, we are going to enumerate the list of events that our system can handle. The way we create enumeration in Go is a bit different than in other programming languages. In Go, we are going to use a set of constants sharing the same <code>type</code>. Here I define a type <code>EventType</code>that represents a string with the event's name.</p><div id="b181"><pre>// <span class="hljs-keyword">type</span> <span class="hljs-type">used </span>to enumerate events <span class="hljs-keyword">type</span> <span class="hljs-type">EventType </span>string</pre></div><div id="4817"><pre>const ( event1 EventType <span class="hljs-operator">=</span> <span class="hljs-string">"event1"</span> event2 EventType <span class="hljs-operator">=</span> <span class="hljs-string">"event2"</span> )</pre></div><p id="e041">Next, we define the event itself. In our example, the<code>Event</code> as a type which can be selected among the list of <code>EventType</code> created above.</p><div id="2bc9"><pre><span class="hljs-keyword">type</span> <span class="hljs-type">Event</span> struct { <span class="hljs-type">Type</span> <span class="hljs-type">EventType</span> <span class="hljs-type">Data</span> interface{} }</pre></div><h2 id="df6c">Create an event sender (for test purpose)</h2><p id="60aa">To test our system, we will need to create a small function to send events every 2s. Each<code>Event</code> is transmitted via a <a href="https://tour.golang.org/concurrency/2">channel</a> and, the <code>eventSender</code> below sends a random <code>Event</code> of type <code>event1</code> or <code>event2</code> to a channel.</p><blockquote id="53f3"><p><i>Channels are a type which you can send and receive values, they are great for communication among goroutines. In other words, there are perfect for sending and receive event through your application.</i></p></blockquote><div id="ffd1"><pre><span class="hljs-function"><span class="hljs-keyword">func</span> <span class="hljs-title">eventSender</span><span class="hljs-params">(c <span class="hljs-keyword">chan</span> EventType)</span></span> {</pre></div><div id="7f57"><pre> for { // Send <span class="hljs-selector-tag">a</span> random event <span class="hljs-selector-tag">to</span> the channel rand<span class="hljs-selector-class">.Seed</span>(<span class="hljs-selector-tag">time</span><span class="hljs-selector-class">.Now</span>()<span class="hljs-selector-class">.Unix</span>()) events := []EventType{ event1, event2, } n := rand.<span class="hljs-built_in">Int</span>() % <span class="hljs-built_in">len</span>(events)</pre></div><div id="6101"><pre> c <- events[n] <span class="hljs-comment">// send event to channel</span></pre></div><div id="5285"><pre> // <span class="hljs-keyword">wait</span> a <span class="hljs-built_in">bit</span> <span class="hljs-built_in">time</span>.Sleep(<span class="hljs-number">2</span> * <span class="hljs-built_in">time</span>.Second) } }</pre></div><h2 id="000c">Handler and dispatcher</h2><p id="e562">We first need a struct to hold the list of events we want to listen to and which function to call whenever that event is transmitted. This struct also contains the channel used for communicating events.</p><div id="280d"><pre><span class="hljs-comment">// Create a struct to hold config</span> <span class="hljs-comment">// And simplify dependency injections</span> <span class="hljs-keyword">type</span> EventHandler <span class="hljs-keyword">struct</span> { <span class="hljs-comment">// Event channel</span> Events <span class="hljs-keyword">chan</span> Event <span class="hljs-comment">// hold the registedred event functionss</span> EventMap <span class="hljs-keyword">map</span>[EventType][]<span class="hljs-function"><span class="hljs-keyword">func</span><span class="hljs-params">(Event)</span></span> }</pre></div><p id="aa6c">Next, we need to provide an initializing constructor for our <code>EventHandler</code>.</p><div id="a4ed"><pre><span class="hljs-function"><span class="hljs-keyword">func</span> <span class="hljs-title">NewEventHandler</span><span class="hljs-params">()</span></span> *EventHandler { eventMap := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[EventType][]<span class="hljs-function"><span class="hljs-keyword">func</span><span class="hljs-params">(Event)</span></span>) event

Options

s := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">chan</span> Event)</pre></div><div id="78bb"><pre> return <span class="hljs-variable">&</span>EventHandler<span class="hljs-punctuation">{</span> <span class="hljs-symbol"> Events:</span> events, <span class="hljs-symbol"> EventMap:</span> eventMap, <span class="hljs-punctuation">}</span> <span class="hljs-punctuation">}</span></pre></div><p id="98fe">Then, we can create our <code>Handle</code> function that associates the event with a callback function.</p><div id="308c"><pre><span class="hljs-comment">// register the handler function to handle an event type</span> func (h *EventHandler) <span class="hljs-built_in">Handle</span>(e EventType, f <span class="hljs-built_in">func</span>(Event)) { h<span class="hljs-selector-class">.EventMap</span><span class="hljs-selector-attr">[e]</span> = <span class="hljs-built_in">append</span>(h<span class="hljs-selector-class">.EventMap</span><span class="hljs-selector-attr">[e]</span>, f) }</pre></div><p id="e42a">Finally, we create the <code>EventDispatcher</code> function, the core of this mechanism. The <code>EventDispatcher</code>process any event sent to a channel, check its type, and if any function has been registering for that type, we call all registered functions.</p><div id="6597"><pre><span class="hljs-function"><span class="hljs-keyword">func</span> <span class="hljs-params">(h *EventHandler)</span></span> EventDispatcher() { <span class="hljs-keyword">for</span> evt := <span class="hljs-keyword">range</span> h.Events { log.Printf(<span class="hljs-string">"event recieved: %v"</span>, evt) <span class="hljs-keyword">if</span> handlers, ok := h.EventMap[evt.Type]; ok { <span class="hljs-comment">// If we registered an event</span> <span class="hljs-keyword">for</span> _, f := <span class="hljs-keyword">range</span> handlers { <span class="hljs-comment">// exacute function as goroutine</span> <span class="hljs-keyword">go</span> f(evt) } } } }</pre></div><h1 id="13e4">Using our system</h1><p id="4d4e">Everything is ready; we can start using our event handling system.</p><ol><li>Instantiate our event Handler</li><li>Register which event to listen to and what function to callback</li><li>Start the event sender</li><li>Start the event dispatcher</li></ol><div id="62ab"><pre><span class="hljs-keyword">func</span> <span class="hljs-title function_">main</span><span class="hljs-params">()</span> {</pre></div><div id="5b09"><pre> <span class="hljs-variable">eventHandler</span> := <span class="hljs-function"><span class="hljs-title">NewEventHandler</span>()</span></pre></div><div id="d244"><pre> eventHandler.Handle(event1, <span class="hljs-keyword">func</span><span class="hljs-params">()</span> { <span class="hljs-built_in">log</span>.Printf(<span class="hljs-string">"event Handled: %v"</span>, event1) })</pre></div><div id="5c56"><pre> <span class="hljs-variable">go</span> <span class="hljs-function"><span class="hljs-title">eventSender</span>(<span class="hljs-variable">eventHandler.Events</span>)</span></pre></div><div id="30f2"><pre> eventHandler<span class="hljs-selector-class">.EventDispatcher</span>()</pre></div><div id="9bf2"><pre>}</pre></div><p id="e590">The result should be along those lines:</p><figure id="5ee7"><img src="https://cdn-images-1.readmedium.com/v2/resize:fit:800/1*_D-GCRSu3K8CgTBXewJjJQ.gif"><figcaption></figcaption></figure><p id="19d6">Since we only handle an event of type <code>event1</code>, only <code>event1</code> shows as <code>Hansled</code>. All is good!</p><p id="d48a">The full code for this article can be found <a href="https://github.com/xNok/slack-go-demo-socketmode/blob/main/examples/middleware/main.go">here</a>.</p><h1 id="6f5e">Interesting Articles tackling the same topic</h1><ul><li><a href="https://drstearns.github.io/tutorials/gomiddleware/">Middleware Patterns in Go</a></li><li><a href="https://sathishvj.medium.com/web-handlers-and-middleware-in-golang-2706c2ecfb75">Web Handlers and Middleware in GoLang</a></li><li><a href="https://readmedium.com/lightweight-event-management-implemented-by-go-a654d59ac65">Lightweight event management implemented by Go</a></li><li><a href="https://readmedium.com/the-7-most-important-software-design-patterns-d60e546afb0e">The 7 Most Important Software Design Patterns</a></li></ul><p id="13e7"><i>Do you want <b>unlimited access</b> to all my content and many other writers’ content on Medium? Consider using my affiliate link to <a href="https://couedeloalexandre.medium.com/membership">become a Medium member today</a></i></p><h2 id="853a">Further reads</h2> <figure id="81d2"> <div> <div> <img class="ratio" src="http://placehold.it/16x9"> <iframe class="" src="https://couedeloalexandre.medium.com/embed/list/3f9d03f2cb8f" allowfullscreen="" frameborder="0" height="184" width="undefined"> </div> </div> </figure></iframe></div></div></figure></article></body>

How to Update Your Emotions to Reduce Stress

You wouldn’t eat last month’s pizza, so why snack on old painful events?

Do you consume yesterday’s emotional baggage? Many of your concerns stem from the past and have no power over you apart from what you give them.

Those painful events are finished in the world outside your head. For you, though, they might continue. Perhaps you keep them going with negative thoughts. Nonetheless, you can let go of stress if you update your emotions.

Emotional baggage

Plenty of people feel the pressure of emotional baggage; resentment, anger, blame, and the list could go on. If you harbor ill will, regret how you’ve behaved, or lament over other old experiences, your emotions are out of date.

If they were foods, you would have thrown them out, recognizing they have no nourishing content and might be poisonous. Indeed, stale emotions can make you ill just like last month’s pizza.

Why you’ve stored emotional angst

Don’t be hard on yourself for hanging onto your painful past. Your mind stores old experiences you don’t enjoy for future reference. The idea is to avoid potential disasters by not repeating mistakes. The only trouble is, it’s best not to overplay stressful recollections. When you go over them, you make them worse.

Your current perception colors your memory, and your brain filters data that doesn’t match your beliefs. Thus, the contents of your baggage change over time. Your mind might take out or add details, strengthening the ideas you have today.

You may also maintain negativity because of a sense of injustice. If you think others mistreated you, you might feel you haven’t resolved problems. Keeping them going with negative thoughts is your way of waiting for harmony to return. You can’t fix painful experiences with repetitive thoughts, though.

How to update your emotions

So how can you update your emotions and put old concerns to rest?

Find value in events

The first step is to learn from the past. Research shows people let go of trauma when they find value in what happened to them. Examine your mental angst, however painful, and discover what it can teach you.

Stay present

Next, change the habit of going over your past by living in the moment. Bring your attention to the present when thoughts drift to painful memories. Focus on what occurs now, like breathing or other actions you carry out. Examine your surroundings. What’s happening?

Increase gratitude

Also, strengthen your focus on the present by looking at what’s good in life. Before you sleep at night, count your blessings. Maybe you’ve got excellent health, a loving relationship, or a good job.

Or, perhaps you love your pet dog, your beautiful garden, or where you live. Certainly, you have your future ahead of you and many choices to make. There are always reasons to feel gratitude.

If you carry around yesterday’s baggage, it’s time to update your emotions. Release negativity and recognize going over out-of-date problems doesn’t serve you. Extract value from the past and live in the moment. Strengthen your focus on the present, too, and painful memories will fade leaving room for happier times.

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