GoLang 元素为 map 的 map

本篇文章介绍如何在 Go 语言中创建 Map 的 Map。

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GoLang Map 的 Map

Map的Map或嵌套映射是那些键值对值也是 Map 的 Map。 在 Go 语言中可以创建Map的Map。

当我们定义一个 Map 时，我们必须定义键和值的类型。 在这种情况下，key 的类型可以是 int、string 或任何其他类型，而 value 的类型将再次是 map。

语法：

var DemoMap = map[string]map[string]string{}
// 或者

var DemoMap = map[int]map[string]string{}

可以看到，DemoMap 定义了key字符串，int 类型，value 为 map 类型。 让我们举个例子。

代码：

package main
import "fmt"

func main() {
    DemoMap := map[int]map[string]string{
        1: {
            "one":   "Jiyik1",
            "two":   "Jiyik2",
            "three": "Jiyik3",
        },
        2: {
            "four": "Jiyik4",
            "five": "Jiyik5",
            "Six":  "Jiyik6",
        },
        3: {
            "seven": "Jiyik7",
            "eight": "Jiyik8",
            "nine":  "Jiyik9",
        },
        4: {
            "ten":    "Jiyik10",
            "eleven": "Jiyik11",
            "twelve": "Jiyik12",
        },
    }
    fmt.Println(DemoMap)
}

上面的代码创建了一个包含键整数和值 Map 的 Map ，然后打印该 Map。

输出：

map[
    1:map[one:Jiyik1 three:Jiyik3 two:Jiyik2]
    2:map[Six:Jiyik6 five:Jiyik5 four:Jiyik4]
    3:map[eight:Jiyik8 nine:Jiyik9 seven:Jiyik7]
    4:map[eleven:Jiyik11 ten:Jiyik10 twelve:Jiyik12]]

---

删除嵌套 Map

delete()parent map

让我们举个例子。

代码：

package main
import "fmt"

func main() {
    DemoMap := map[int]map[string]string{
        1: {
            "one":   "Jiyik1",
            "two":   "Jiyik2",
            "three": "Jiyik3",
        },
        2: {
            "four": "Jiyik4",
            "five": "Jiyik5",
            "Six":  "Jiyik6",
        },
        3: {
            "seven": "Jiyik7",
            "eight": "Jiyik8",
            "nine":  "Jiyik9",
        },
        4: {
            "ten":    "Jiyik10",
            "eleven": "Jiyik11",
            "twelve": "Jiyik12",
        },
    }
    delete(DemoMap, 3)
    fmt.Println(DemoMap)
}

上面的代码将从父 Map 中删除键 3 处的嵌套 Map。

输出：

map[
    1:map[one:Jiyik1 three:Jiyik3 two:Jiyik2]
    2:map[Six:Jiyik6 five:Jiyik5 four:Jiyik4]
    4:map[eleven:Jiyik11 ten:Jiyik10 twelve:Jiyik12]]

delete()

代码：

package main
import "fmt"

func main() {
    DemoMap := map[int]map[string]string{
        1: {
            "one":   "Jiyik1",
            "two":   "Jiyik2",
            "three": "Jiyik3",
        },
        2: {
            "four": "Jiyik4",
            "five": "Jiyik5",
            "Six":  "Jiyik6",
        },
        3: {
            "seven": "Jiyik7",
            "eight": "Jiyik8",
            "nine":  "Jiyik9",
        },
        4: {
            "ten":    "Jiyik10",
            "eleven": "Jiyik11",
            "twelve": "Jiyik12",
        },
    }
    delete(DemoMap[3], "seven")
    fmt.Println(DemoMap)
}

上面的代码将删除嵌套 Map 中键为 3 且成员键为 7 的成员。

输出：

map[
    1:map[one:Jiyik1 three:Jiyik3 two:Jiyik2]
    2:map[Six:Jiyik6 five:Jiyik5 four:Jiyik4]
    3:map[eight:Jiyik8 nine:Jiyik9]
    4:map[eleven:Jiyik11 ten:Jiyik10 twelve:Jiyik12]]

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迭代嵌套 Map

要遍历嵌套 Map ，我们必须使用 for 循环给出 Map 的索引号。 让我们举一个迭代嵌套 Map 的例子。

代码：

package main
import "fmt"

func main() {
    DemoMap := map[int]map[string]string{
        1: {
            "one":   "Jiyik1",
            "two":   "Jiyik2",
            "three": "Jiyik3",
        },
        2: {
            "four": "Jiyik4",
            "five": "Jiyik5",
            "Six":  "Jiyik6",
        },
        3: {
            "seven": "Jiyik7",
            "eight": "Jiyik8",
            "nine":  "Jiyik9",
        },
        4: {
            "ten":    "Jiyik10",
            "eleven": "Jiyik11",
            "twelve": "Jiyik12",
        },
    }
    for key, value := range DemoMap[3] {
        fmt.Println(key, value)
    }
}

上面的代码将迭代父 Map 中第三个位置的 Map。

输出：

seven Jiyik7
eight Jiyik8
nine Jiyik9