Design Pattern Flashcards
These are typical solutions to commonly occurring problems in software design. They are like pre-made blueprints that you can customize to solve a recurring design problem in your code.
Design Patterns
This pertains to what the object has
Object Composition
what the object is
object inheritance
DRY
Don’t Repeat Yourself
KISS
Keep It Simple Stupid
YAGNI
You ain’t gonna need it
Classes you create should have exactly one responsibility
Single Responsibility Principle (SRP)
OPEN for extension, CLOSED for modification
extend, override, overload
Open/Closed Principle
child classes or subclasses should be able to be used as substitute to parent class
if you replace an object of the parent class with an object of the subclass, the code should still work correctly
Liskov Substitution Principle
clients should not be forced to depend on methods they do not use
clients: methods / classes that use the interface
should be narrow enough, that the client don’t implement the ones it does not need
Interface Segregation Principle
High - level classes should not depend on low - level classes.
Both depend on abstractions.
Abstraction should not depend on details. Details depend on abstraction.
High - level classes: deals with overall functionality, directs low - level classes
Low - level classes: classes with specific details
Dependency Inversion Principle
Handles the creation of objects
These patterns provide various object creation mechanisms, which increase flexibility and reuse of existing code.
Creational Design Patterns
These patterns explain how to assemble objects and classes into larger structures while keeping these structures flexible and efficient.
uses interfaces to add functionality to objects
Structural Design Patterns
These patterns are concerned with algorithms and the assignment of responsibilities between objects.
Behavioral Design patterns
a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.
Factory Method
a creational design pattern that lets you produce families of related objects without specifying their concrete classes.
Abstract Factory
a creational design pattern that lets you construct complex objects step by step. The pattern allows you to produce different types and representations of an object using the same construction code.
Builder
a creational design pattern that lets you copy existing objects without making your code dependent on their classes.
Prototype
a creational design pattern that lets you ensure that a class has only one instance, while providing a global access point to this instance.
Singleton
is a structural design pattern that allows objects with incompatible interfaces to collaborate.
Adapter
a structural design pattern that lets you split a large class or a set of closely related classes into two separate hierarchies—abstraction and implementation—which can be developed independently of each other.
Bridge
a structural design pattern that lets you compose objects into tree structures and then work with these structures as if they were individual objects.
Composite
a structural design pattern that lets you attach new behaviors to objects by placing these objects inside special wrapper objects that contain the behaviors.
Decorator
a structural design pattern that provides a simplified interface to a library, a framework, or any other complex set of classes.
Facade
a structural design pattern that lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects instead of keeping all of the data in each object.
Flyweight
a structural design pattern that lets you provide a substitute or placeholder for another object. A proxy controls access to the original object, allowing you to perform something either before or after the request gets through to the original object.
Proxy
a behavioral design pattern that 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.
Chain of Responsibility
a behavioral design pattern that turns a request into a stand-alone object that contains all information about the request. This transformation lets you pass requests as a method arguments, delay or queue a request’s execution, and support undoable operations.
Command
a behavioral design pattern that lets you traverse elements of a collection without exposing its underlying representation (list, stack, tree, etc.).
Iterator
a behavioral design pattern that lets you reduce chaotic dependencies between objects. The pattern restricts direct communications between the objects and forces them to collaborate only via a mediator object.
Mediator
a behavioral design pattern that lets you save and restore the previous state of an object without revealing the details of its implementation.
Memento
a behavioral design pattern that lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.
Observer
a behavioral design pattern that lets an object alter its behavior when its internal state changes. It appears as if the object changed its class.
State
a behavioral design pattern that lets you define a family of algorithms, put each of them into a separate class, and make their objects interchangeable.
Strategy
a behavioral design pattern that defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure.
Template Method
a behavioral design pattern that lets you separate algorithms from the objects on which they operate.
Visitor
why prefer composition over inheritance
composition offers several advantages over inheritance, including greater flexibility, reduced complexity, and improved maintainability. It can also avoid problems associated with multiple inheritance, such as the “diamond problem.” While inheritance still has its place in object-oriented programming.
