How to dynamically build query filters - go

Question

I'm and using Go to setup my own API. I'm kind of stuck right now because of how I wrote the code to dynamically create/apply the query filter. It works but I'm wondering if there is a better way to do the scenario below.
For example, I have a search page with check boxes (1 for email and 1 for name) to narrow the search.
// 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
}
}
This is what I got so far and I think there is a better way to do this:
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
}
Is there a better way to do this instead of creating long condition?

Answer 1

Here is the reflection version of it. Basically it enumerates fields, gets the value and field names to build an array of string based on them. Please not that i'm not well experienced it might also require some improvements.
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)
}
Here is the playground

Answer 2

I would suggest to refactor your filter logic as mentioned below:
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)
}