Golong 中的 Map

1. 声明式定义与创建

    //1. 声明式定义与创建

    nameMap := map[int]string{
        1: "hfliux",
        2: "future",
        3: "blog",
    }
    fmt.Println(nameMap)

2. make 函数进行创建

    //2. make函数进行创建

    scoreMap1 := make(map[string]int, 8)
    scoreMap1["张三"] = 90
    scoreMap1["小明"] = 100
    fmt.Println(scoreMap1)
    fmt.Println(scoreMap1["小明"])

3. 判断键值是否存在

    //3. 判断键值是否存在

    pwdMap := map[int]string{
        1: "lhf17777",
        2: "blog165",
        3: "admin123",
    }
    value, ok := pwdMap[18]
    if ok {
        fmt.Println(value)
    } else {
        fmt.Println("未有该用户")
    }

4. map 的遍历

    //4. map的遍历
    for key, value := range nameMap {
        fmt.Println(fmt.Sprintf("%d", key) + "---" + value)
    }

5. delete()函数删除 map 的元素

    /*
        5. delete()函数删除map的元素
    */
    cityMap := map[int]string{
        1: "北京",
        2: "上海",
        3: "广州",
        4: "深圳",
    }
    delete(cityMap, 2)
    fmt.Println(cityMap)

6. 小案例 1：按顺序遍历 map

    rand.Seed(time.Now().UnixNano()) //初始化随机数种子

    var scoreMap = make(map[string]int, 200)

    for i := 0; i < 100; i++ {
        key := fmt.Sprintf("stu%02d", i) //生成stu开头的字符串
        value := rand.Intn(100)          //生成0~99的随机整数
        scoreMap[key] = value
    }
    //取出map中的所有key存入切片keys
    var keys = make([]string, 0, 200)
    for key := range scoreMap {
        keys = append(keys, key)
    }
    //对切片进行排序
    sort.Strings(keys)
    //按照排序后的key遍历map
    for _, key := range keys {
        fmt.Println(key, scoreMap[key])
    }

7. 小案例 2：元素为 map 的切片

    var mapSlice = make([]map[string]string, 3)
    for index, value := range mapSlice {
        fmt.Printf("index:%d value:%v\n", index, value)
    }
    fmt.Println("after init")
    // 对切片中的map元素进行初始化
    mapSlice[0] = make(map[string]string, 10)
    mapSlice[0]["name"] = "小王子"
    mapSlice[0]["password"] = "123456"
    mapSlice[0]["address"] = "沙河"
    for index, value := range mapSlice {
        fmt.Printf("index:%d value:%v\n", index, value)
    }

8. 小案例 3：元素为切片的 map

    var sliceMap = make(map[string][]string, 3)
    fmt.Println(sliceMap)
    fmt.Println("after init")
    preKey := "中国"
    val, ok := sliceMap[preKey]
    if !ok {
        val = make([]string, 0, 2)
    }
    val = append(val, "北京", "上海")
    sliceMap[preKey] = val
    fmt.Println(sliceMap)