golang语言map全方位介绍

package main
import (
	"fmt"
)  
func main(){
	//map的声明注意事项
	var a map[string]string
	// 在使用map前，首先要make 分配数据空间。
	a = make(map[string]string,10)
	a["no1"] = "松江"
	a["no2"] = "吴用"
	a["no3"] = "武松"
	a["no1"] = "吴用"
	fmt.Println(a)
}

var a map[string]string
	// 在使用map前，首先要make 分配数据空间。
	a = make(map[string]string,10)
	a["no3"] = "松江"
	a["no1"] = "吴用"
	a["no3"] = "武松"
	a["no2"] = "吴用"
	fmt.Println(a)

//第二种方式
	cities := make(map[string]string)
	cities["no1"] = "上海"
	cities["no2"] = "西安"
	cities["no3"] = "天津"
	fmt.Println(cities)

//第三种方式
	heroes := map[string]string{
		"no1" : "chengdu",    // 注意不能少了” ，“号
		"no2" : "beijing",
		"no3" : "wuhan",
	}
	fmt.Println(heroes)

cities := make(map[string]string)
	cities["no1"] = "上海"
	cities["no2"] = "西安"
	cities["no3"] = "天津"
	fmt.Println(cities)
	//因为no3 这个key值已经存在，所以下面的就是修改，若无就是增加
	cities["no3"] = "天津..."
	fmt.Println(cities)

//删除演示
	delete(cities,"no1")
	fmt.Println(cities)
	//当delete指定的key不存在时，删除不操作，也不会报错
	delete(cities,"no4")
	fmt.Println(cities)

//如果希望一次性删除所有  两种方式
	//1.遍历所有key，逐一删除
	//2.直接make一个新空间。
	cities := make(map[string]string)
	fmt.Println(cities)

//演示map查找
	val , ok :=cities["no2"]
	if ok{
		fmt.Printf("找到了  值为%v",val)
	}else{
		fmt.Printf("没有找到")
	}

package main
import (
	"fmt"
)  
func main(){
	cities := make(map[string]string)
	cities["no1"] = "上海"
	cities["no2"] = "西安"
	cities["no3"] = "天津"
	for k , v :=range cities{
		fmt.Printf("k=%v v=%v \n",k,v)
	}
}

package main
import (
	"fmt"
)  
func main(){
	cities := make(map[string]string)
	cities["no1"] = "上海"
	cities["no2"] = "西安"
	cities["no3"] = "天津"
	for k , v :=range cities{
		fmt.Printf("k=%v v=%v \n",k,v)
	}
	fmt.Println(len(cities))   //3
}

package main
import (
	"fmt"
)  
func main(){
	monsters := make([]map[string]string,2)
 
	if monsters[0] == nil{
		monsters[0] = make(map[string]string,2)
		monsters[0]["name"] = "牛魔王"
		monsters[0]["age"] = "500"
	}
	if monsters[1] == nil{
		monsters[1] = make(map[string]string,2)
		monsters[1]["name"] = "玉兔精"
		monsters[1]["age"] = "400"
	}
	//  这里如果我们继续使用monsters[2] 肯定越界  所以我们需要动态追加
	//这里我们需要使用切片的append函数，可以增加monsters
	//演示：
	newMonsters := map[string]string{
		"name" : "火云邪神",
		"age"  : "200",
	}
	//追加
	monsters = append(monsters,newMonsters)
	fmt.Println(monsters)
}

	map1 := make(map[int]int,100)
	map1[10] = 100
	map1[1] = 13
	map1[4] = 56
	map1[8] = 90
	for k , v :=range map1{
		fmt.Printf("k=%v  v=%v  \n",k , v)  //无序的
	}

//如果按照map的key的顺序进行排序输出
	//1. 先将map的key  放入到切片中
	//2.对切片排序
	//3. 遍历切片，然后按照key来输出map的值
	var keys[]int 
	for k , _ := range map1{
		keys = append(keys,k)
	}
	//排序
	sort.Ints(keys)
	fmt.Println(keys)  //输出key值
 
	for _ , k :=range keys{
		fmt.Printf("map1[%v]=%v \n",k,map1[k])
	}

package main
import (
	"fmt"
)  
func modify(map2 map[int]int ){
	map2[10] = 900
}
 
func main(){
	//map是引用类型，遵守引用类型传递机制，在一个函数接受map
	//修改后，会直接修改原来的map
	map1 := make(map[int]int)
	map1[1] = 90
	map1[2] = 88
	map1[10] = 1
	map1[20] = 2
 
	modify(map1)
	fmt. Println(map1) 
}