What are the commonly used design patterns in the golang framework?

Common design patterns in the Go framework include: singleton pattern: a class that ensures only one instance; factory pattern: creates an object without specifying its specific type; visitor pattern: adds new operations to an existing object structure. These patterns help improve the scalability, flexibility, and maintainability of Go applications.

Commonly used design patterns in the Go framework

Design patterns are a set of reusable solutions to common software development problems . They provide a standardized way to solve specific types of code structure or behavioral problems.

The Go framework provides a series of built-in design patterns that simplify and modularize your code base. Here are some of the most commonly used design patterns:

Singleton Pattern

The Singleton pattern ensures that there is only one instance of a class. Typically used to manage shared access to resources, such as database connections or configuration objects.

type MySingleton struct {
    instance *singleton
}

func (s *MySingleton) GetInstance() *singleton {
    if s.instance == nil {
        s.instance = newSingleton()
    }
    return s.instance
}

func newSingleton() *singleton {
    return &singleton{}
}

Factory Pattern

The factory pattern is responsible for creating objects but does not specify their exact type. Allows changing the type of objects created in the application without modifying the client code.

type Factory interface {
    Create() Product
}

type ConcreteFactory1 struct {}

func (f *ConcreteFactory1) Create() Product {
    return &ConcreteProduct1{}
}

type ConcreteFactory2 struct {}

func (f *ConcreteFactory2) Create() Product {
    return &ConcreteProduct2{}
}

type Product interface { ... }

type ConcreteProduct1 struct {}
type ConcreteProduct2 struct {}

Visitor Pattern

The Visitor pattern allows you to add new operations to existing object structures without modifying them themselves. This allows various operations to be performed without changing the object.

type Visitor interface {
    Visit(subj Subject) string
}

type Subject interface {
    Accept(v Visitor) string
}

type ConcreteSubject1 struct {}

func (s *ConcreteSubject1) Accept(v Visitor) string {
    return v.Visit(s)
}

type ConcreteVisitor1 struct {}

func (v *ConcreteVisitor1) Visit(subj Subject) string {
    return "ConcreteVisitor1 visited ConcreteSubject1"
}

Practical case:

Single case mode:

// 数据库连接单例
var db *sql.DB

func GetDB() *sql.DB {
    if db == nil {
        db, _ = sql.Open("mysql", "user:password@tcp(host:port)/database")
    }
    return db
}

Factory mode:

// 创建不同类型对象的工厂
func CreateRenderer(rendererType string) Renderer {
    switch rendererType {
    case "text":
        return &TextRenderer{}
    case "html":
        return &HTMLRenderer{}
    default:
        panic("Unknown renderer type")
    }
}

Visitor Pattern:

// 用于对不同类型对象执行不同操作的访问者
func VisitShapes(shapes []Shape, v Visitor) {
    for _, shape := range shapes {
        fmt.Println(shape.Accept(v))
    }
}

// 不同类型的形状对象
type Circle struct {}
type Square struct {}

// 形状的接受方法，接受访问者并执行特定操作
func (c *Circle) Accept(v Visitor) string {
    return v.VisitCircle(c)
}

func (s *Square) Accept(v Visitor) string {
    return v.VisitSquare(s)
}

// 访问者接口，定义对不同形状对象的访问操作
type Visitor interface {
    VisitCircle(c *Circle) string
    VisitSquare(s *Square) string
}

By using these design patterns, you can improve the scalability, flexibility, and maintainability of your Go applications.

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