关于golang:golang-map基础知识

map初始化的四种办法

    var myGreeting map[string]string    fmt.Println(myGreeting)        // map[]    fmt.Println(myGreeting == nil) //true    myGreeting2 := 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增加操作

    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)    }}

   scoreMap := make(map[string]int)    scoreMap["张三"] = 90    scoreMap["小明"] = 100    scoreMap["王五"] = 60    for k := range scoreMap {        fmt.Println(k)    }