golang map基础知识 golang

map初始化的四种方法

var myGreeting map[string]string fmt.Println(myGreeting)// map[] fmt.Println(myGreeting == nil) //truemyGreeting2 := make(map[string]string) myGreeting2["Tim"] = "Good morning." myGreeting2["Jenny"] = "Bonjour."fmt.Println(myGreeting2)//map[Jenny:Bonjour. Tim:Good morning.]myGreeting3 := map[string]string{} myGreeting3["Tim"] = "Good morning." myGreeting3["Jenny"] = "Bonjour." fmt.Println(myGreeting3)//map[Jenny:Bonjour. Tim:Good morning.]myGreeting4 := map[string]string{ "Time":"Good morning.", "Jenny": "Bonjour.", }fmt.Println(myGreeting4)//map[Jenny:Bonjour. Time:Good morning.] fmt.Println(myGreeting4["Jenny"]) //Bonjour.

map添加操作

myGreeting := map[string]string{ "Tim":"Good morning!", "Jenny": "Bonjour!", }myGreeting["Harleen"] = "Howdy"fmt.Println(myGreeting)

len 获取map的长度

myGreeting := map[string]string{ "Tim":"Good morning!", "Jenny": "Bonjour!", }myGreeting["Harleen"] = "Howdy"fmt.Println(len(myGreeting))

更新map

myGreeting := map[string]string{ "Tim":"Good morning!", "Jenny": "Bonjour!", }myGreeting["Harleen"] = "Howdy" fmt.Println(myGreeting) myGreeting["Harleen"] = "Gidday" fmt.Println(myGreeting)

删除map的值：

myGreeting := map[string]string{ "zero":"Good morning!", "one":"Bonjour!", "two":"Buenos dias!", "three": "Bongiorno!", }fmt.Println(myGreeting) delete(myGreeting, "two") fmt.Println(myGreeting) // ------------------------------------------------------------ myGreeting := map[int]string{ 0: "Good morning!", 1: "Bonjour!", 2: "Buenos dias!", 3: "Bongiorno!", }fmt.Println(myGreeting) delete(myGreeting, 7) fmt.Println(myGreeting)

判断key是否存在

myGreeting := map[int]string{ 0: "Good morning!", 1: "Bonjour!", 2: "Buenos dias!", 3: "Bongiorno!", }fmt.Println(myGreeting)// delete(myGreeting, 2)if val, exists := myGreeting[2]; exists { fmt.Println("That value exists.") fmt.Println("val: ", val) fmt.Println("exists: ", exists) } else { fmt.Println("That value doesn't exist.") fmt.Println("val: ", val) fmt.Println("exists: ", exists) }fmt.Println(myGreeting)

scoreMap := make(map[string]int) scoreMap["张三"] = 90 scoreMap["小明"] = 100 // 如果key存在ok为true,v为对应的值；不存在ok为false,v为值类型的零值 v, ok := scoreMap["张三"] if ok { fmt.Println(v) } else { fmt.Println("查无此人") }

map的遍历

myGreeting := map[int]string{ 0: "Good morning!", 1: "Bonjour!", 2: "Buenos dias!", 3: "Bongiorno!", }for key, val := range myGreeting { fmt.Println(key, " - ", val) } }