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super_scan.go
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super_scan.go
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package sqlx
import (
"database/sql"
"reflect"
"strings"
"github.com/go-courier/sqlx/v2/builder"
"github.com/go-courier/sqlx/v2/nullable"
)
type ScanIterator interface {
// new a ptr value for scan
New() interface{}
// for receive scanned value
Next(v interface{}) error
}
func Scan(rows *sql.Rows, v interface{}) error {
if rows == nil {
return nil
}
defer rows.Close()
modelScanner, err := newModelScanner(v)
if err != nil {
return err
}
// simple value scan
for rows.Next() {
if modelScanner.direct {
if scanErr := rows.Scan(modelScanner.v); scanErr != nil {
return scanErr
}
continue
}
rv, err := modelScanner.New()
if err != nil {
return err
}
if scanErr := scanStruct(rows, rv); scanErr != nil {
return scanErr
}
if err := modelScanner.Next(rv); err != nil {
return err
}
}
if !modelScanner.direct && !modelScanner.isSlice && modelScanner.scanIterator == nil && modelScanner.count == 0 {
return NewSqlError(sqlErrTypeNotFound, "record is not found")
}
if err := rows.Err(); err != nil {
return err
}
// Make sure the query can be processed to completion with no errors.
if err := rows.Close(); err != nil {
return err
}
return nil
}
func newModelScanner(v interface{}) (*modelScanner, error) {
si := &modelScanner{v: v}
if _, ok := v.(sql.Scanner); ok {
si.direct = true
} else if scanIterator, ok := v.(ScanIterator); ok {
si.scanIterator = scanIterator
} else {
modelType := reflect.TypeOf(v)
if modelType.Kind() != reflect.Ptr {
return nil, NewSqlError(sqlErrTypeInvalidScanTarget, "can not scan to a none pointer variable")
}
si.modelType = modelType.Elem()
if si.modelType.Kind() == reflect.Slice {
si.modelType = si.modelType.Elem()
si.isSlice = true
}
si.rv = reflect.Indirect(reflect.ValueOf(v))
si.direct = si.modelType.Kind() != reflect.Struct
}
return si, nil
}
type modelScanner struct {
v interface{}
rv reflect.Value
direct bool
isSlice bool
count int
modelType reflect.Type
scanIterator ScanIterator
}
func (s *modelScanner) New() (reflect.Value, error) {
if s.scanIterator != nil {
rv := reflect.ValueOf(s.scanIterator.New())
if rv.Kind() != reflect.Ptr {
return reflect.Value{}, NewSqlError(sqlErrTypeInvalidScanTarget, "can not scan to a none pointer variable")
}
return rv.Elem(), nil
}
if s.isSlice {
return reflect.New(s.modelType).Elem(), nil
}
return s.rv, nil
}
func (s *modelScanner) Next(rv reflect.Value) error {
s.count++
if s.scanIterator != nil {
return s.scanIterator.Next(rv.Addr().Interface())
}
if s.isSlice {
s.rv.Set(reflect.Append(s.rv, rv))
return nil
}
s.rv.Set(rv)
return nil
}
func scanStruct(rows *sql.Rows, rv reflect.Value) error {
columns, err := rows.Columns()
if err != nil {
return err
}
n := len(columns)
dest := make([]interface{}, n)
columnIndexes := map[string]int{}
p := placeholder()
for i, name := range columns {
columnIndexes[strings.ToLower(name)] = i
dest[i] = p
}
builder.ForEachStructFieldValue(rv, func(structFieldValue reflect.Value, structField reflect.StructField, columnName string, tagValue string) {
if i, ok := columnIndexes[columnName]; ok && i > -1 {
dest[i] = nullable.NewNullIgnoreScanner(structFieldValue.Addr().Interface())
}
})
return rows.Scan(dest...)
}
func placeholder() *emptyScanner {
p := emptyScanner(0)
return &p
}
type emptyScanner int
func (e *emptyScanner) Scan(value interface{}) error {
return nil
}