Go语言 map快速入门

map的两种定义方式

package main
import "fmt"
func main()  {
//map的定义

//key-value key一般为int/string
    //key不能重复，会覆盖, key是无序的，map是完全是无序的。
    //第一种方式 使用make
     map1 := make(map[string]string, 10)
     map1["a"]="hello"
     fmt.Println(map1)

     //第二种方式 声明直接赋值
     map2 := map[string]string{
        "a": "hello",
        "b": "world",
     }
     fmt.Println("map2:",map2)
 }

定义一个value是map类型的Map,来将学生数据信息存储。

     studentmap :=make(map[string]map[string]string,10)

     studentmap["1"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
     }
    studentmap["2"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
    }
    studentmap["3"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
    }

    studentmap["4"] = make(map[string]string,3)
    studentmap["4"]["name"]= "tom"
    studentmap["4"]["sex"]= "male"
    studentmap["4"]["address"]= "Tsingdao"

     fmt.Println(studentmap)

package main

import (
    "fmt"
)
func main()  {
//map的定义

//key-value key一般为int/string
    //key不能重复，会覆盖, key是无序的，map是完全是无序的。
    //第一种方式 使用make
     map1 := make(map[string]string, 10)
     map1["a"]="hello"
     fmt.Println(map1)

     //第二种方式 声明直接赋值
     map2 := map[string]string{
        "a": "hello",
        "b": "world",
     }
     fmt.Println("map2:",map2)

     studentmap :=make(map[string]map[string]string,10)
     studentmap["1"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
     }
    studentmap["2"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
    }
    studentmap["3"] = map[string]string{
        "name": "tom",
        "sex": "male",
        "address": "Beijing",
    }

    studentmap["4"] = make(map[string]string,3)
    studentmap["4"]["name"]= "tom"
    studentmap["4"]["sex"]= "male"
    studentmap["4"]["address"]= "Tsingdao"

    fmt.Println(studentmap)
    delete(studentmap,"1")
    fmt.Println("删除1后：", studentmap)

    //studentmap = make(map[string]map[string]string,10)
    //fmt.Println("删除后：", studentmap)

    val, ok := studentmap["1"]
    if ok{
        fmt.Println("有1",val)
    }
 //遍历map for -range
    for k, v := range studentmap{
        fmt.Println(k)
        for k2,v2 :=range v {
            fmt.Println(k2,v2)
        }
    }
    fmt.Println("studentmap有：", len(studentmap))

    //map 切片 slice of map map可以动态增加
    monsters := make([]map[string]string,2)
    monsters[0] =make(map[string]string,2)
    monsters[0]["name"] ="fat"
    monsters[0]["age"] = "3"
    monsters[1] =make(map[string]string,2)
    monsters[1]["name"] ="cat"
    monsters[1]["age"] = "4"
    //我们需要使用append函数，动态增加
    fmt.Println("monsters:",monsters)
     newmonster := map[string]string{
        "name":"love",
        "age" : "3",
     }
     monsters = append(monsters,newmonster)
     fmt.Println("增加后的monster:", monsters)

 }

对map的keys进行排序

首先创建一个空切片，使用for range将Map的keys全部导入到切片中，使用sort函数对keys切片进行排序，最后使用for range 对map进行输出操作。

     //map排序说明
     map3 := make(map[int]int,10)
     map3[10]=100
     map3[1]= 1
     map3[4] = 45

     //把Key放到切片中
      keys := make([]int,0) //定义一个空切片
     for k,_:= range map3{
        keys= append(keys,k)
     }
     sort.Ints(keys)

     for _,k :=range keys{
        fmt.Println(map3[k])
     }

使用结构体作为map的value，存储学生信息。

package main

import "fmt"

func main()  {
//map的定义

    //map的key为学号，map的值为结构体，包含名字，年龄和地址。
    type student struct {
        Name string
        Age int
        address string
    }

    students := make(map[string]student)
    stu1 := student{Name:"tom", Age : 18, address: "Beijing"}
    stu2 := student{Name:"Jack", Age : 22, address: "Weihai"}
    students["1"] = stu1
    students["2"] = stu2
    fmt.Println(students)
    for k,v :=range students{
        fmt.Println("编号:", k)
        fmt.Println("名字为", v.Name)
        fmt.Println("年龄为", v.Age)
        fmt.Println("地址为", v.address)
    }
 }