Question

都在代码里自己看吧

package main

import (
    "net/http"
    "reflect"
    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
    "gopkg.in/go-playground/validator.v8"
)

/*
    对绑定解析到结构体上的参数，自定义验证功能
    比如我们要对 name 字段做校验，要不能为空，并且不等于 admin ，类似这种需求，就无法 binding 现成的方法
    需要我们自己验证方法才能实现 官网示例（https://godoc.org/gopkg.in/go-playground/validator.v8#hdr-Custom_Functions）
    这里需要下载引入下 gopkg.in/go-playground/validator.v8
*/
type Person struct {
    Age int `form:"age" binding:"required,gt=10"`
    // 2、在参数 binding 上使用自定义的校验方法函数注册时候的名称
    Name    string `form:"name" binding:"NotNullAndAdmin"`
    Address string `form:"address" binding:"required"`
}

// 1、自定义的校验方法
func nameNotNullAndAdmin(v *validator.Validate, topStruct reflect.Value, currentStructOrField reflect.Value, field reflect.Value, fieldType reflect.Type, fieldKind reflect.Kind, param string) bool {

    if value, ok := field.Interface().(string); ok {
        // 字段不能为空，并且不等于  admin
        return value != "" && !("5lmh" == value)
    }

    return true
}

func main() {
    r := gin.Default()

    // 3、将我们自定义的校验方法注册到 validator中
    if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
        // 这里的 key 和 fn 可以不一样最终在 struct 使用的是 key
        v.RegisterValidation("NotNullAndAdmin", nameNotNullAndAdmin)
    }

    /*
        curl -X GET "http://127.0.0.1:8080/testing?name=&age=12&address=beijing"
        curl -X GET "http://127.0.0.1:8080/testing?name=lmh&age=12&address=beijing"
        curl -X GET "http://127.0.0.1:8080/testing?name=adz&age=12&address=beijing"
    */
    r.GET("/5lmh", func(c *gin.Context) {
        var person Person
        if e := c.ShouldBind(&person); e == nil {
            c.String(http.StatusOK, "%v", person)
        } else {
            c.String(http.StatusOK, "person bind err:%v", e.Error())
        }
    })
    r.Run()
}

示例2：

package main

import (
    "net/http"
    "reflect"
    "time"

    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
    "gopkg.in/go-playground/validator.v8"
)

// Booking contains binded and validated data.
type Booking struct {
    //定义一个预约的时间大于今天的时间
    CheckIn time.Time `form:"check_in" binding:"required,bookabledate" time_format:"2006-01-02"`
    //gtfield=CheckIn退出的时间大于预约的时间
    CheckOut time.Time `form:"check_out" binding:"required,gtfield=CheckIn" time_format:"2006-01-02"`
}

func bookableDate(
    v *validator.Validate, topStruct reflect.Value, currentStructOrField reflect.Value,
    field reflect.Value, fieldType reflect.Type, fieldKind reflect.Kind, param string,
) bool {
    //field.Interface().(time.Time)获取参数值并且转换为时间格式
    if date, ok := field.Interface().(time.Time); ok {
        today := time.Now()
        if today.Unix() > date.Unix() {
            return false
        }
    }
    return true
}

func main() {
    route := gin.Default()
    //注册验证
    if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
        //绑定第一个参数是验证的函数第二个参数是自定义的验证函数
        v.RegisterValidation("bookabledate", bookableDate)
    }

    route.GET("/5lmh", getBookable)
    route.Run()
}

func getBookable(c *gin.Context) {
    var b Booking
    if err := c.ShouldBindWith(&b, binding.Query); err == nil {
        c.JSON(http.StatusOK, gin.H{"message": "Booking dates are valid!"})
    } else {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
    }
}

// curl -X GET "http://localhost:8080/5lmh?check_in=2019-11-07&check_out=2019-11-20"
// curl -X GET "http://localhost:8080/5lmh?check_in=2019-09-07&check_out=2019-11-20"
// curl -X GET "http://localhost:8080/5lmh?check_in=2019-11-07&check_out=2019-11-01"