In software engineering, the Proxy Design Pattern allows you to create a proxy object that acts as an intermediary between a client and a real object. The proxy object provides additional functionality such as controlling access to the real object or providing caching mechanisms. In this blog post, we will explore how to implement constructors for proxy patterns in C++.

Basic Proxy Pattern Structure

Before diving into the constructors, let’s briefly review the basic structure of the Proxy Pattern in C++. It typically involves three main components:

1. Real Subject: This is the actual object that the proxy object represents. It contains the underlying functionality that the client wants to access.
2. Proxy: The proxy object provides an interface to the client and controls access to the real subject. It holds a reference to the real subject and delegates the client’s requests to it.
3. Client: The client interacts with the proxy object instead of directly accessing the real subject.

Constructor Types for Proxy Patterns

Constructors in proxy patterns play a crucial role in creating and configuring the proxy object. Here are two common constructor types you can use:

1. Default Constructor

The default constructor creates a proxy object with default settings and initializes any necessary resources. It can be useful when you don’t have specific configuration requirements for the proxy object. Here’s an example:

class Proxy {
public:
    Proxy() {
        // Perform any necessary initialization here
        realSubject_ = new RealSubject();
    }

    // Proxy methods for client access
    // ...
    
private:
    RealSubject* realSubject_;
};

2. Constructor with Parameters

Sometimes, you may want to create a proxy object with specific configurations or pass additional parameters during construction. In such cases, you can define a constructor with parameters. Here’s an example:

class Proxy {
public:
    Proxy(int configurationOption) {
        // Perform initialization based on configurationOption
        realSubject_ = new RealSubject(configurationOption);
    }

    // Proxy methods for client access
    // ...
    
private:
    RealSubject* realSubject_;
};

In this example, the constructor takes an integer parameter configurationOption, which is used to configure the real subject object.

Conclusion

Constructors play an important role in creating and configuring proxy objects in the Proxy Pattern. Whether you use a default constructor or a constructor with parameters depends on your specific requirements. By understanding and implementing constructors in proxy patterns, you can effectively control access to real objects and enhance their functionality.

#proxy #cpp #programming #designpattern