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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type"
content="text/html;charset=utf-8" />
<title>From STUPID to SOLID code!</title>
<link rel="stylesheet" href="reveal.js/css/reveal.min.css">
<link rel="stylesheet" href="reveal.js/css/theme/solarized.css" id="theme">
<link rel="stylesheet" href="reveal.js/lib/css/zenburn.css">
<link rel="stylesheet" href="css/custom.css">
<script>
document.write('<link rel="stylesheet" href="reveal.js/css/print/' +
(window.location.search.match(/print-pdf/gi) ? 'pdf' : 'paper') +
'.css" type="text/css" media="print">'
);
</script>
</head>
<body>
<div class="reveal">
<div class="slides">
<section>
<h1 class="title">Be <strong>pragmatic</strong> while <strong>coding</strong></h1>
<em>Ahmed SIOUANI</em>
</section>
<!-- Orthogonality -->
<section>
<section data-markdown>
<script type="text/template">
# Orthogonality
</script>
</section>
<section data-markdown>
<script type="text/template">
# In mathematics
* It is a relation of two lines at right angles to one another (perpendicularity) - Wikipedia
* An unchanged projection of any motion through one axe(X) to the other axe(Y).
</script>
</section>
<section data-markdown>
<script type="text/template">
<h1>Notion of <strong>independence</strong></h1>
</script>
</section>
<section data-markdown>
<script type="text/template">
# In programming
* Orthogonality = Independence, decoupling
<br><br>
* Things that are not related conceptually should not be related in the system.
<br><br>
<strong>Exemple</strong>:<br>
Database / User Interface
</script>
</section>
<section data-markdown>
<script type="text/template">
### Which class belongs to a perfectly orthogonal system?
<pre>
class Explode1 {
public explode1(InputStreamReader input)
public void readNextLine() throws IOException
public int numFields()
public String getField(int fieldNo)
}
</pre>
<br>
<pre>
class Explode2 {
public explode2(String line)
public int numFields()
public String getField(int fieldNo)
}
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Advantages
* Local fixes.
* Testability.
* Reusability.
</script>
</section>
</section>
<!-- Law of Demeter -->
<section>
<section data-markdown>
<script type="text/template">
# The Law of Demeter, LoD - 1987
### Principle of least knowledge
</script>
</section>
<section data-markdown>
<script type="text/template">
###The Law of Demeter
* A design guideline.
<br><br>
### Principles
* Each element should only talk to its friends, don't talk to strangers.
* Each element should have only limited knowledge about other elements: only elements "closely" related to the current element.
</script>
</section>
<section data-markdown>
<script type="text/template">
###Law of Demeter for Functions/Methods - (LoD-F)
Any method of a given object may only invokes the:
* Object itself
* Method's parameters
* Any objects created/instantiated within the method
* The object's direct component objects
* A global variable, accessible by the object, in the scope of the method.
</script>
</section>
<section data-markdown>
<script type="text/template">
###The Law of Demeter for Functions/Methods - (LoD-F)
<pre>
$this
->getFirstObject()
->doSomething(...);
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
###The Law of Demeter for Functions/Methods - (LoD-F)
<br>
Violation of the Demeter Law,
<pre>
$this
->getFirstObject()
->getSecondObject()
->doSomething();
</pre>
<br>
Encapsulation
<pre>
$this
->getFirstObject()
->doSomethingWithSecondObject()
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
###Advantages
* Adaptability and maintenability of your code.
<br><br>
###Drawbacks
* A systematic need of wrapping your calls.
</script>
</section>
</section>
<!-- Dependency Injection -->
<section>
<section data-markdown>
<script type="text/template">
# Dependency Injection
</script>
</section>
<section data-markdown class="highlighted-list">
<script type="text/template">
## Good to know!
* Do not confuse **"Dependecy Injection"**, **Inversion of Control** (IoC) and **Service Locator** (SL)
</script>
</section>
<section data-markdown>
<script type="text/template">
## Some definitions,
* <strong>Inversion of control, </strong>
- The relationship between higher lever class and detail classes
- Higher level classes shouldn't depend on detail classes, but rather the contrary
- Higher level classes should depend on abstraction (like interfaces)
* <Strong>Dependency Injection, </Strong>
- A dependency is an object used by your class
- An injection is the fact of passing an argyment to a function
* <Strong>Service Locator, </Strong>
- A container of service injected as a dependency.
- <strong>In Symfony, </strong>injection of the DIC.
</script>
</section>
<section data-markdown>
<script type="text/template">
## Dependency Injection
<strong>Injection via the setter, </strong>
<pre>
public function setMailer(Mailer $mailer)
{
$this->mailer = $mailer;
}
</pre>
<strong>Access via the getter,,</strong>
<pre>
public function getMailer()
{
return $this->mailer;
}
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Wrong !
* <strong>Runtime Error,</strong> in case your setter isn't called before.
* The appropriate getter,
<pre>
private function getMailer()
{
if (!($this->mailer instanceof Mailer)) {
throw new \LogicException('The Mailer dependency is missing.');
}
return $this->mailer;
}
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
* Setter Injection</strong>
- Should be used only when you're not allowed to access the object construction.
- For classes that extends third-party libraries.
* <strong>Example:</strong>
- A doctrine repository is accessible only via the <strong>EntityManager</strong>. You don't have control over its construction. For this specific case, injection is performed via setters.
</script>
</section>
<section data-markdown>
<script type="text/template">
#Example
<div style="height:20px;width:20px;background-color:red;float:right;"></div>
<pre>
first_service_id:
class: %first_service.class%
calls:
- [ setAnyOtherService, [@any_other_service_id]]
</pre>
<div style="height:20px;width:20px;background-color:green;float:right;"></div>
<pre>
second_service_id:
class: %second_service.class%
arguments: [@any_other_service_id]
</pre>
</script>
</section>
</section>
<!-- Exceptions -->
<section>
<section data-markdown>
<script type="text/template">
# Exceptions
</script>
</section>
<section data-markdown>
<script type="text/template">
</script>
</section>
<section data-markdown>
<script type="text/template">
Only use exceptions for <strong>Exceptional</strong> problems
</script>
</section>
<section data-markdown>
<script type="text/template">
* File opening,
<pre>
public void open_file() throws FileNotFoundException {
$stream = new FileInputStream("/etc/passwd");
}
</pre>
<pre>
public void open_file() throws FileNotFoundException {
$stream = new FileInputStream("/home/userX/test_results.xml");
}
</pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
* Error handlers
<pre>
public void open_file() {
File f = new File("/home/userX/test_results.xml");
if (!f.exists()) {
return false;
}
$stream = new FileInputStream(f);
return true;
}
</pre>
* open an inexistant file => conventional error
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## **STUPID** Code
</script>
</section>
<section data-markdown class="highlighted-list">
<script type="text/template">
## **STUPID** Code?
* **S**ingleton
* **T**ight Coupling
* **U**ntestability
* **P**remature Optimization
* **I**ndescriptive Naming
* **D**uplication
</script>
</section>
<section data-markdown>
<script type="text/template">
## **S**ingleton
* Not extensible (configuration limits)
* Introduce strong couplings
* Untestability
</script>
</section>
<section data-markdown>
<script type="text/template">
## **T**ight Coupling
Generalisation of the limits introduced by the "Signleton" Anti-pattern.
</script>
</section>
<section data-markdown>
<script type="text/template">
## **U**ntestability
</script>
</section>
<section data-markdown>
<script type="text/template">
## **P**remature Optimization
_Premature optimization is the root of all evil._ — Donald Knuth.
</script>
</section>
<section data-markdown>
<script type="text/template">
## **I**ndescriptive Naming
* Meaningless naming.
* Do not use abbreviations.
</script>
</section>
<section data-markdown>
<script type="text/template">
## **D**uplication
**D**on't **R**epeat **Y**ourself!
**K**eep **I**t **S**imple, **S**tupid!
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## **SOLID** to the rescue!
</script>
</section>
<section data-markdown class="highlighted-list">
<script type="text/template">
## **S**OLID
* **S**ingle Responsability Principle
* **O**pen Close Principle
* **L**iskov Substitution Principle
* **I**nterface Segregation Principle
* **D**ependency Injection Principle
</script>
</section>
<section data-markdown>
<script type="text/template">
## **S**ingle Responsibility Principle (SRP)
There should **never** be **more than one reason**
<br>for a class to change.
</script>
</section>
<section>
<img src="images/srp.jpg" />
<p>Just because you can, doesn't mean you should!</p>
</section>
<section data-markdown>
<script type="text/template">
## **O**pen/Closed Principle (OCP)
* you should be able to extend a classes brehavior, without modifying it - Robert C.Martin
</script>
</section>
<section data-markdown>
<script type="text/template">
## **L**iskov Substitution Principle (LSP)
Derived classes must be substituable for their base classes - Robert C.Martin
<br><br>
* <strong>Be careful</strong>, when setting returned values in weakly-typed languages.
</script>
</section>
<section data-markdown>
<script type="text/template">
## **I**nterface Segregation Principle (ISP)
Make fine grained interfaces that are client specific - Robert C.Martin
</script>
</section>
<section data-markdown>
<script type="text/template">
## **D**ependency Injection Principle (DIP)
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
# Unit tests
</script>
</section>
<section data-markdown>
<script type="text/template">
##Test the states of your logic
Exemple :
<pre>
int function_1(int a, int b) {
return a / (a + b)
}
</pre>
<br>
<pre>
testFunction_1() {
assertEqual(0.5, function_1(1,1));
}
</pre>
Code coverage 100% / State coverage: 50%
</script>
</section>
</section>
<section data-markdown>
<script type="text/template">
## Thank you, Questions?
<br>
<ul class="me">
<li><a href="http://ahsio.com" title="website">ahsio.com</a></li>
</ul>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Credits
* <a href="http://en.wikipedia.org/wiki/Andy_Hunt_(author)">Andrew Hunt</a>
* <a href="http://en.wikipedia.org/wiki/Dave_Thomas_(programmer)">David Thomas</a>
* <a href="http://lostechies.com/derickbailey/">Derick Bailey</a>
* <a href="http://williamdurand.fr/">William Durand</a>
* <a href="https://twitter.com/hhamon">Hugo Hamon</a>
* <a href="http://gnugat.github.io">Loïc Chardonnet</a>
</script>
</section>
</div>
</div>
<script type="text/javascript" src="reveal.js/lib/js/head.min.js"></script>
<script type="text/javascript" src="reveal.js/js/reveal.min.js"></script>
<script type="text/javascript">
Reveal.initialize({
controls: true,
progress: true,
history: true,
center: true,
theme: Reveal.getQueryHash().theme,
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// Optional libraries used to extend on reveal.js
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{ src: 'reveal.js/plugin/markdown/marked.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
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</html>