Golang-Map

// 初始化定义map[KeyType]ValueType// KeyType:表示键的类型。map可以嵌套map，可以是key 也是是value// ValueType:表示键对应的值的类型。map类型的变量默认初始值为nil，需要使用make()函数来分配内存。语法为：make(map[KeyType]ValueType, [cap])// 赋值定义map[KeyType]ValueType{
  key1:value1
  key2:value2
  key4:value3
}

package mainimport "fmt"func main() {
    a := make(map[string]string)
    a["name"] = "Payne"
    a["sex"] = "male"
    a["year"] = "20"
    fmt.Println("a:", a)               // a: map[name:Payne sex:male year:20]
    fmt.Println("a['sex']:", a["sex"]) // a['sex']: male
    fmt.Printf("Type of a:%T\n", a)      // Type of a:map[string]string

    b := map[string]string{        "Name": "Tim",        "Sex":  "male",        "Year": "20",
    }
    fmt.Println("b:", b)               // b: map[Name:Tim Sex:male Year:20]
    fmt.Println("b['sex']:", b["Sex"]) // b['sex']: male
    fmt.Printf("Type of b:%T", b)   // Type of b:map[string]string}

value, ok := map[key]// 其中 value可以为任意接受值。而 ok 必须写

package mainimport "fmt"func main() {
    c := map[string]string{        "name1": "Tom",        "name2": "Tim",        "name3": "Payne",        "name4": "John",
    }    // 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
    value, ok := c["name1"]
    fmt.Println(value, ok)     // Tom true

    value, ok := c["name5"]
    fmt.Println(value, ok)     // false

  if ok {
    fmt.Println(value)             // Tom
  } else {
        fmt.Println("nil")
    }
}

// 遍历
    d := map[string]string{        "name1": "Tom",        "name2": "Tim",        "name3": "Payne",        "name4": "John",
    }    // 只遍历key
    for d := range d {
        fmt.Print(d + ",")  // name1,name2,name3,name4,
    }
    fmt.Printf("\n")    // 只遍历value
    for _, v := range d {
        fmt.Print(v + ",")  // Tom,Tim,Payne,John,
    }
    fmt.Printf("\n")    // 遍历key value
    for k, v := range d {
        fmt.Print(k, ":", v, " ")   // name2:Tim name3:Payne name4:John name1:Tom
    }

delete(map, key)// map:表示要删除键值对的map// key:表示要删除的键值对

    f := map[string]string{        "name1": "Tom",        "name2": "Tim",        "name3": "Payne",        "name4": "John",
    }
    v1, ok := f["name1"]
    fmt.Println(v1, ok)  // Tom true
    delete(f, "name1")
    v2, ok := f["name1"]
    fmt.Println(v2, ok)  // false

func main() {
  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"] = "payne"
    mapSlice[0]["password"] = "123456"
    mapSlice[0]["address"] = "cs"
    for index, value := range mapSlice {
        fmt.Printf("index:%d value:%v\n", index, value)
    }
}// index:0 value:map[]// index:1 value:map[]// index:2 value:map[]// after init// index:0 value:map[address:cs name:payne password:123456]// index:1 value:map[]// index:2 value:map[]

func main() {
  sliceMap := make(map[string][]string, 3)
    fmt.Println(sliceMap)
    fmt.Println("after init")
    key := "中国"
    value, ok := sliceMap[key]    if !ok {
        value = make([]string, 0, 2)
    }
    value = append(value, "北京", "上海")
    sliceMap[key] = value
    fmt.Println(sliceMap)
}// map[]// after init// map[中国:[北京 上海]]