Design patterns are a programming technique commonly used in software development to provide a common solution to improve the maintainability, scalability, and reusability of software when faced with a particular problem. Design patterns are a proven and widely used best practice. In this article, we will briefly introduce common design patterns.
I. Creation Patterns
1, Factory Method (Factory Method)
Factory Method Pattern is a design pattern for creating objects. It defines an interface to create objects and subclasses to implement this interface to create different objects. In this way, we can create objects without exposing the details of object creation. Factory method pattern helps us to solve the complexity while creating objects.
2, Abstract Factory (Abstract Factory)
The Abstract Factory pattern is an extension of the Factory Method pattern. It helps us to create a set of related objects rather than a single object. The Abstract Factory pattern defines an abstract factory interface, which a concrete factory implements to create objects. By using the abstract factory pattern, we can encapsulate the object creation process, thus making the client code simpler.
3, single instance pattern (Singleton)
Single instance pattern is a pattern that ensures that there is only one instance of a class. It does this by making the constructor of the class private. This prevents the creation of multiple instances through the constructor. The singleton pattern usually provides a static method to get the unique instance of the class. The singleton pattern helps us to ensure that there is only one instance globally and allows us to access this instance easily.
4, Builder pattern (Builder)
Builder pattern is a pattern used to create complex objects. It breaks down the process of constructing an object into multiple steps and allows different constructor methods to be used in each step. In this way, different objects can be created. The builder pattern can help us with the complexity of creating complex objects.
5, Prototype pattern (Prototype)
The prototype pattern is a pattern used to create objects. It allows us to create a new object by cloning an existing object. This way, we can create new objects without knowing the details of object creation. The prototype pattern helps us to increase the efficiency of object creation.
II. Structural Patterns
1. Adapter Pattern (Adapter)
Adapter Pattern is a pattern used to convert an incompatible interface to a compatible interface. The adapter pattern adapts different interfaces by wrapping an object. This allows otherwise incompatible interfaces to work with each other. The adapter pattern helps us to seamlessly integrate the old system with the new one.
2, bridge pattern (Bridge)
Bridge pattern is a pattern used to separate the abstract part from the implementation part. Bridge pattern by separating the abstract part from the realization of the part , so that they can be allowed to change independently. In this way, it is possible to modify the abstract part or the realization part without affecting the other parts.
3. Combination Pattern (Composite)
The combination pattern is a pattern used to combine objects into a tree structure. Composite pattern by combining objects into a tree structure, which allows client-side code to deal with individual objects and combinations of objects in a unified way. The combinatorial pattern helps us to simplify the structure of the code, which improves the readability and maintainability of the code.
4, Decorator pattern (Decorator)
Decorator pattern is a pattern used to add functionality at runtime. The decorator pattern allows functionality to be added dynamically at runtime by wrapping an object in another object. The decorator pattern helps us to break down complex functionality into simple functionality and allows us to easily extend the functionality of an object.
5, appearance pattern (Facade)
Appearance pattern is a pattern used to simplify the interface. The appearance pattern hides the complexity of the system by providing a simple interface. This makes the client code simpler. Appearance patterns help us to simplify the structure of the code and can improve the readability and maintainability of the code.
6, hedonic pattern (Flyweight)
Hedonic pattern is a pattern used to *** enjoy objects. The hedonic pattern allows multiple objects to *** enjoy the same state by separating the state of the *** enjoyment object. This reduces the number of objects and thus improves the performance of the system. The hedonic pattern helps us to optimize the performance of the system and can reduce the memory usage.
Three Behavioral Patterns
1. Chain of Responsibility (Chain of Responsibility)
The Chain of Responsibility pattern is a pattern used to process requests. The Chain of Responsibility pattern allows multiple objects to have a chance to process a request by passing it along a chain. The chain-of-duty pattern helps us break down complex business logic into simple logic and allows us to easily extend the objects that handle requests.
2, Command pattern (Command)
Command pattern is a pattern used to encapsulate operations. The command pattern allows us to handle different operations in a uniform way by encapsulating them into objects. The command pattern helps us to simplify the structure of our code and allows us to undo and redo operations easily.
3, Interpreter pattern (Interpreter)
Interpreter pattern is a pattern used to deal with the language. The interpreter pattern allows us to easily parse and execute the language by breaking it down into syntax trees. The interpreter pattern helps us to extend the syntax and functionality of the language and allows us to easily add new languages.
4, Iterator pattern (Iterator)
Iterator pattern is a pattern for accessing collections. Iterator pattern by encapsulating the process of traversing a collection into an object, which allows client code to access the elements of the collection in a uniform way. The iterator pattern helps us to simplify the structure of our code and allows us to easily extend the way collections are traversed.
5, Mediator pattern (Mediator)
Mediator pattern is a pattern used to handle the interaction between objects. The Mediator pattern can make interactions between objects easier by centralizing them in a mediator object. The mediator pattern helps us decouple interactions between objects and allows us to easily add new objects and interactions.
6, Memo mode (Memento)
Memo mode is a pattern used to save the state of an object. Memo mode by saving the state of the object in a memo object, which allows the object to restore the previous state in subsequent operations. The memo pattern helps us to implement undo and redo operations and allows us to easily save the historical state of an object.
7, Observer pattern (Observer)
Observer pattern is a pattern used to handle notifications between objects. The observer pattern can make notifications between objects easier by encapsulating them as events. The observer pattern helps us decouple notifications between objects and allows us to easily add new objects and notification methods.
8, State mode (State)
State mode is a pattern for dealing with the state of objects. The state pattern can make the state of an object clearer by breaking it down into different state classes. The state pattern helps us to simplify the structure of our code and allows us to easily extend the state of an object.
9, Strategy pattern (Strategy)
Strategy pattern is a pattern used to deal with algorithms. Strategy pattern by encapsulating the algorithm into different strategy classes, so that you can let the client code to choose a different algorithm. The strategy pattern helps us to simplify the structure of the code and allows us to easily extend the algorithm.
10, Template Method pattern (Template Method)
Template Method pattern is a pattern used to deal with algorithms. Template Method pattern by defining the skeleton of the algorithm in the abstract base class, which allows subclasses to implement specific algorithmic details. The template method pattern helps us to simplify the structure of our code and allows us to easily extend the skeleton and details of the algorithm.
11, Visitor pattern (Visitor)
Visitor pattern is a pattern used to deal with the structure of the object. The visitor pattern allows client code to access elements of an object structure in a uniform way by separating the object structure from the access operations. The visitor pattern helps us to simplify the code structure and allows us to easily add new access operations and element types.
12, hedonic pattern (Flyweight)
Like meta pattern is a pattern used to deal with a large number of similar objects. The hedonic pattern allows us to save memory and time overhead by *** enjoying the same state. The hedonic pattern can help us improve the performance of our program and allows us to easily add new object types.
Summary: Design patterns are a widely used software design methodology that can help us simplify code structure and improve program maintainability and scalability. In this article, we introduced 12 commonly used design patterns, including Factory Pattern, Singleton Pattern, Command Pattern, Interpreter Pattern, Iterator Pattern, Intermediary Pattern, Memo Pattern, Observer Pattern, State Pattern, Strategy Pattern, Template Method Pattern and Visitor Pattern.
Each design pattern has its own characteristics and uses, and we can choose the appropriate pattern to solve the problem according to different situations. Although design patterns can help us improve the quality and efficiency of our programs, overuse of design patterns can also bring some problems, such as increasing the complexity of the code and maintenance costs. Therefore, when using design patterns, we should weigh the pros and cons and make choices based on the actual situation.