CODEWITHSUNDEEP
go
under5hell
under5hell

Reputation: 997

Exclude empty fields from struct iteration

I have a struct that will get its value from user input. Now I want to extract only field names that have associated values. Fields with a nil value should not be returned. How can I do that?

Here’s my code:

package main


import "fmt"
import "reflect"

type Users struct {
    Name string
    Password string
}


func main(){
    u := Users{"Robert", ""}

    val := reflect.ValueOf(u)


    for i := 0; i < val.NumField(); i++ {

        fmt.Println(val.Type().Field(i).Name)

    }


}

Current Result:

Name
Password

Expected result:

Name

Upvotes: 0

Views: 2483

Answers (2)

under5hell
under5hell

Reputation: 997

I think I found a solution. Case closed. :)

import "fmt"
import "reflect"

type Users struct {
    Name string
    Password string
}


func main(){
    u := Users{"robert", ""}

    val := reflect.ValueOf(u)

    var fFields []string

    for i := 0; i < val.NumField(); i++ {
    f := val.Field(i)

    if f.Interface() != "" {
        fFields = append(fFields, val.Type().Field(i).Name)
    }

    }

   fmt.Println(fFields)
}

http://play.golang.org/p/QVIJaNXGQB

Upvotes: 0

user4122236
user4122236

Reputation:

You need to write a function to check for empty:

func empty(v reflect.Value) bool {
    switch v.Kind() {
    case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
        return v.Int() == 0
    case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
        return v.Uint() == 0
    case reflect.String:
        return v.String() == ""
    case reflect.Ptr, reflect.Slice, reflect.Map, reflect.Interface, reflect.Chan:
        return v.IsNil()
    case reflect.Bool:
        return !v.Bool()
    }
    return false
}

playground example.

Upvotes: 5

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