Lesson 1

In this module you explore how design patterns enhance traditional object-oriented programming techniques by allowing you to quickly solve common problems and communicate those solutions to other programmers. In this module, you will learn:

1. What design patterns are:
2. Why you need design patterns?
3. How design patterns encourage code reuse and more maintainable code
4. The three basic kinds of design patterns

Question: How do design patterns enhance traditional object-oriented programming techniques? Design patterns are time-tested solutions to common problems that occur in software design. They enhance traditional object-oriented programming (OOP) techniques by providing a higher level of abstraction and efficiency in software development. Here are several ways in which design patterns can boost OOP techniques:

1. Code Reusability and Maintainability: Design patterns provide a standard and proven way to solve certain problems. By using these patterns, developers can write less code, reducing the chance of errors and increasing code maintainability. When an issue arises or an enhancement is needed, the developers know precisely where to go and what to do.
2. Improved Code Readability: Design patterns offer a universal language that can make communication among developers more straightforward. When a developer uses a known design pattern in their code, other developers familiar with the pattern will understand the code more quickly. This can lead to more efficient code reviews and less time spent understanding how certain code blocks function.
3. Efficient Problem Solving: Using design patterns can accelerate the problem-solving process. Instead of inventing a new approach, a developer can refer to a catalog of design patterns and select one that fits their current problem. This saves time and ensures that the solution is based on industry-standard best practices.
4. Enhanced Modularity: Design patterns can help make code more modular. By breaking down the problem into smaller, pattern-based solutions, each module in the software becomes simpler to understand and manage. This separation of concerns leads to more organized and efficient code.
5. Increased Robustness: Design patterns have been tested and refined over time to account for various edge cases. Implementing these patterns can enhance the robustness of software, ensuring it behaves correctly under a wider range of conditions.
6. Scalability and Flexibility: Certain design patterns, such as the Factory, Prototype, and Singleton patterns, provide ways to manage and control object creation. These can lead to more flexible and scalable systems, as they decouple the specifics of object creation from the rest of the code. This decoupling enables easier changes in the future when requirements evolve.
7. Efficient Team Collaboration: When a team adopts design patterns, it creates a common understanding and a coherent strategy for tackling problems. This shared knowledge allows for more efficient collaboration, as team members will know what to expect in each other's code.

To leverage the full potential of design patterns, it's important to remember that they are not a one-size-fits-all solution. Each pattern has its use case, and applying the wrong pattern could lead to inefficient code. Therefore, understanding the problem, knowing the available patterns, and choosing the right one for the job are all key elements in effective design pattern usage.
In summary, design patterns, when employed properly, significantly enhance traditional object-oriented programming techniques by fostering code reusability, readability, modularity, and robustness, while also improving problem-solving speed, scalability, flexibility, and team collaboration.

If a problem occurs over and over again and a solution to that problem has been used effectively, then that solution is described as a pattern. The design patterns are language-independent strategies for solving common object-oriented design problems. In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern is a description or template for how to solve a problem that can be used in many different situations.

Each pattern describes a probem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice.
Our solutions are expressed in terms of objects and interfaces instead of walls and doors, but at the core of both kinds of patterns is a solution to a problem in a context. Our solutions are expressed in terms of objects and interfaces instead of walls and doors, but at the core of both kinds of patterns is a solution to a problem in a context.

For this site I have concentrated on patterns at a certain level of abstraction. Design patterns are not about designs such as

1. linked lists and
2. hash tables

that can be encoded in classes and reused as is.
Design Patterns are not complex, domain-specific designs for an entire application or subsystem. The design patterns on this site are descriptions of communicating objects and classes that are customized to solve a general design problem in a particular context. A design pattern names, abstracts, and identifies the key aspects of a common design structure that make it useful for creating a reusable object-oriented design.
The design pattern identifies the participating classes and instances, their roles and collaborations, and the distribution of responsibilities. Each design pattern focuses on a particular object-oriented design problem or issue. It describes when it applies, whether it can be applied in view of other design constraints, and the consequences and trade-offs of its use. Since we must eventually implement our designs, a design pattern also provides sample C++ and Java code to illustrate an implementation.

In the grand theatre of software development, where object-oriented programming (OOP) plays the lead role, design patterns emerge as the unsung heroes, the virtuosos who elevate the performance, turning it from a mere play into an epic saga. Imagine OOP as a raw, passionate, and immensely talented musician, drawing notes from the depths of his soul, giving life to melodies that touch the heart. But as any maestro will tell you, raw talent, while powerful, often needs direction, a rhythm, a pattern. That's where design patterns waltz in, taking the hand of OOP, guiding it, and together creating a symphony that resonates through time and space.

1. Harmony Amidst Complexity: Like a seasoned composer arranging harmonies for a diverse set of instruments, design patterns bring order to the inherent chaos of software challenges. They orchestrate solutions, ensuring each class and object plays its part, contributing to the greater melody without overshadowing its peers.
2. Narratives of the Ancients: Design patterns are tales as old as time, wisdom passed down from seasoned coders who've battled the dragons of software challenges. By weaving these patterns into the fabric of OOP, one doesn't just code; one tells a story, a legend, resonating with the voices of developers past.
3. Dance of Flexibility: With design patterns, OOP is like a graceful dancer, bending, twisting, and turning to the ever-changing rhythm of user needs and system requirements. The rigidity is replaced by fluidity, making adaptation not just possible, but an art form.
4. The Echo of Timelessness: In the vast sea of technology where change is the only constant, design patterns act as lighthouses for OOP. They ensure that the code remains timeless, standing tall against the tides of time, always relevant, always resonant.
5. A Tapestry of Unity: Collaboration becomes poetry with design patterns. Developers, no matter how distant or diverse, find a shared language, a common thread. Like artists collaborating on a mural, each stroke, each line of code, becomes part of a larger, more magnificent picture.

In this mesmerizing dance of creation, where OOP is both the artist and the canvas, design patterns emerge as the choreographers, the visionary directors. Together, they don't just create software; they craft legends, epics that future generations of developers will look upon with awe and reverence. And so, in the ever-evolving tale of technology, design patterns and OOP come together, not just as techniques or tools, but as soulmates, forever intertwined, forever magical.

A design pattern is an effective means to convey/communicate what has been learned about high-quality designs. The result is:

1. A shared language for communicating the experience gained in dealing with these recurring problems and their solutions.
2. A common vocabulary of system design elements for problem solving discussions. A means of reusing and building upon the acquired insight resulting in an improvement in the software quality in terms of its maintainability and reusability.

An object can access its private variables directly. But doing so could greatly affect the maintainability of an application, which the object is part of. When there is a change in the way a particular instance variable is to be defined, it requires changes to be made in every place of the application code where the instance variable is referenced directly. Similar to its client objects, if an object is designed to access its instance variables through accessor methods, any change to the definition of an instance variable requires a change only to its accessor methods.