Design patterns are essential tools in software development that help developers create scalable and maintainable code. One such pattern is the Proxy pattern, which serves as a surrogate or placeholder for another object. This article will explore the Proxy design pattern in Ruby, discussing its purpose, types, and implementation with practical examples.
The Proxy pattern provides a way to control access to an object. It acts as an intermediary, allowing you to perform actions on the actual object while adding additional features such as lazy loading, access control, logging, or caching. The Proxy pattern can be particularly useful in scenarios where the actual object is resource-intensive or requires specific access controls.
There are several types of proxies, each serving different purposes:
Let’s explore how to implement the Proxy pattern in Ruby with a focus on the Virtual Proxy. We will create a simple example where a Proxy object controls access to a resource-intensive object.
First, we need to define the real subject class, which represents the object that the proxy will control access to. In this example, we will create a class called Image
that simulates loading an image from disk.
class Image def initialize(filename) @filename = filename load_image end def load_image puts "Loading image from #{@filename}..." sleep(2) # Simulate a time-consuming operation puts "Image loaded." end def display puts "Displaying #{@filename}." end end
The Image
class has a constructor that takes a filename, simulates loading the image, and has a method to display the image.
Next, we will create the Proxy class, which will control access to the Image
object. The proxy will defer the loading of the actual image until the display
method is called.
class ImageProxy def initialize(filename) @filename = filename @image = nil end def display load_image if @image.nil? @image.display end private def load_image @image = Image.new(@filename) end end
The ImageProxy
class initializes with a filename but does not load the image immediately. Instead, it loads the image only when the display
method is called for the first time.
Now that we have both the Image
and ImageProxy
classes, we can see how the proxy works in action.
proxy = ImageProxy.new("example_image.jpg") proxy.display # This will load the image proxy.display # This will use the already loaded image
When you run the code above, the first call to display
will load the image, while the second call will simply display it without reloading.
The Proxy pattern offers several advantages:
The Proxy pattern is widely used in various applications. Here are some common scenarios:
The Proxy design pattern is a powerful tool in Ruby that allows developers to control access to objects while adding additional functionality. By implementing a proxy, you can achieve lazy loading, access control, logging, and performance optimization. Understanding and utilizing design patterns like the Proxy pattern can lead to cleaner, more maintainable code and improved application performance.
As you continue to explore design patterns in Ruby, consider how you can apply the Proxy pattern in your projects. Whether you are working on a simple application or a complex system, the Proxy pattern can provide valuable benefits that enhance your code's efficiency and maintainability.
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