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)
}
}
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