结构体&练习

结构体

定义

Go中的面向对象是通过 struct来实现的,struct是用户自定义的类型

//定义结构体
/定义结构体
type User struct {
 Name string
 Gender string
 Age int
 AvatarUrl string
}
func useStruct() {
 //初始化结构体1
 var user1 User
 user1.Name = "jeson"
 user1.Gender = "male"
 user1.Age = 20
 user1.AvatarUrl = "http://baidu.com"
 //初始化结构体2
 user2 := User{
 Name: "miky",
 Gender: "female",
 Age: 18,
 }
 fmt.Println(user1,user2)
 //空结构体
 user3 := User{}
 fmt.Println(user3)
}

结构体的特性

• struct的内存布局:占用一段连续的内存空间
• 结构体没有构造函数,需要自己实现

//定义结构体
type User struct {
 Name string
 Gender string
 Age int
 AvatarUrl string
}
// 定义构造函数
func NewUser(name,gender string,age int,url string) User {
 var user User
 user.Name = name
 user.Gender = gender
 user.Age = age
 user.AvatarUrl = url
 return user
}
//使用构造函数
func main() {
 user1 := NewUser("zhansan","male",23,"xxx")
 fmt.Println(user1)
}

匿名字段和嵌套的使用

type People struct {
 Name string
 Gender string
 Age int
 AvatarUrl string
 //匿名字段
 int
 string
 //结构体嵌套
 address Address
}
type Address struct {
 City string
 Province string
}
func nimingStructs() {
 var people People
 people.Name = "abc"
 people.Gender = "male"
 people.AvatarUrl = "www.qq.com"
 //直接用结构体名引用匿名字段
 people.int = 99
 people.string = "hello world"
 //嵌套结构体的使用
 people.address.City = "beijing"
 people.address.Province = "beijing"
 fmt.Printf("%#v\n",people)
 //
 people1 := People{
 Name: "alley",
 Gender: "male",
 Age: 12,
 AvatarUrl: "www.baidu.com",
 int: 0,
 string: "dd",
 address: Address{
 City: "Lanzhou",
 Province: "Gansu",
 },
 }
 fmt.Printf("%#v\n",people1)
}

• 匿名结构体: 继承
• 字段可见性: 大写表示公开可以访问,小写表示私有

tag与结构体的应用

tag是结构体原信息,可以在运行的时候通过反射的机制读取出来

type User struct {
 Name string `json:"name"`
 Gender string `json:"gender"`
 Age int `json:"age"`
 AvatarUrl string `json:"avataurl"`
}
func jsonMarshal () {
 var user User
 user.Name = "jeck"
 user.Gender = "male"
 user.Age = 20
 user.AvatarUrl = "xxx"
 //json 格式
 data,err := json.Marshal(user)
 if err != nil {
 fmt.Printf("marshal failed %v\n",err)
 return
 }
 fmt.Printf("json:%v\n",string(data))
}

练习

• 实现1-100内的质数的打印

func isPrime(n int) bool {
 var flag = true
 for j:=2;j<n;j++ {
 if (n%j==0) {
 flag = false
 break
 }
 }
 return flag
}
func zhishu() {
 var n int
 fmt.Printf("Please input n:\n")
 fmt.Scanf("%d",&n)
 for i := 2;i<n;i++ {
 if isPrime(i) {
 fmt.Printf("%d is prime\n",i)
 }
 }
}

• 输入一行字符,分别计算簇字母空格数字和其他字符的个数

v1初始版

func main() {
 str := "how are you! i am fine! thank you.welcome"
 var tmp []rune
 var wordCount map[string]int = make(map[string]int,10)
 var chars []rune = []rune(str)
 for i:=0; i<len(str);i++ {
 if (str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z') {
 tmp = append(tmp,chars[i])
 }else {
 word := string(tmp)
 if len(word) > 0 {
 count,ok := wordCount[word]
 if !ok {
 wordCount[word] = 1
 } else {
 wordCount[word] = count+1
 }
 }
 tmp = tmp[0:0]
 }
 }
 if len(tmp) > 0{
 word := string(tmp)
 if len(word) > 0 {
 count,ok := wordCount[word]
 if !ok {
 wordCount[word] = 1
 } else {
 wordCount[word] = count+1
 }
 }
 }
 for key,val := range wordCount {
 fmt.Printf("word:%s,出现的次数%d\n",key,val)
 }
}

v2函数抽象版本

func addWorld(wordCount map[string]int,chars []rune) {
 word := string(chars)
 if len(word) > 0 {
 count,ok := wordCount[word]
 if !ok {
 wordCount[word] = 1
 } else {
 wordCount[word] = count+1
 }
 }
}
func main() {
 str := "how are you! i am fine! thank you.welcome"
 var tmp []rune
 var wordCount map[string]int = make(map[string]int,10)
 var chars []rune = []rune(str)
 for i:=0; i<len(str);i++ {
 if (str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z') {
 tmp = append(tmp,chars[i])
 }else {
 addWorld(wordCount,tmp)
 tmp = tmp[0:0]
 }
 }
 if len(tmp) > 0{
 addWorld(wordCount,tmp)
 }
 for key,val := range wordCount {
 fmt.Printf("word:%s,出现的次数%d\n",key,val)
 }
}

• 字符统计(包含中文)

func addWord(charCount map[rune]int,char rune){
 count,ok := charCount[char]
 if !ok {
 charCount[char] = 1
 }else {
 charCount[char] = count +1
 }
}
func main() {
 str := "sds sds,Let us go go go,学习好的 any sds!@lili"
 var charCount map[rune]int = make(map[rune]int,10)
 var chars []rune = []rune(str)
 for i:=0;i<len(chars);i++ {
 addWord(charCount,chars[i])
 }
 for key,val := range charCount {
 fmt.Printf("keys:%c val: %d\n",key,val)
 }
}

• 实现一个学生管理系统,每个学生有分数,年级,性别,名字等信息,用户可以在控制台添加学生,修改学生信息,打印学生列表的功能

type Student struct {
 Id string `json:"id"`
 Name string `json:"name"`
 Age int `json:"name"`
 Gender string `json:"gender"`
 Score float32 `json:"score"`
}
func showMenu() {
 fmt.Printf("please select:\n")
 fmt.Printf("1. 添加学生信息\n")
 fmt.Printf("2. 修改学生信息\n")
 fmt.Printf("3. 显示学生信息\n")
 fmt.Printf("4. 退出\n")
}
func getStudentInfo() Student {
 var stu Student
 fmt.Printf("please input id:\n")
 fmt.Scanf("%s\n",&stu.Id)
 fmt.Printf("please input name:\n")
 fmt.Scanf("%s\n",&stu.Name)
 fmt.Printf("please input age:\n")
 fmt.Scanf("%d\n",&stu.Age)
 fmt.Printf("please input gender:\n")
 fmt.Scanf("%s\n",&stu.Gender)
 fmt.Printf("please input score:\n")
 fmt.Scanf("%f\n",&stu.Score)
 return stu
}
func addStudent(allStudent map[string]Student) {
 stu := getStudentInfo()
 _,ok := allStudent[stu.Id]
 if ok {
 fmt.Printf("student %s is exists\n",stu.Id)
 return
 }
 allStudent[stu.Id] = stu
}
func showStudentList(allStudent map[string]Student) {
 for _,val := range allStudent {
 fmt.Printf("#########分隔线##########\n")
 fmt.Printf("id:%s\n",val.Id)
 fmt.Printf("name:%s\n",val.Name)
 fmt.Printf("age:%d\n",val.Age)
 fmt.Printf("gender:%s\n",val.Gender)
 fmt.Printf("score:%f\n",val.Score)
 fmt.Printf("#########分隔线##########\n")
 }
}
func modifyStudent(allStudent map[string]Student) {
 stu := getStudentInfo()
 _,ok := allStudent[stu.Id]
 if !ok {
 fmt.Printf("student %s is not exists\n",stu.Id)
 return
 }
 allStudent[stu.Id] = stu
}
func main() {
 var allStudent map[string]Student = make(map[string]Student,100)
 for {
 showMenu()
 var sel int
 fmt.Scanf("%d\n",&sel)
 switch sel {
 case 1:
 addStudent(allStudent)
 case 2:
 modifyStudent(allStudent)
 case 3:
 showStudentList(allStudent)
 case 4:
 os.Exit(0)
 }
 }
}

本文来自:51CTO博客

感谢作者:wx5b285b48ed74e

查看原文:Go语言入门(五)结构体&练习

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