The Adapter pattern is a structural design pattern that enables objects with incompatible interfaces to collaborate seamlessly.
![](/images/adapter-problem.png)

## Implementing Adapter

To overcome the incompatibility issue, you can create an adapter. The adapter acts as a special object that converts the interface of one object into a format understandable by another object.


![](/images/adapter-solution.png)


## Structure of the Adapter Pattern
![](/images/adapter-structure.png)
The Adapter pattern comprises the following components:

1.  **Client**: This class contains the existing business logic of the program.
    
2.  **Client Interface**: The Client Interface describes a protocol that other classes must follow to collaborate with the client code.
    
3.  **Service**: This is a useful class, usually a 3rd-party or legacy component. The client cannot use this class directly due to its incompatible interface.
    
4.  **Adapter**: The Adapter is a class that can work with both the client and the service. It implements the client interface while wrapping the service object. The adapter receives calls from the client via the adapter interface and translates them into calls to the wrapped service object in a format it can understand.
    

## Conclusion

The Adapter pattern is a valuable tool for bridging incompatible interfaces, allowing different components to work together harmoniously. By using adapters, you can integrate new functionalities and third-party libraries into your application without disrupting the existing codebase.

Adapter Pattern: Bridging Incompatible Interfaces

The Abstract Factory pattern provides an interface to create families of related objects without specifying their concrete classes.

## Key Components of the Abstract Factory Pattern

![](/images/abstract-factory-structure.png)

1.  **Abstract Products**: Abstract Products declare interfaces for a group of distinct but related products that form a product family. Each abstract product represents a specific type of object, such as a chair or a sofa.

2.  **Concrete Products**: Concrete Products are distinct implementations of abstract products, grouped by variants. Each abstract product (e.g., chair or sofa) must be implemented in all given variants (e.g., Victorian or Modern).

3.  **Abstract Factory Interface**: The Abstract Factory interface declares a set of methods to create each of the abstract products. This interface allows you to create different types of products without exposing their concrete implementations.
    
4.  **Concrete Factories**: Concrete Factories implement methods for creating the abstract products declared in the Abstract Factory interface. Each concrete factory represents a specific family of products, such as the Victorian furniture family or the Modern furniture family.
    

## Example: Cross-Platform Application

![](/images/abstract-factory.png)

To illustrate the Abstract Factory pattern, imagine a cross-platform application that needs to support multiple operating systems. The application requires the creation of various UI components, such as buttons, menus, and text fields, which may have different implementations for each platform.

## Conclusion

The Abstract Factory pattern is a powerful creational design pattern that allows you to create families of related objects without specifying their concrete classes. By defining abstract product interfaces and concrete product implementations in separate factories, the pattern facilitates the construction of complex object families in a flexible and extensible manner.

In our cross-platform application example, the Abstract Factory pattern would enable you to create UI components for different operating systems without tightly coupling the application code to specific platform implementations. By adopting the Abstract Factory pattern, you can achieve a high level of modularity and adaptability in your software, making it easier to support different product families with minimal code changes.

Abstract Factory Pattern: Creating Family of Objects

In the world of structural patterns, the Bridge pattern offers an elegant solution for constructing larger and more flexible structures while maintaining efficiency.

The Bridge pattern allows us to create an easy way to add features to a low-level implementation. It is composed of an implementation that handles the "low-level" work and an abstraction that deals with the "high-level" work. The abstraction extends or refines the implementation, adding new features to it.

## Understanding the Bridge Pattern

At its core, the Bridge pattern separates the interface and implementation of a class, enabling them to vary independently. This decoupling allows us to combine different abstractions with different implementations dynamically.

## Class Diagram

The class diagram of the Bridge pattern demonstrates the relationships between the key components: the abstraction, the implementation, and their derived classes.

![](/images/bridge-structure.png)

## Example: Building a TV with Remote Control

Suppose we want to create a TV with a remote control. The Bridge pattern can act as a "link" between the two components, separating the TV's low-level implementation from the remote control's high-level features.

![](/images/bridge-example.png)

## Implementation Details

The Bridge pattern involves the following elements:

-   **Abstraction**: This represents the high-level interface and is responsible for defining the abstract methods and properties.
    
-   **Implementation**: This represents the low-level interface, implementing the methods defined in the abstraction.
    
-   **Derived Classes**: The abstraction and implementation classes can have derived classes that extend or refine their functionalities.
    

## Benefits of the Bridge Pattern

The Bridge pattern offers several advantages:

-   **Flexibility**: It allows us to combine different abstractions with different implementations dynamically, providing high flexibility in the system.
    
-   **Decoupling**: By separating the interface and implementation, the Bridge pattern reduces tight coupling between classes, making the code more maintainable and scalable.
    
-   **Reusability**: Both the abstraction and implementation classes can be extended independently, promoting code reuse.
    

## Conclusion

The Bridge pattern is a powerful tool for building flexible and efficient abstractions in a structured manner. By decoupling the interface and implementation, the pattern enables seamless combination and modification of components, leading to more maintainable and adaptable systems.

In the example of creating a TV with a remote control, the Bridge pattern showcases its ability to link different components while allowing easy extension of their functionalities. By leveraging the Bridge pattern, developers can construct versatile systems that efficiently handle the complexity of different abstractions and implementations.

Bridge Pattern: Building Flexible and Efficient Abstractions

The Builder pattern is a creational design pattern that facilitates the construction of complex objects in a step-by-step manner. It also helps eliminate the need for telescoping constructors, making the object creation process more flexible and manageable.

## Key Components of the Builder Pattern
![](/images/builder-structure.png)
1.  **Builder Interface**: The Builder interface declares the product construction steps that are common to all types of builders. Each builder provides different implementations of these construction steps, offering the manager various ways of building the product.
    
2.  **Concrete Builders**: Concrete Builders provide different implementations of the construction steps defined in the Builder interface. They may produce products that do not necessarily follow a common interface or belong to the same class hierarchy.
    
3.  **Products**: Products are the resulting objects that get constructed by different builders. These products can have various structures and features, depending on the concrete builder used.
    
4.  **Director**: The Director class defines the order in which to call construction steps, enabling the creation and reuse of specific configurations of products. It orchestrates the building process using a builder, allowing the client to create complex objects without knowing the details of the construction steps.
    
5.  **Client**: The Client associates one of the builder objects with the director. Usually, this association is established via parameters of the director's constructor. The director then uses that builder object for all further constructions. Alternatively, the client can pass the builder object to the director's production method, allowing for the use of different builders for different product configurations.
    

## Example: Cross-Platform Application

To demonstrate the Builder pattern, consider a cross-platform application that can be built for various operating systems. The application has different components like a user interface, database, and networking, which can vary depending on the target platform.

## Conclusion

The Builder pattern is a powerful creational design pattern that enables you to construct complex objects step by step. By using separate builders to create different product configurations and a director to manage the construction process, the pattern allows you to build flexible and customizable objects without complex constructors.

In our cross-platform application example, the Builder pattern would enable you to create tailored versions of the application for different operating systems while maintaining a clean and extensible codebase. By embracing the Builder pattern, you can achieve a more modular and maintainable approach to object construction in your software projects.

Builder Pattern: Constructing Complex Objects Step by Step

# Chain of responsability pattern

 __Avoid coupling the sender of a request to its receiver by giving more than one object the chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.__

## Where and When Chain of Responsibility pattern is applicable ?

-   When you want to decouple a request’s sender and receiver
-   Multiple objects, determined at runtime, are candidates to handle a request
-   When you don’t want to specify handlers explicitly in your code
-   When you want to issue a request to one of several objects without specifying the receiver explicitly.

### Class Diagram

![](/images/chain-structure.gif)

### Example

![](/images/chain-example.png)


[school request example](https://stackblitz.com/edit/typescript-fktrnv?file=index.ts)

Chain of responsability pattern

## Composite Pattern: Building Tree-like Structures

The Composite pattern is akin to a tree structure, comprising containers and leaves. The containers, also known as composites, can hold leaves or other composites, but a leaf is the terminal component at its level and cannot contain further elements.

## Understanding the Composite Pattern

In a Composite pattern, a container doesn't have knowledge of the concrete classes of its children. Instead, it interacts with all sub-elements through the common component interface. The container delegates work to its sub-elements, processes intermediate results, and returns the final result to the client.

On the other hand, a leaf is a basic element with no sub-elements and implements the component interface.

## Structure of the Composite Pattern

The Composite pattern consists of the following components:

1.  **Component Interface**: This is an interface that declares methods to interact with both containers and leaves.
    
2.  **Composite (Container)**: Containers implement the component interface and can hold other components, either leaves or other composites.
    
3.  **Leaf**: Leaves implement the component interface and represent basic elements with no sub-elements.


![](/images/composite-leaf.png)


## Implementing the Composite Pattern

To implement the Composite pattern, identify the different components in the tree structure. All components must implement the Component interface and delegate the work to the leaves.

## Example: DOM Tree

A common real-world example of the Composite pattern is the Document Object Model (DOM) used in web development. In the DOM, HTML elements form a hierarchical tree structure. HTML elements like `div`, `span`, and `p` act as containers that can contain other elements (both containers and leaves) like `img`, `a`, and text nodes. The DOM tree provides a unified interface to interact with all elements, making it easy to manipulate and traverse the entire document.

## Real-World Example

Imagine building a file system that includes directories (containers) and files (leaves). The directories can hold files and other directories. The Composite pattern allows you to treat both directories and files uniformly, making it easy to perform operations on the entire file system tree.

## Benefits of the Composite Pattern

The Composite pattern offers several advantages:

-   **Hierarchical Structure**: It simplifies working with hierarchical structures by treating containers and leaves uniformly.
-   **Flexibility**: New elements can be added to the tree structure without affecting the existing code.
-   **Code Reuse**: The component interface promotes reusability of code and ensures consistency in interactions.

## Conclusion

The Composite pattern is a powerful design pattern for creating tree-like structures with containers and leaves. By providing a consistent interface for all elements, it enables seamless manipulation and traversal of complex hierarchies.

![](/images/dom.png)

In real-world examples like the DOM and file systems, the Composite pattern proves its versatility and effectiveness in managing hierarchical structures. By using this pattern, developers can build maintainable and flexible systems that scale effortlessly as new components are introduced.

Composite Pattern: Building Tree-like Structures

The Decorator pattern allows you to dynamically add extra behaviors to objects at runtime without altering the existing code that uses these objects. It provides a flexible and maintainable way to extend the functionality of objects without resorting to excessive inheritance.

## Understanding the Decorator Pattern

When faced with a scenario where traditional inheritance might lead to a class explosion or tightly coupled classes, the Decorator pattern comes to the rescue. It follows the principle of composition over inheritance, where objects can be decorated with additional functionalities by aggregating or composing them at runtime.

![](/images/decorator-diagram.png)

## Class Diagram

A class diagram is a visual representation that describes how classes are related to each other in an application. It is a crucial tool in understanding and depicting different design patterns. Before we delve into the world of design patterns, let's take a moment to familiarize ourselves with class diagrams.

![](/images/decorator-structure.png)

## Example Use Case

Consider a gasoline-powered car that we want to equip with nitro to enhance its performance. Since a car is typically a "final" product, extending the car class directly is not a feasible option. Instead, we can use the Decorator pattern to add customization without modifying the original car class. By creating a wrapper or a decorator, we can inject the nitro functionality at runtime.

![](/images/decorator-example.png)

## Implementation Details

The Decorator pattern allows objects to delegate tasks to another linked "helper" object, or in some cases, multiple objects. This way, we can easily substitute or combine different behaviors, changing the object's behavior at runtime.

## Benefits of the Decorator Pattern

The Decorator pattern brings several advantages to the table:

-   **Dynamic Behavior**: With the Decorator pattern, you can easily modify an object's behavior by adding or removing decorators at runtime.
-   **Maintainable Code**: It promotes composition over inheritance, resulting in a more maintainable and extensible codebase.
-   **Reusable Components**: Decorators can be reused and combined in various ways to create different combinations of behaviors.

## Conclusion

The Decorator pattern is a valuable design pattern for adding flexible behaviors to objects at runtime. By embracing composition and delegation, it allows for dynamic customization without the need for excessive inheritance or modification of existing code.

In our example, injecting nitro into the car's engine showcased how the Decorator pattern can enhance the capabilities of an object while keeping the codebase clean and maintainable.

For a practical implementation of the Decorator pattern, you can explore the provided [GitHub example](https://github.com/igloar96/byli-decorator), which demonstrates how to extend objects with decorators to achieve desired functionalities.

Decorator Pattern: Adding Flexible Behaviors to Objects

The Facade design pattern is a structural pattern that offers a simplified interface to a complex system, library, or framework. It acts as a unified interface, concealing the inner workings of a cumbersome or intricate subsystem, which we might prefer to keep hidden from the outside world.

The beauty of this pattern lies in its simplicity. It provides an elegant interface that shields users from the complexity lurking beneath the surface, making it easier to interact with the system.

## Understanding the Facade Pattern

Imagine a scenario where a software application relies on a complex set of classes and subsystems to achieve its functionality. Navigating through the intricacies of this system can be overwhelming and cumbersome. The Facade pattern steps in and offers a straightforward, user-friendly interface, allowing clients to interact with the system without delving into its inner complexities.

## Key Characteristics of the Facade Pattern

1.  **Facade**: This is the core component of the pattern. The facade acts as a mediator between the client and the underlying subsystem. It provides a unified interface that simplifies the interaction with the system.
    
2.  **Complex Subsystem**: The complex subsystem contains multiple classes and components, which may be interconnected and interdependent.
    

## Example Use Case

Let's consider an example where a computer's startup process involves several complicated steps, such as loading drivers, initializing hardware components, and starting the operating system. Instead of exposing these intricate details to the user, a startup facade can be implemented. The facade encapsulates the entire startup process and provides a single method, such as "startComputer," to initiate the boot sequence. This shields the user from the complexities involved and offers a straightforward way to start the computer.

## Benefits of the Facade Pattern

The Facade pattern brings several advantages to software development:

-   **Simplified Interface**: The pattern presents a user-friendly interface that shields clients from complex subsystem interactions.
-   **Decoupling**: By using a facade, clients don't need to directly interact with multiple classes within the subsystem, reducing coupling and promoting better maintainability.
-   **Abstraction**: The facade abstracts away the intricate implementation details, allowing for easier changes in the future.

## Structure
![](/images/facade-structure.png)

## Example
![](/images/facade-example.png)
## Conclusion

The Facade design pattern elegantly addresses the challenges of dealing with complex systems by providing a clean and straightforward interface. By hiding the "dark side" of a subsystem, the pattern promotes encapsulation and simplifies interactions, resulting in cleaner and more maintainable code.

As developers, we should embrace the power of the Facade pattern when dealing with intricate systems. By offering a simple facade to the outside world, we can make our software more approachable, easier to maintain, and ultimately, a joy to work with.

Facade Pattern: Simplifying Complex Systems

The Factory Method pattern is a creational design pattern that provides a way to create objects without knowing their exact dependencies and types in advance. Instead of using the "new" operator directly, this pattern encapsulates the object creation process in a method called the factory method.

## Key Components of the Factory Method Pattern

![](/images/factory.png)

1.  **Product Interface**: Make all products follow the same interface. This interface should declare methods that make sense in all products. By adhering to a common interface, the products can be treated uniformly in the client code.
    
2.  **Concrete Products**: Implement the products that meet all the interface methods with consistency. Each concrete product represents a specific implementation of the product interface.
    
3.  **Creator Class**: The Creator class declares the factory method, which returns the interface common to all concrete products. It may or may not be an abstract class. The Creator class encapsulates the object creation and ensures that the client code remains decoupled from the concrete product implementations.
    
4.  **Concrete Creators**: Concrete Creators are subclasses of the Creator class responsible for instantiating the related concrete product. They override the factory method to return specific concrete products.
    


## Conclusion

The Factory Method pattern is a versatile creational design pattern that allows you to create objects without specifying their exact types in advance. By encapsulating the object creation process in a factory method, the pattern promotes loose coupling and flexibility in the client code.

In our cross-platform application example, the Factory Method pattern enables the creation of different buttons for different operating systems, abstracting away the details of button instantiation from the client code. By applying the Factory Method pattern, you can build more maintainable and adaptable systems that can create objects dynamically based on runtime requirements.

Factory Method Pattern: Creating Objects Without Knowing Exact Types

The Flyweight design pattern is a structural pattern that aims to reduce memory usage and improve performance by efficiently sharing objects used in large quantities. It is particularly useful when an application needs to create a large number of similar objects with some shared intrinsic state.

## Understanding the Flyweight Pattern

At its core, the Flyweight pattern splits an object into intrinsic and extrinsic states. The intrinsic state represents shared data that remains constant across multiple objects, while the extrinsic state represents unique data specific to each object. By isolating the shared data in separate objects and reusing them, the Flyweight pattern significantly reduces memory consumption.

## Key Components of the Flyweight Pattern

1.  **Flyweight Interface**: This is an interface or abstract class that declares the method(s) for accessing and manipulating the intrinsic state shared among flyweight objects.
    
2.  **Concrete Flyweight**: These are the concrete implementations of the Flyweight interface, representing the shared intrinsic state. Instances of concrete flyweights are shared among multiple contexts (client objects).
    
3.  **Unshared Flyweight (Optional)**: In some cases, not all state can be shared. Unshared flyweights represent the intrinsic state that cannot be shared and should be managed separately.
    
4.  **Flyweight Factory**: This is a factory class responsible for creating and managing flyweight objects. It ensures that flyweight objects are properly shared and reused.
    

## Class Diagram

Below is the class diagram representing the structure of the Flyweight design pattern:

![Flyweight Class Diagram](/images/flyweight-structure.png)

In the class diagram, we can see the relationships between the key components of the Flyweight pattern. The client objects (Context) interact with the FlyweightFactory to obtain shared flyweight objects (ConcreteFlyweight) with the desired intrinsic state. The intrinsic state is then combined with the extrinsic state unique to each context, allowing the objects to behave as if they were fully instantiated instances, while minimizing memory overhead.

## Use Cases of the Flyweight Pattern

The Flyweight pattern is applicable in various scenarios, such as:

-   Text processing applications handling a large number of similar fonts or characters.
-   Graphics rendering applications dealing with many identical shapes or icons.
-   Game development for managing a vast number of game objects with shared attributes.

## Benefits of the Flyweight Pattern

By adopting the Flyweight pattern, applications can experience the following benefits:

-   **Memory Optimization**: The pattern reduces memory consumption by reusing shared intrinsic state among multiple objects.
-   **Performance Improvement**: Reduced memory overhead leads to improved performance and reduced processing time.
-   **Scalability**: The pattern enhances the application's scalability, allowing it to handle a large number of objects efficiently.

## Conclusion

The Flyweight design pattern is a valuable tool for optimizing memory usage and improving performance in applications that frequently use similar objects. By carefully managing shared intrinsic state, developers can achieve significant gains in memory efficiency and overall application responsiveness.

When implementing the Flyweight pattern, it is essential to identify which state can be shared and how to effectively manage shared objects. With proper utilization, the Flyweight pattern can be a powerful asset in creating high-performing and memory-efficient software systems.

Flyweight Pattern: Optimizing Memory Usage and Performance

The Prototype pattern is a creational design pattern that allows you to create new objects by copying existing ones.

## Key Components of the Prototype Pattern
![](/images/prototype-structure.jpg)
1.  **Prototype Interface**: The Prototype interface declares the cloning methods. In most cases, it consists of a single `clone` method.
    
2.  **Concrete Prototype Class**: Concrete Prototype classes implement the cloning method defined in the Prototype interface.
    
3.  **Concrete Subclasses**: Concrete subclasses also implement the Prototype interface, providing their specific implementation of the cloning method.
    
4.  **Client**: The client creates a prototype object using the `clone` method.
    

## Code Example

In Java and C#, the Prototype pattern is facilitated through the use of interfaces:

-   In Java, the `Cloneable` interface is used to enable object cloning. The class implementing `Cloneable` can be cloned using the `clone()` method, which returns a shallow copy of the object.
    
-   In C#, the `ICloneable` interface is used to support cloning. The `ICloneable` interface provides a `Clone()` method that creates a new instance of a class with the same value as an existing instance.
    

## Example Use Case

Consider a scenario where you have an object with a complex structure, and you want to create variations of this object. Instead of creating new objects from scratch, you can use the Prototype pattern to clone the existing object and modify it as needed. This approach saves resources and time, as you don't need to recreate the entire object hierarchy.

## Conclusion

The Prototype pattern is a useful creational design pattern that allows you to create new objects by copying existing ones. It helps reduce code duplication and simplifies the process of creating variations of complex objects. By using the Prototype pattern, you can enhance the efficiency and flexibility of object creation in your application.

Prototype Pattern: Creating New Objects via Cloning

## Motivation

The Proxy design pattern provides a surrogate or placeholder for another object, allowing us to control access to it. One key reason for using a proxy is to defer the full cost of creating and initializing an object until it's actually needed. For instance, in a document editor with graphical objects, some expensive objects like large raster images should be created only when required, not all at once during document opening, as not all objects may be visible simultaneously.

The solution lies in using an image proxy that serves as a stand-in for the actual image. The proxy behaves like the image and handles instantiation when needed.

When the document editor invokes the Draw operation, the image proxy creates the real image, and subsequent requests are directly forwarded to the image. The proxy keeps a reference to the image after creation to manage further interactions.



## Use Cases

The Proxy pattern is applicable whenever a more versatile or sophisticated reference to an object is required, beyond a simple pointer. Here are common situations where the Proxy pattern is beneficial:

1.  **Remote Proxy**: Responsible for encoding requests and arguments and sending them to the real subject in a different address space. Useful for remote communication scenarios.
    
2.  **Virtual Proxy**: Caches additional information about the real subject, postponing direct access until necessary. For instance, the ImageProxy from the Motivation caches the real image's extent.
    
3.  **Protection Proxy**: Controls access to the original object, providing different access rights. KernelProxies in operating systems offer protected access to operating system objects.

![](/images/proxy-example.png)

The image proxy creates the real image only when the document editor asks it to display itself by invoking its Draw operation. The proxy forwards subsequent requests directly to the image.It must therefore keep a referenceto the image after creating it.

### Use cases

Proxy is applicable whenever there  **is a need for a more versatile or sophisticated reference to an object than a simple pointer**. Here are several common situations in which the Proxy pattern is applicable:

-   A  **remote proxy**  are responsible for encoding a request and its arguments and for sending the encoded request to the real subject in a different address space.
-   A  **virtual proxy**  may cache additional information about the real subject so that they can postpone accessing it. For example, the ImageProxy from the Motivation caches the real image's extent.
-   A  **protection proxy** controls access to the original object. Protection proxies are useful when objects should have different access rights. For example KernelProxies in operating system's provides protected access to operating system objects.

### Structure
![](/images/proxy-structure.png)


### Example 
[Cool lazy loading proxy example](https://stackblitz.com/edit/typescript-umzfn2?file=index.ts)

Proxy Pattern : Controlling Object Access

The Singleton pattern is based on the idea of delivering a single instance of a class. It ensures that only one object of a class exists and provides a global point of access to that instance.

## The Need for Singleton

In certain situations, it is critical to guarantee that only one instance of a class exists. Consider a scenario where multiple printers are available, but there is only one pool responsible for handling printing tasks. In such cases, it becomes necessary to control the creation and access of the print manager object. This requirement is common in concurrent systems where access control to a single instance is crucial.
# Structure
![](/images/singleton-structure.png)


## Class Diagram with Private Constructor

In the class diagram, a private constructor restricts the direct instantiation of the class. The only way to obtain an instance is by calling a static method like `getInstance()` that provides the already created object or creates one if it doesn't exist.

## Thread Safety in Singleton

By default, a singleton class is not thread-safe. Multiple threads can access the singleton at the same time and create multiple instances, violating the singleton concept. **Therefore, it is essential to consider thread safety while implementing the Singleton pattern in a multithreaded environment.**

##  Example:  Database Connection Class

In this example, the database connection class acts as a Singleton. It has a private constructor, ensuring that no other objects can be created directly. Instead, a static method `getInstance()` is used to obtain the instance. This method caches the first created object and returns it in all subsequent calls, guaranteeing a single instance of the class.


## Conclusion

The Singleton pattern is a powerful tool to ensure that only one instance of a class exists throughout the application. It is commonly used in scenarios where resources need to be shared across the application or when you want to avoid creating multiple instances of a resource-heavy object.

When implementing a Singleton, it is crucial to consider thread safety, especially in concurrent environments. By choosing an appropriate thread-safe approach, you can create a robust and reliable Singleton that serves its purpose effectively.

Singleton Pattern: Ensuring a Single Instance

![](/images/design-patterns.png)

Design patterns are high-level solutions that provide answers to different problems that frequently occur in software development. They are well-established techniques that help in achieving flexibility, scalability, and code reuse in applications.

**First you need to read :**

*   [Four Pillars of Object-Oriented Programming (OOP)](/oop-pilars)
*   [Class Diagrams](/class-diagram)

## Why Use Design Patterns?

Design patterns promote flexible and scalable code, enabling a significant amount of code reuse. Using design patterns in your software development process can elevate your level of professionalism. Mentioning the name of a pattern can convey a well-known solution to a problem, saving time and effort in explaining the problem and its solution.

## Types of Design Patterns

Design patterns can be broadly classified into three types:

### 1. Creational Patterns

Creational patterns focus on object creation mechanisms, increasing flexibility and code reuse. They include patterns like:

*   Factory Method
*   Abstract Factory
*   Builder
*   Prototype
*   Singleton

### 2. Structural Patterns

Structural patterns assemble objects and classes into larger structures, maintaining flexibility and efficiency. Some of the structural patterns are:

*   Adapter
*   Bridge
*   Composite
*   Decorator
*   Facade
*   Flyweight
*   Proxy

### 3. Behavioral Patterns

Behavioral patterns deal with communication and assignment of responsibilities between objects. They include patterns like:

*   Chain of Responsibility
*   Command
*   Iterator
*   Mediator
*   Memento
*   Observer
*   State
*   Strategy
*   Template Method
*   Visitor

## Conclusion

Design patterns are essential tools in software development that offer solutions to recurring problems. Understanding the four pillars of OOP and familiarizing yourself with different types of design patterns will enable you to create more maintainable, flexible, and reusable code. Embracing design patterns can elevate your coding skills and enhance your overall professionalism as a software developer.
