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一、 Go是面向对象的吗?

Go is not a pure object oriented programming language. This excerpt taken from Go's FAQs answers the question of whether Go is Object Oriented.

Yes and no. Although Go has types and methods and allows an object-oriented style of programming, there is no type hierarchy. The concept of “interface” in Go provides a different approach that we believe is easy to use and in some ways more general. There are also ways to embed types in other types to provide something analogous—but not identical—to subclassing. Moreover, methods in Go are more general than in C++ or Java: they can be defined for any sort of data, even built-in types such as plain, “unboxed” integers. They are not restricted to structs (classes)
In the upcoming tutorials, we will discuss how object oriented programming concepts can be implemented using Go. Some of them are quite different in implementation compared to other object oriented languages such as Java.

Go不是一种纯粹的面向对象编程语言。这段摘自Go的faq，回答了Go是否是面向对象的问题。
是也不是。虽然Go有类型和方法，并且允许面向对象的编程风格，但是没有类型层次结构。Go中的“接口”概念提供了一种不同的方法，我们认为这种方法易于使用，并且在某些方面更通用。还有一些方法可以将类型嵌入到其他类型中，以提供类似于子类化(但不完全相同)的东西。此外，Go中的方法比c++或Java中的方法更通用:可以为任何类型的数据定义方法，甚至可以为内置类型(如普通的“未装箱”整数)定义方法。它们并不局限于结构体(类)。
在接下来的教程中，我们将讨论如何使用Go实现面向对象编程概念。它们中的一些在实现上与其他面向对象语言(如Java)有很大的不同。

二、Structs Instead of Classes 结构体 - OOP in Go

        // 目录结构│   └── oop│       ├── employee│       │   └── employee.go│       ├── go.mod│       └── main.go// main.gopackage mainimport ("oop/employee")func main() {e := employee.Employee{FirstName: "Mei", LastName: "Jin", TotalLeaves: 666, LeavesTaken: 555}e.LeavesRemaining()var c employee.Employeec.LeavesRemaining()d := employee.New("Liang", "xiaoxiao", 888, 777)d.LeavesRemaining()}// employee.gopackage employeeimport "fmt"type Employee struct {FirstName   stringLastName    stringTotalLeaves intLeavesTaken int}func New(firstName string, lastName string, totalLeave int, leavesTaken int) Employee {e := Employee{firstName, lastName, totalLeave, leavesTaken}return e}func (e Employee) LeavesRemaining() {fmt.Printf("%s %s has %d leaves remaining\n", e.FirstName, e.LastName, (e.TotalLeaves - e.LeavesTaken))}// 运行结果// Mei Jin has 111 leaves remaining// has 0 leaves remaining// Liang xiaoxiao has 111 leaves remaining

三、 Composition Instead of Inheritance 组合嵌套 - OOP in Go

1.Composition by embedding structs

        package mainimport (  "fmt")type author struct {  firstName stringlastName  stringbio       string}func (a author) fullName() string {  return fmt.Sprintf("%s %s", a.firstName, a.lastName)}type blogPost struct {  title   stringcontent stringauthor}func (b blogPost) details() {  fmt.Println("Title: ", b.title)fmt.Println("Content: ", b.content)fmt.Println("Author: ", b.fullName())fmt.Println("Bio: ", b.bio)}func main() {  author1 := author{"MeiJin","Liang","Golang Enthusiast",}blogPost1 := blogPost{"Inheritance in Go","Go supports composition instead of inheritance",author1,}blogPost1.details()}// Title: Inheritance in GO// Content: GO supports composition instead of inheritance// Author: MeiJin Liang// Bio: Golang Enthusiast

2. Embedding slice of structs

        package mainimport "fmt"type Author struct {firstName stringlastName  stringbio       string}func (a Author) fullName() string {return fmt.Sprintf("%s %s", a.firstName, a.lastName)}type BlogPost struct {title   stringcontent stringAuthor}func (p BlogPost) details() {fmt.Println("Title:", p.title)fmt.Println("Content:", p.content)fmt.Println("Author:", p.fullName()) // 注意调用的是blogpost里author的fillName方法fmt.Println("Bio:", p.bio)}type WebSite struct {BlogPosts []BlogPost}func (w WebSite) contents() {fmt.Println("Contents of Website\n")for _, v := range w.BlogPosts {v.details()fmt.Println()}}func main() {author := Author{"MeiJin","Liang","Golang Enthusiast",}blogpost1 := BlogPost{"Inheritance in GO","GO supports composition instead of inheritance",author,}blogPost2 := BlogPost{"Struct instead of Classes in Go","Go does not support classes but methods can be added to structs",author,}blogPost3 := BlogPost{"Concurrency","Go is a concurrent language and not a parallel one",author,}w := WebSite{BlogPosts: []BlogPost{blogpost1, blogPost2, blogPost3},}w.contents()}// Contents of Website// Title: Inheritance in GO// Content: GO supports composition instead of inheritance// Author: MeiJin Liang// Bio: Golang Enthusiast// Title: Struct instead of Classes in Go// Content: Go does not support classes but methods can be added to structs// Author: MeiJin Liang// Bio: Golang Enthusiast// Title: Concurrency// Content: Go is a concurrent language and not a parallel one// Author: MeiJin Liang// Bio: Golang Enthusiast

四、Polymorphism 多态 - OOP in Go

1. Polymorphism using an interface

        package mainimport "fmt"type Income interface {calculate() intsource() string}type FixedBilling struct {projectName  stringbiddedAmount int}type TimeAndMaterial struct {projectName stringnoOfHours   inthourlyRate  int}func (fb FixedBilling) calculate() int {return fb.biddedAmount}func (fb FixedBilling) source() string {return fb.projectName}func (tm TimeAndMaterial) calculate() int {return tm.noOfHours * tm.hourlyRate}func (tm TimeAndMaterial) source() string {return tm.projectName}func calculateNetIncome(ic []Income) {		// 设置一个变量 每次循环更新一次 最后为结果var netincome int = 0for _, income := range ic {fmt.Printf("Income From %s = $%d\n", income.source(), income.calculate())netincome += income.calculate()}fmt.Printf("Net income of organization = $%d", netincome)}func main() {project1 := FixedBilling{projectName: "Project 1", biddedAmount: 5000}project2 := FixedBilling{projectName: "Project 2", biddedAmount: 10000}project3 := TimeAndMaterial{projectName: "Project 3", noOfHours: 160, hourlyRate: 25}incomeStreams := []Income{project1, project2, project3}calculateNetIncome(incomeStreams)}// Income From Project 1 = $5000// Income From Project 2 = $10000// Income From Project 3 = $4000// Net income of organization = $19000

2. Adding a new income stream to the above program

        package mainimport "fmt"type Income interface {calculate() intsource() string}type FixedBilling struct {projectName  stringbiddedAmount int}type TimeAndMaterial struct {projectName stringnoOfHours   inthourlyRate  int}type Advertisement struct {adName     stringCPC        intnoOfClicks int}func (fb FixedBilling) calculate() int {return fb.biddedAmount}func (fb FixedBilling) source() string {return fb.projectName}func (tm TimeAndMaterial) calculate() int {return tm.noOfHours * tm.hourlyRate}func (tm TimeAndMaterial) source() string {return tm.projectName}func (a Advertisement) calculate() int {return a.CPC * a.noOfClicks}func (a Advertisement) source() string {return a.adName}func calculateNetIncome(ic []Income) {var netincome int = 0for _, income := range ic {fmt.Printf("Income From %s = $%d\n", income.source(), income.calculate())netincome += income.calculate()}fmt.Printf("Net income of organization = $%d", netincome)}func main() {project1 := FixedBilling{projectName: "Project 1", biddedAmount: 5000}project2 := FixedBilling{projectName: "Project 2", biddedAmount: 10000}project3 := TimeAndMaterial{projectName: "Project 3", noOfHours: 160, hourlyRate: 25}bannerAd := Advertisement{adName: "Banner Ad", CPC: 2, noOfClicks: 500}popupAd := Advertisement{adName: "Popup Ad", CPC: 5, noOfClicks: 750}incomeStreams := []Income{project1, project2, project3, bannerAd, popupAd}calculateNetIncome(incomeStreams)}// Income From Project 1 = $5000// Income From Project 2 = $10000// Income From Project 3 = $4000// Income From Banner Ad = $1000// Income From Popup Ad = $3750// Net income of organization = $23750

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