Golang如何用 reflect.Type 获取类型信息_Golang reflect 类型与结构体操作实践

package main

import (
    "fmt"
    "reflect"
)

func main() {
    var name string = "Tom"
    t := reflect.TypeOf(name)
    fmt.Println(t) // 输出: string
}

type User struct {
    Name string
    Age  int
}

user := User{}
t := reflect.TypeOf(user)
fmt.Println(t) // 输出: main.User

type Product struct {
    ID    int    `json:"id"`
    Title string `json:"title" validate:"required"`
    Price float64
}

prod := Product{}
t := reflect.TypeOf(prod)

for i := 0; i < t.NumField(); i++ {
    field := t.Field(i)
    fmt.Printf("字段名: %s\n", field.Name)
    fmt.Printf("类型: %v\n", field.Type)
    fmt.Printf("json 标签: %s\n", field.Tag.Get("json"))
    fmt.Printf("校验标签: %s\n", field.Tag.Get("validate"))
}

字段名: ID
类型: int
json 标签: id
校验标签: 
字段名: Title
类型: string
json 标签: title
校验标签: required
字段名: Price
类型: float64
json 标签: 
校验标签: 

func printStructFields(v interface{}) {
    t := reflect.TypeOf(v)

    // 如果是指针，取其指向的类型
    if t.Kind() == reflect.Ptr {
        t = t.Elem()
    }

    // 确保是结构体
    if t.Kind() != reflect.Struct {
        fmt.Println("输入不是结构体")
        return
    }

    for i := 0; i < t.NumField(); i++ {
        field := t.Field(i)
        fmt.Printf("%s (%s)\n", field.Name, field.Type)
    }
}

// 调用示例
user := &User{Name: "Alice", Age: 25}
printStructFields(user) // 正常输出字段

func buildColumns(v interface{}) []string {
    var columns []string
    t := reflect.TypeOf(v)

    if t.Kind() == reflect.Ptr {
        t = t.Elem()
    }

    for i := 0; i < t.NumField(); i++ {
        field := t.Field(i)
        dbTag := field.Tag.Get("db")
        if dbTag == "" || dbTag == "-" {
            continue
        }
        columns = append(columns, dbTag)
    }
    return columns
}

type Order struct {
    ID     int     `db:"order_id"`
    Amount float64 `db:"amount"`
    Status string  `db:"-"`
}

// 使用
cols := buildColumns(Order{})
fmt.Println(cols) // 输出: [order_id amount]