Design patterns of golang functions in object-oriented programming

Functions in Go play a vital role in object-oriented programming, they are the basis for building flexible and reusable code. By using functions, you can implement common design patterns, including: Singleton pattern: Ensures that only one instance of a class is created. Factory pattern: A factory method for creating objects. The client can specify the type of object to be created. Observer Pattern: Allows an object to register as an observer of another object and be notified when its state changes.

The design pattern of functions in object-oriented programming in Go

Function plays a vital role in object-oriented programming in Go role, they are the building blocks for building flexible and reusable code. This article will explore how to use Go functions in object-oriented programming and provide practical examples.

Design Patterns

Design patterns are reusable solutions to common programming problems. Here are some common design patterns implemented using Go functions:

• Singleton pattern: Ensures that only one instance of a class is created.
• Factory mode: Factory method to create objects, allowing the client to specify the type of object created.
• Observer pattern: An object can register as an observer for another object and be notified when the object's state changes.

Case: Singleton Pattern

The singleton pattern ensures that only a single instance of a class is created throughout the application. This is accomplished by creating a private constructor and a public method to obtain the instance.

package main

import "fmt"

type Singleton struct{}

var instance *Singleton

func GetInstance() *Singleton {
  if instance == nil {
    instance = &Singleton{}
  }

  return instance
}

func main() {
  s1 := GetInstance()
  s2 := GetInstance()

  if s1 == s2 {
    fmt.Println("Same instance")
  }
}

In this example, the GetInstance function is responsible for creating or getting a Singleton instance and ensuring that only one instance is created in the entire program.

Case: Factory Pattern

Factory pattern allows the client to specify the type of object to be created. This is accomplished by creating an interface and multiple different structures, each of which implements the interface.

package main

import "fmt"

type Item interface {
  GetName() string
}

type Book struct {
  name string
}

func (b *Book) GetName() string {
  return b.name
}

type Movie struct {
  name string
}

func (m *Movie) GetName() string {
  return m.name
}

type Factory struct {
  itemType string
}

func NewFactory(itemType string) *Factory {
  return &Factory{itemType: itemType}
}

func (f *Factory) CreateItem(name string) Item {
  switch f.itemType {
  case "book":
    return &Book{name}
  case "movie":
    return &Movie{name}
  }

  return nil
}

func main() {
  factory := NewFactory("book")
  item := factory.CreateItem("The Hitchhiker's Guide to the Galaxy")
  fmt.Println(item.GetName())
}

In this example, the Factory type allows the client to specify the type of project to create (book or movie). The CreateItem method is then responsible for creating items of a specific type.

Case: Observer Pattern

The Observer pattern allows an object to register as an observer of another object and be notified when the object's state changes. This is accomplished by creating an interface and multiple different structures, each of which implements the interface.

package main

import "fmt"

type Observable interface {
  AddObserver(observer Observer)
  RemoveObserver(observer Observer)
  NotifyObservers()
}

type Observer interface {
  Update()
}

type ConcreteObservable struct {
  observers []Observer
  state     int
}

func NewConcreteObservable() *ConcreteObservable {
  return &ConcreteObservable{
    observers: make([]Observer, 0),
  }
}

func (o *ConcreteObservable) AddObserver(observer Observer) {
  o.observers = append(o.observers, observer)
}

func (o *ConcreteObservable) RemoveObserver(observer Observer) {
  for i, obs := range o.observers {
    if obs == observer {
      o.observers = append(o.observers[:i], o.observers[i+1:]...)
      break
    }
  }
}

func (o *ConcreteObservable) NotifyObservers() {
  for _, observer := range o.observers {
    observer.Update()
  }
}

func (o *ConcreteObservable) SetState(state int) {
  o.state = state
  o.NotifyObservers()
}

type ConcreteObserver struct {
  name string
}

func NewConcreteObserver(name string) *ConcreteObserver {
  return &ConcreteObserver{name}
}

func (o *ConcreteObserver) Update() {
  fmt.Printf("Observer %s notified\n", o.name)
}

func main() {
  observable := NewConcreteObservable()

  observer1 := NewConcreteObserver("observer1")
  observer2 := NewConcreteObserver("observer2")

  observable.AddObserver(observer1)
  observable.AddObserver(observer2)

  observable.SetState(1)
  observable.SetState(2)
}

In this example, the ConcreteObservable type allows objects to register as observers and be notified when the Observable state changes. The ConcreteObserver type implements the Observer interface and provides an Update method to handle notifications.

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