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Removed trailing whitespaces.

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Florian Wolters
2013-03-13 15:52:19 +01:00
parent f978c2e887
commit 7d91e9cd07
1 changed files with 8 additions and 8 deletions
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pages/Design-Patterns.md
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@@ -64,11 +64,11 @@ yourself a lot of trouble down the road by using factories.
## Singleton
When designing web applications, it often makes sense conceptually and architecturally to allow access to one and
When designing web applications, it often makes sense conceptually and architecturally to allow access to one and
only one instance of a particular class. The singleton pattern enables us to do this.
{% highlight php %}
<?php
<?php
class Singleton
{
static $instance;
@@ -93,16 +93,16 @@ $instance2 = Singleton::getInstance();
echo $instance1 === $instance2; // outputs 1
{% endhighlight %}
The code above implements the singleton pattern using a statically scoped variable and the `getInstance()` method.
The code above implements the singleton pattern using a statically scoped variable and the `getInstance()` method.
Note that the constructor is declared as private to prevent instantiation outside of the class via `new` keyword.
The singleton pattern is useful when we need to make sure we only have a single instance of a class for the entire
request lifecycle in a web application. This typically occurs when we have global objects (such as a Configuration
The singleton pattern is useful when we need to make sure we only have a single instance of a class for the entire
request lifecycle in a web application. This typically occurs when we have global objects (such as a Configuration
class) or a shared resource (such as an event queue).
You should be wary when using the singleton pattern, as by its very nature it introduces global state into your
application, reducing testability. In most cases, dependency injection can (and should) be used in place of a
singleton class. Using dependency injection means that we do not introduce unnecessary coupling into the design of our
You should be wary when using the singleton pattern, as by its very nature it introduces global state into your
application, reducing testability. In most cases, dependency injection can (and should) be used in place of a
singleton class. Using dependency injection means that we do not introduce unnecessary coupling into the design of our
application, as the object using the shared or global resource requires no knowledge of a concretely defined class.
* [Singleton pattern on Wikipedia](https://en.wikipedia.org/wiki/Singleton_pattern)