如何动态构建查询过滤器

Question

我正在使用 Go 来设置我自己的 API。我现在有点卡住了，因为我如何编写代码来动态创建/应用查询过滤器。它有效，但我想知道是否有更好的方法来完成以下场景。

例如，我有一个带有复选框的搜索页面（1 个用于电子邮件，1 个用于名称）以缩小搜索范围。

// If I checked the email, the query would be like this
query findOne() {
  user(func: type(user)) @filter(eq(email, "john.doe@email.com")) {
    name
    email
    age
    home_address
  }
}

// If name checkedbox is also checked, it would be like this
query findOne() {
  user(func: type(user)) @filter(eq(email, "john") OR eq(name, "john")) {
    name
    email
    age
    home_address
  }
}

这是我目前得到的，我认为有更好的方法来做到这一点：

func (s *Service) GetUser(email, name string) (*Users, error) {
    c := db.NewClient()
    defer db.Close()
    var u Users
    var filter string

    if email != "" && mobileNumber != "" {
      filter = fmt.Sprintf(`eq(email, "%s") OR eq(mobileNumber, "%s")`, email, mobileNumber)
    } else if email != "" && mobileNumber == "" {
      filter = fmt.Sprintf(`eq(email, "%s")`, email)
    } else if email == "" && mobileNumber != "" {
      filter = fmt.Sprintf(`eq(mobileNumber, "%s")`, mobileNumber)
    }

    q := fmt.Sprintf(`query findOne() {
        users(func: type("user")) @filter(%s) {
            name
            email
            home_address
            contact_number
        }
    }`, filter)
    ctx := context.Background()
    res, err := c.NewTxn().Query(ctx, q)
    if err != nil {
        return nil, err
    }
    if err = json.Unmarshal(res.Json, &u); err != nil {
        return nil, err
    }
    return &u, nil
}

有没有更好的方法来代替创建长条件？

Answer 1

这是它的反射版本。基本上它枚举字段，获取值和字段名称以基于它们构建字符串数组。请注意，我经验不足，可能还需要一些改进。

import (
    "fmt"
    "reflect"
    "strings"
)

type User struct {
    Id       int    
    FullName string 
    Phone    string 
    Mail     string 
}

func main() {
    u := &User{Id: 10, FullName: "John", Mail: "john@mail"}
    u2 := struct {
        id   int
        name string
    }{10, "john"};
   // inline struct
    q := getQuery(&u2, "OR")
    fmt.Println(q)

   // typed struct
    q = getQuery(u, "AND")
    fmt.Println(q)
}

func getQuery(target interface{}, join string) string {
    var filters []string
    val := reflect.ValueOf(target).Elem()

    for i := 0; i < val.NumField(); i++ {
        value := val.Field(i)
        s :=fmt.Sprintf("%v",value);
        // this little trick is to check if it is an empty value
        // so don't generate empty condition expressions
        if s == "" {
             continue
        }
        fieldType := val.Type().Field(i)
        filters = append(filters, fmt.Sprintf(" eq(%s, %v) ", fieldType.Name, value))
    }

    return strings.Join(filters, join)
}

这里是playground

Answer 2

我建议重构您的过滤器逻辑，如下所述：

package main

import (
    "fmt"
    "strings"
)

func getQuery(key, val string, filters *[]string) {
    if val != "" {
        *filters = append(*filters, fmt.Sprintf(`eq("%s", "%s")`, key, val))
    }
}
func main() {
    var filters []string
    email := "demo@demo.com"
    mobileNumber := "123456789"

    getQuery("email", email, &filters)
    getQuery("mobileNumber", mobileNumber, &filters)
    filter := strings.Join(filters, " OR ")
    fmt.Println(filter)
}