Adapter is:
creational pattern which defines an interface for creating objects, but delegates the actual responsibility for selecting the class and instantiating the object to a subclass
structural pattern that lets you add responsibilities to an object dynamically
structural pattern that adapts a class with an incompatible interface to fit your needs
Observer is:
behavioral pattern that allows an object to notify other objects when it changes (without knowing what the other objects are)
behavioral pattern that lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure. (Similar to Strategy but allows steps to be changed instead of whole implementation)
behavioral pattern that allows a class to use different variants of an algorithm
Factory method is:
creational pattern which provides an interface for creating families of related(or dependent) objects without specifying their concrete classes
Abstract Factory is:
Decorator is:
behavioral pattern which encapsulates a request as an object
Command is:
Use case for abstract factory:
system should be independent of product creation
want to configure with multiple families of products
want to ensure that a product family is used together
when an algorithm consists of varying and invariant parts that must be customized
a class can't anticipate the class of objects it must create
Use cases for factory method:
a class wants its subclasses to specify the objects it create
you need to use several subclasses, but its impractical to adapt their interfaces by subclassing each one
many classes differ only in their behavior
Use cases for decorator:
add responsibilities to individual objects dynamically and transparently
when responsibilities for objects can be withdrawn
when extension of functionality by subclassing is impractical
parameterize objects by an action to perform
client needs different variants of an algorithm
Use cases for command:
specify, queue, and execute requests at different times
structure a system around high-level operations built out of primitives
you want to create a reusable class that cooperates with unrelated classes that might not have compatible interfaces
Bridge pattern:
Decouples an abstraction from an implementation so the two can vary independently
Provides a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface making the subsystem easier to use.
Provide a surrogate or placeholder for another object to control access to it
Mediator is:
Defining an object that encapsulates how a set of objects interact.
A way for controlling communication between classes or entities.
Use sharing to support large numbers of fine-grained objects efficiently
Compose objects into tree structures to represent part-whole hierarchies
Chain of Responsibility is:
Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request
Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations
Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation
Define an object that encapsulates how a set of objects interact
Facade:
Provides a unified interface to a set of interfaces in a subsystem
Converts the interface of a class into another interface clients expect
Attaches additional responsibilities to an object dynamically
Provides a surrogate or placeholder for another object to control access to it
Flyweight:
Uses sharing to support large numbers of fine-grained objects efficiently
Specifies the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype
Defines the skeleton of an algorithm in an operation, deferring some steps to subclasses
Represents an operation to be performed on the elements of an object structure
Proxy:
Has a simulated object that mimics the behavior of a real object in controlled ways1
Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype
Define the skeleton of an algorithm in an operation, deferring some steps to subclasses
Visitor:
Lets you define a new operation without changing the classes of the elements on which it operates
Attach additional responsibilities to an object dynamically
Decouple an abstraction from an implementation so the two can vary independently
Define a family of algorithms, encapsulate each one, and make them interchangeable
Model-View-ViewModel:
Decouples the model from the view, uses data binding from the view to the middle layer, and allows UI/UX designers to work almost independently from application developers
Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically
Represent an operation to be performed on the elements of an object structure
Data Access Object:
Provides an abstract interface to some type of database or other persistence mechanism.
Defines a family of algorithms, encapsulate each one, and make them interchangeable
