golang语言渐入佳境[17]-mapping表

//1、声明map的方式1
var map1 map[string]string


//2、声明map的方式2
map2 := make(map[string]string)

//3、map中key可以是：int、float、bool、string、数组
//	一定不可以是：切片、函数、map
var m1 map[int]string
var m2 map[float64]string
var m3 map[bool]string
var m4 map[string]string

var country = map[string]string{
	"China":  "Beijing",
	"Japan":  "Tokyo",
	"India":  "New Delhi",
	"France": "Paris",
	"Italy":  "Rome",
}
fmt.Println(country)

//短变量声明初始化方式
rating := map[string]float64{"c": 5, "Go": 4.5, "Python": 4.5, "C++": 3}
fmt.Println(rating)

countryMap := make(map[string]string)
countryMap["China"] = "Beijing"
countryMap["Japan"] = "Tokyo"
countryMap["India"] = "New Delhi"
countryMap["France"] = "Paris"
countryMap["Italy"] = "Rome"

for k, v := range countryMap {
  fmt.Println("国家", k, "首都", v)
}

for _, v := range countryMap {
  fmt.Println("国家",  "首都", v)
}

for k := range countryMap {
  fmt.Println("国家",  k , "首都", countryMap[k])
}

value , ok := countryMap["England"]
fmt.Printf("%q \n" , value)
fmt.Printf("%T , %v \n" , ok , ok)
if ok {
  fmt.Println("首都：" , value)
} else {
  fmt.Println("首都信息未检索到！")
}

//第二种方式
if value ,ok :=countryMap["USA"];ok {
  fmt.Println("首都：" , value)
} else {
  fmt.Println("首都信息未检索到！")
}

package main

import "fmt"

func main() {
//1、声明时同时初始化
var country = map[string]string{
"China":  "Beijing",
"Japan":  "Tokyo",
"India":  "New Delhi",
"France": "Paris",
"Italy":  "Rome",
	}
	fmt.Println(country)

//短变量声明初始化方式
	rating := map[string]float64{"c": 5, "Go": 4.5, "Python": 4.5, "C++": 3}
	fmt.Println(rating)

//2、创建map后再赋值
	countryMap := make(map[string]string)
	countryMap["China"] = "Beijing"
	countryMap["Japan"] = "Tokyo"
	countryMap["India"] = "New Delhi"
	countryMap["France"] = "Paris"
	countryMap["Italy"] = "Rome"

//	3、遍历map（无序）
//	(1)、key 、value都遍历
for k, v := range countryMap {
		fmt.Println("国家", k, "首都", v)
	}
	fmt.Println("-----------")

//(2)、只展示value
for _, v := range countryMap {
		fmt.Println("国家",  "首都", v)
	}
	fmt.Println("-----------")

//(3)、只展示key
for k := range countryMap {
		fmt.Println("国家",  k , "首都", countryMap[k])
	}
	fmt.Println("-----------")

//4、查看元素是否在map中存在
	value , ok := countryMap["England"]
	fmt.Printf("%q \n" , value)
	fmt.Printf("%T , %v \n" , ok , ok)
if ok {
		fmt.Println("首都：" , value)
	} else {
		fmt.Println("首都信息未检索到！")
	}

//或者
if value ,ok :=countryMap["USA"];ok {
		fmt.Println("首都：" , value)
	} else {
		fmt.Println("首都信息未检索到！")
	}
}

package main

import "fmt"

func main() {
//1、声明并初始化一个map
	map1 := map[string]string {
"element":"div",
"width" :"100px",
"height":"200px",
"border":"solid",
"background":"none",
	}

//2、根据key删除map中的某个元素
	fmt.Println("删除前：",map1)
if _,ok := map1["background"]; ok {
delete(map1 , "background")
	}
	fmt.Println("删除后：",map1)

//3、清空map
//map1 = map[string]string{}
	map1 = make(map[string]string)
	fmt.Println("清空后：",map1)
}