Golang reflect play

reflect.go

package main

import (
	"errors"
	"fmt"
	"os"
	"reflect"
	"strconv"
	"strings"
)

type Point struct {
	X uint64
	Y string
	Z int32
}

func ToStuct(row string, value interface{}) error {
	return toStruct(row, reflect.ValueOf(value).Elem())
}

func ToCSV(value interface{}) (string, error) {
	return toCSV(reflect.ValueOf(value).Elem())
}

func toStruct(row string, v reflect.Value) error {
	lexems := strings.Split(row, ",")

	if len(lexems) != v.NumField() {
		return errors.New("invalid amount of fields")
	}

	for i := 0; i < v.NumField(); i++ {
		fx := v.Field(i)
		switch fx.Kind() {
		case reflect.String:
			s, _ := strconv.Unquote(lexems[i])
			fx.SetString(s)
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			s, _ := strconv.ParseUint(lexems[i], 10, 64)
			fx.SetUint(s)
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			s, _ := strconv.ParseInt(lexems[i], 10, 64)
			fx.SetInt(s)
		}
	}

	return nil
}

func toCSV(v reflect.Value) (string, error) {
	str := strings.Builder{}

	for i := 0; i < v.NumField(); i++ {
		fx := v.Field(i)
		switch fx.Kind() {
		case reflect.String:
			s, _ := strconv.Unquote(strconv.Quote(fx.String()))
			str.WriteString(s)
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			str.WriteString(strconv.FormatUint(fx.Uint(), 10))
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			str.WriteString(strconv.FormatInt(fx.Int(), 10))
		}
		if i != v.NumField()-1 {
			str.WriteString(", ")
		}
	}

	return str.String(), nil
}

func main() {
	p := new(Point)
	err := ToStuct("1,\"hello\",112", p)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	fmt.Println(*p)

	res, err := ToCSV(p)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	fmt.Println(res)
}

tags.go

package main

import (
	"fmt"
	"net/http"
	"os"
	"reflect"
	"strconv"
)

func Unpack(r *http.Request, v interface{}) error {
	if err := r.ParseForm(); err != nil {
		return err
	}

	fields := make(map[string]reflect.Value)
	obj := reflect.ValueOf(v).Elem()
	for i := 0; i < obj.NumField(); i++ {
		fieldType := obj.Type().Field(i)
		tag := fieldType.Tag.Get("http")
		fields[tag] = obj.Field(i)
	}

	for name, values := range r.Form {
		f := fields[name]
		if !f.IsValid() {
			continue
		}

		for _, value := range values {
			switch f.Kind() {
			case reflect.Bool:
				res, err := strconv.ParseBool(value)
				if err != nil {
					return err
				}
				f.SetBool(res)
			}
			// TODO: other...
		}

	}

	return nil
}

func ExampleHandler(w http.ResponseWriter, r *http.Request) {
	var data struct {
		X bool `http:"x"`
	}

	err := Unpack(r, &data)
	if err != nil {
		http.Error(w, err.Error(), 400)
	}

	fmt.Fprintf(w, "Search %+v\n", data)
}

func main() {
	http.HandleFunc("/", ExampleHandler)

	err := http.ListenAndServe(":8080", nil)
	if err != nil {
		fmt.Fprint(os.Stderr, err)
	}
}