Structural GOF

The Proxy Design Pattern is a structural pattern that provides a surrogate or placeholder for another object. It allows you to control access to the real object, providing additional functionality such as access control, lazy initialization, or logging. The proxy pattern involves creating a proxy class that implements the same interface as the real object and delegates requests to the real object. Components of the Proxy Design Pattern: Subject: An interface or abstract class that defines the common interface for both the RealSubject and the Proxy. RealSubject: The actual class that performs the real operations. Proxy: A class that implements the Subject interface and maintains a reference to the RealSubject. It controls access to the RealSubject and can add additional behavior. Simple Example: Let’s create a simple example where we use a Proxy to control access to a RealImage object. The RealImage class represents a large image that we want to load and display, but we’ll use a Proxy to manage access and load the image only when necessary. ...

The Flyweight Design Pattern is a structural pattern that optimizes memory usage by sharing common parts of objects to support a large number of similar objects efficiently. This pattern is used when you have a large number of objects with shared states and you want to minimize memory usage. Components of the Flyweight Design Pattern: Flyweight: An interface or abstract class that declares methods for managing and accessing extrinsic state. ConcreteFlyweight: Implements the Flyweight interface and defines the intrinsic state of the object. The intrinsic state is shared across all instances of the flyweight. FlyweightFactory: Manages the creation and reuse of Flyweight objects. It ensures that flyweights are shared properly. Client: Maintains references to flyweights and uses them. Simple Example: Let’s create a simple example where we manage a collection of Character objects in a text editor. Each character may have different formatting (e.g., bold or italic), but the characters themselves (e.g., ‘A’, ‘B’, ‘C’) are shared. ...

The Facade Design Pattern is a structural pattern that provides a simplified interface to a complex subsystem. It hides the complexity of the subsystem and makes it easier to use. The pattern involves creating a facade class that delegates requests to the appropriate components of the subsystem. Components of the Facade Design Pattern: Facade: The class that provides a simplified interface to the complex subsystem. Subsystem Classes: The classes that make up the complex subsystem. They handle the actual operations and functionality. Simple Example: Let’s create a simple example where we have a home theater system with several components. We will use the Facade Pattern to provide a simplified interface for turning on and off the home theater system. ...

The Decorator Design Pattern is a structural pattern that allows you to dynamically add behavior to an object without altering its structure. This pattern provides a flexible alternative to subclassing for extending functionality. Components of the Decorator Design Pattern: Component: The interface or abstract class defining the common interface for both the core object and decorators. ConcreteComponent: The class implementing the Component interface. This is the core object to which additional behaviors can be added. Decorator: An abstract class or interface that implements the Component interface and contains a reference to a Component object. It delegates operations to the Component and can add additional behavior. ConcreteDecorator: A class extending the Decorator that adds specific behavior. Simple Example: Let’s create a simple example where we have a Coffee class that can be decorated with various add-ons like milk and sugar. ...

The Composite Design Pattern is a structural pattern that allows you to compose objects into tree-like structures to represent part-whole hierarchies. This pattern treats both individual objects and compositions of objects uniformly. It’s useful when you need to work with hierarchies of objects and want to treat single objects and compositions of objects in a consistent way. Components of the Composite Design Pattern: Component: The abstract base class or interface that declares the common interface for both leaf and composite objects. Leaf: The concrete class that represents individual objects in the composition. It implements the component interface. Composite: The concrete class that represents compositions of leaf objects. It implements the component interface and contains child components. Simple Example: Let’s use a file system example where we have File and Directory components. A Directory can contain multiple File or Directory objects, and we want to be able to treat both File and Directory objects uniformly. ...

The Bridge Design Pattern is a structural pattern that separates an abstraction from its implementation, allowing the two to vary independently. This pattern is used to decouple an abstraction from its implementation so that the two can evolve separately without affecting each other. Components of the Bridge Design Pattern: Abstraction: Defines the abstract part of the interface that uses the implementation. RefinedAbstraction: Extends the Abstraction class and provides a specific implementation. Implementor: Defines the interface for implementation classes. ConcreteImplementor: Implements the Implementor interface and provides specific functionality. Example: Imagine you have a basic system where you need to handle different types of notifications, such as email and SMS. The goal is to separate the notification type (email or SMS) from the content of the notification. ...

The Adapter Design Pattern is a structural pattern that allows objects with incompatible interfaces to work together. It acts as a bridge, converting the interface of a class into another interface that clients expect. This pattern is useful when you want to use an existing class but its interface doesn’t match the one you need. Components of the Adapter Design Pattern: Target: The interface that the client expects to use. Adapter: Converts the interface of the Adaptee into the Target interface. Adaptee: The existing class with an incompatible interface that needs to be adapted. Client: Uses the Target interface to interact with the Adaptee via the Adapter. Simple Example: Let’s say we have a TemperatureSensor that provides temperature readings in Celsius, but our application needs temperature readings in Fahrenheit. We’ll create an adapter to convert Celsius readings to Fahrenheit. ...