Dive Into Design Patterns Pdf Github Top -

Unpopular opinion: Design Patterns aren't just for interviews. They are the secret weapon against spaghetti code. 🍝🚫

: High-level modules should not depend on low-level modules; both should depend on abstractions. Design Pattern Categories dive into design patterns pdf github top

These patterns take care of effective communication and the assignment of responsibilities between objects. Design Pattern Categories These patterns take care of

| Pattern | Core Idea | A Common Use Case | | :--- | :--- | :--- | | | Lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain. | An expense approval system where requests go through a chain of managers, each with different spending limits. | | Command | Turns a request into a stand-alone object that contains all information about the request. This transformation lets you parameterize methods, queue or log requests, and support undoable operations. | Implementing undo/redo functionality in a text editor, where each action (paste, delete) is a separate command object. | | Iterator | Lets you traverse elements of a collection without exposing its underlying representation (list, stack, tree, etc.). | Creating a standard way to loop through items in a custom data structure like a graph. | | Mediator | Reduces chaotic dependencies between objects by providing a central mediator object that handles all the communication between them. | The control tower at an airport acts as a mediator, coordinating takeoffs and landings between planes. In software, a chat room could be a mediator for users. | | Memento | Lets you save and restore the previous state of an object without revealing the details of its implementation. | Implementing save points in a video game, where the game's state (position, health, inventory) is captured as a memento object. | | Observer | Defines a subscription mechanism to allow multiple objects to listen and react to events happening in another object they are observing. | In a spreadsheet, a chart is an observer of the data table; when the data changes, the chart updates automatically. | | State | Allows an object to alter its behavior when its internal state changes. The object will appear to change its class. | As mentioned earlier, a light switch behaves differently when it's "on" vs. "off". A vending machine's behavior changes based on whether or not it has received enough money. | | Strategy | Defines a family of algorithms, puts each of them in a separate class, and makes their objects interchangeable. | A navigation app can use different strategies: RoadStrategy , WalkingStrategy , PublicTransportStrategy . The app's behavior changes based on the user's choice. | | Template Method | Defines the skeleton of an algorithm in a superclass but lets subclasses override specific steps of the algorithm without changing its structure. | The classic buildHouse() algorithm has steps like buildFoundation() , buildWalls() , buildRoof() . These steps can be overridden for a wooden house or a brick house. | | Visitor | Lets you separate algorithms from the objects on which they operate. You can add new behaviors to existing classes without modifying them. | Adding a system for exporting data from a complex object structure (like an AST in a compiler) into different formats (XML, JSON) without changing the original classes. | | An expense approval system where requests go