utils/dbtool/dbtool.go

package dbtool

import (
	"database/sql"
	"errors"
	"reflect"
	"strconv"
	"strings"
	"time"
)

// ScanToStruct - scan query rows to struct
func ScanToStruct(rows *sql.Rows, ss interface{}) (ok bool, err error) {
	data, err := ResultToMap(rows)
	if err != nil {
		return false, err
	}
	if len(data) == 0 {
		return false, nil
	}
	err = MapToStruct(data[0], ss)
	if err != nil {
		return false, err
	}
	return true, nil
}

// ScanToStructAll -
func ScanToStructAll(rows *sql.Rows, ss interface{}) error {
	sliceVal := reflect.Indirect(reflect.ValueOf(ss))
	if sliceVal.Kind() != reflect.Slice {
		return errors.New("need a pointer to a slice ")
	}
	vt := sliceVal.Type().Elem()
	if vt.Kind() != reflect.Struct {
		return errors.New("need struct slice")
	}

	data, err := ResultToMap(rows)
	if err != nil {
		return err
	}

	for i := range data {
		tmp := reflect.New(vt)
		iface := tmp.Interface()
		err = MapToStruct(data[i], iface)
		if err != nil {
			return err
		}
		sliceVal.Set(reflect.Append(sliceVal, reflect.ValueOf(iface).Elem()))
	}

	return nil
}

// ResultToMap -
func ResultToMap(r *sql.Rows) ([]map[string]interface{}, error) {
	result := make([]map[string]interface{}, 0)
	cols, err := r.Columns()
	if err != nil {
		return nil, err
	}
	vals := make([]sql.RawBytes, len(cols))
	scans := make([]interface{}, len(vals))

	for i := range vals {
		scans[i] = &vals[i]
	}

	for r.Next() {
		tmp := make(map[string]interface{})
		err := r.Scan(scans...)
		if err != nil {
			return nil, err
		}
		for i, v := range vals {
			tmp[cols[i]] = v
			vals[i] = nil
		}
		result = append(result, tmp)
	}

	return result, nil
}

// MapToStruct -
func MapToStruct(data map[string]interface{}, out interface{}) error {
	ss := reflect.ValueOf(out).Elem()
	for i := 0; i < ss.NumField(); i++ {
		tag := ss.Type().Field(i).Tag.Get("sql")
		name := ss.Type().Field(i).Name
		fname := strings.ToLower(name)
		if len(tag) > 0 {
			fname = tag
		}

		if fname == "-" {
			continue
		}

		d, ok := data[fname]
		if !ok {
			continue
		}

		switch ss.Field(i).Interface().(type) {
		case string:
			ss.Field(i).SetString(string(d.(sql.RawBytes)))
		case int, int8, int16, int32, int64:
			str := string(d.(sql.RawBytes))
			tmpi, err := strconv.ParseInt(str, 10, 64)
			if err != nil {
				return err
			}
			ss.Field(i).SetInt(tmpi)
		case uint, uint8, uint16, uint32, uint64:
			str := string(d.(sql.RawBytes))
			tmpi, err := strconv.ParseUint(str, 10, 64)
			if err != nil {
				return err
			}
			ss.Field(i).SetUint(tmpi)
		case bool:
			str := string(d.(sql.RawBytes))
			tmpb, err := strconv.ParseBool(str)
			if err != nil {
				return err
			}
			ss.Field(i).SetBool(tmpb)
		case float32, float64:
			str := string(d.(sql.RawBytes))
			tmpf, err := strconv.ParseFloat(str, 64)
			if err != nil {
				return err
			}
			ss.Field(i).SetFloat(tmpf)
		case time.Time:
			str := string(d.(sql.RawBytes))
			t, err := time.Parse(time.RFC3339, str)
			if err != nil {
				return err
			}
			ss.Field(i).Set(reflect.ValueOf(t))
		default:
			str := string(d.(sql.RawBytes))
			ss.Field(i).Set(reflect.ValueOf(str))
		}
	}

	return nil
}