Go 语言中映射（Map）使用场景小结

// 创建一个存储 HTTP 状态码的映射
statusCodes := map[int]string{
    200: "OK",
    404: "Not Found",
    500: "Internal Server Error",
}

// 添加或修改
statusCodes[301] = "Moved Permanently"

// 查询（使用 "comma, ok" idiom 进行安全查询）
code := 404
status, ok := statusCodes[code]
if ok {
    fmt.Printf("Status for code %d is: %s\n", code, status)
} else {
    fmt.Printf("No status found for code %d\n", code)
}

// 创建一个集合来存储唯一的标签
tags := make(map[string]struct{})

// 添加元素
tags["go"] = struct{}{}
tags["web"] = struct{}{}
tags["go"] = struct{}{} // 重复添加，但集合大小不变

// 判断元素是否存在
if _, ok := tags["go"]; ok {
    fmt.Println("'go' tag exists.")
}

fmt.Println("Total unique tags:", len(tags)) // 输出 2

import "encoding/json"

jsonString := `{"name": "Alice", "age": 30, "is_active": true, "skills": ["Go", "PHP"]}`

var data map[string]interface{}

// 将 JSON 字符串解码到 map 中
json.Unmarshal([]byte(jsonString), &data)

// 现在可以动态访问数据了
name := data["name"].(string) // 需要类型断言
age := data["age"].(float64)  // JSON 数字默认解码为 float64
skills := data["skills"].([]interface{})

fmt.Printf("Name: %s, Age: %f, Skill1: %s\n", name, age, skills[0].(string))

type Employee struct {
    ID         int
    Name       string
    Department string
}

employees := []Employee{
    {1, "Alice", "Engineering"},
    {2, "Bob", "Sales"},
    {3, "Charlie", "Engineering"},
}

// 创建一个映射用于分组
employeesByDept := make(map[string][]Employee)

// 遍历员工切片，进行分组
for _, emp := range employees {
    employeesByDept[emp.Department] = append(employeesByDept[emp.Department], emp)
}

// 现在可以轻松访问特定部门的所有员工
fmt.Println("Engineering Dept:", employeesByDept["Engineering"])

import "sync"

// 一个带有读写锁保护的并发安全缓存
type Cache struct {
    mu   sync.RWMutex
    data map[string]interface{}
}

func (c *Cache) Get(key string) (interface{}, bool) {
    c.mu.RLock()         // 加读锁
    defer c.mu.RUnlock() // 函数结束时解锁
    val, ok := c.data[key]
    return val, ok
}

func (c *Cache) Set(key string, value interface{}) {
    c.mu.Lock()         // 加写锁
    defer c.mu.Unlock() // 函数结束时解锁
    c.data[key] = value
}

docs := map[int]string{
    1: "go is a programming language",
    2: "php is also a programming language",
    3: "go and php are popular",
}

// 创建倒排索引
index := make(map[string][]int)

for docID, content := range docs {
    words := strings.Fields(content) // 按空格分词
    for _, word := range words {
        index[word] = append(index[word], docID)
    }
}

// 现在可以快速查找包含 "go" 的所有文档 ID
fmt.Println("Docs containing 'go':", index["go"]) // 输出 [1 3]
fmt.Println("Docs containing 'language':", index["language"]) // 输出 [1 2]