go-map

package main

import "fmt"

/**
声明
var m map[int]string
var b
a :=

赋值
map[int]string{}
map[int]string{1: "a", 2: "b", 4: "c"}
make(map[int]string)


*/
func main() {

    var m map[int]string
    m = map[int]string{}
    fmt.Println(m)

    var n map[int]string
    n = make(map[int]string)
    fmt.Println(n)

    var b = make(map[int]string)
    fmt.Println(b)

    a := make(map[int]string)
    fmt.Println(a)
    a[1] = "ok"
    fmt.Println(a) //输出map
    aa := a[1]
    fmt.Println(aa) //输出map的键对应的值

    //复杂map-键对应也是map--使用map需要初始化
    var x map[int]map[int]string
    x = make(map[int]map[int]string)
    x[1] = make(map[int]string)
    //键为1的map的键为1的值
    x[1][1] = "ok"
    xx := x[1][1]
    yy := x[1][2]
    fmt.Println(xx)
    fmt.Println(yy) //空字符串

    //p返回value,ok返回bool类型-键值对是否存在
    p, ok := x[1][2]
    if !ok {
        x[1][2] = "aaa"
        p, ok = x[1][2]
    }
    fmt.Println(p, ok)
    fmt.Println("--------------迭代-----------------")

    //以map为类型的slice,长度为5
    sm := make([]map[int]string, 5, 10)
    //迭代操作---索引、值
    //得到的v是拷贝，不会对sm造成影响
    for _, v := range sm {
        v = make(map[int]string, 2)
        v[1] = "ok1"
        v[2] = "ok2"
        fmt.Println(v)
    }
    fmt.Println(sm)

    fmt.Println("---------遍历切片类型的map集合,相当于foreach---------")
    smm := make([]map[int]string, 5)
    for iii := range smm {
        //smm[iii] = make(map[int]string) 这样也可以
        smm[iii] = make(map[int]string, 1)
        smm[iii][1] = "aaaaaa"
        smm[iii][2] = "aaaddaaa"
        fmt.Println(smm[iii])
    }
    fmt.Println(smm)

    fmt.Println("---------遍历map的键---------")
    r := map[int]string{1: "a", 2: "b", 4: "c"} //初始化一个map
    sortKey := make([]int, len(r))              //初始化一个存map键的切片
    //遍历操作map-我需要的k，value不需要
    i := 0
    for k, _ := range r {
        sortKey[i] = k
        i++
    }
    fmt.Println(sortKey)

}

map[]
map[]
map[]
map[]
map[1:ok]
ok
ok

aaa true
--------------迭代-----------------
map[1:ok1 2:ok2]
map[1:ok1 2:ok2]
map[1:ok1 2:ok2]
map[1:ok1 2:ok2]
map[1:ok1 2:ok2]
[map[] map[] map[] map[] map[]]
---------遍历切片类型的map集合,相当于foreach---------
map[1:aaaaaa 2:aaaddaaa]
map[1:aaaaaa 2:aaaddaaa]
map[1:aaaaaa 2:aaaddaaa]
map[1:aaaaaa 2:aaaddaaa]
map[2:aaaddaaa 1:aaaaaa]
[map[1:aaaaaa 2:aaaddaaa] map[1:aaaaaa 2:aaaddaaa] map[1:aaaaaa 2:aaaddaaa] map[1:aaaaaa 2:aaaddaaa] map[1:aaaaaa 2:aaaddaaa]]
---------遍历map的键---------
[1 2 4]