map/字典

key-value的数据结构，又叫字典或关联数组（map是无序的）

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声明：

var map1 map[keytype]valuetype var a map[string]string var a map[string]int var a map[int]string var a map[string]map[string]string

声明是不会分配内存的，初始化需要make

创建方式：

package main import "fmt" func main() { a := make(map[string]string, 10) fmt.Println(a) a["a"] = "aa" a["b"] = "bb" fmt.Println(a) var b map[string]string = map[string]string { "b1": "v1", "b2": "v2", } fmt.Println(b) var c = map[string]string { "c1": "v1", "c2": "v2", } fmt.Println(c) d := map[string]string { "d1": "v1", "d2": "v2", } fmt.Println(d) }

输出：
map[]
map[a:aa b:bb]
map[b1:v1 b2:v2]
map[c1:v1 c2:v2]
map[d1:v1 d2:v2]

Process finished with exit code 0

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map相关操作：

var a map[string]string = map[string]string{“hello”: “world”} a = make(map[string]string, 10) a[“hello”] = “world”//插入和更新 Val, ok := a[“hello”]//查找 for k, v := range a {//遍历 fmt.Println(k,v) } delete(a, “hello”)//删除 len(a)//长度

查找/修改的用法举例：

func modify(a map[string]map[string]string) { _, ok := a["zhangsan"] if !ok { //要记得初始化(是map类型的)值 a["zhangsan"] = make(map[string]string) } a["zhangsan"]["passwd"] = "123456" a["zhangsan"]["nickname"] = "pangpang" return } func testMap3() { a := make(map[string]map[string]string, 100) modify(a) fmt.Println(a) } func main() { testMap3() } 

遍历值为map的map：

package main import "fmt" func trans(a map[string]map[string]string) { for k, v := range a { fmt.Println(k) for k1, v1 := range v { fmt.Println("\t", k1, v1) } } } func main() { a := make(map[string]map[string]string, 100) a["key1"] = make(map[string]string) a["key1"]["key2"] = "abc" a["key1"]["key3"] = "abc" a["key1"]["key4"] = "abc" a["key1"]["key5"] = "abc" a["key2"] = make(map[string]string) a["key2"]["key2"] = "abc" a["key2"]["key3"] = "abc" trans(a) delete(a, "key1") fmt.Println() trans(a) fmt.Println(len(a)) }

输出：
key1
key2 abc
key3 abc
key4 abc
key5 abc
key2
key2 abc
key3 abc

key2
key2 abc
key3 abc
1

Process finished with exit code 0
map是引用类型

func modify(a map[string]int) { a[“one”] = 134 }

slice of map：

Items := make([]map[int][int], 5) For I := 0; I < 5; i++ { items[i] = make(map[int][int]) }

map排序：

a. 先获取所有key，把key进行排序 b. 按照排序好的key，进行遍历

map反转：

a. 初始化另外一个map，把key、value互换即可

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map的值也可以是map：

a := make(map[string]map[string]string, 10) /*//报错！作为值的map[string]string也要初始化才行 a["k1"]["k2"] = "哈哈" fmt.Println(a)*/ //作为值的map[string]string也要初始化才行！ a["k1"] = make(map[string]string) a["k1"]["k2"] = "哈哈" a["k1"]["k3"] = "呵呵" a["k1"]["k4"] = "嘿嘿" fmt.Println(a)