Golang Mapper.TraversalsByName方法代码示例

// private interface to generate a list of interfaces from a given struct
// type, given a list of names to pull out of the struct.  Used by public
// BindStruct interface.
func bindArgs(names []string, arg interface{}, m *reflectx.Mapper) ([]interface{}, error) {
	arglist := make([]interface{}, 0, len(names))

	// grab the indirected value of arg
	v := reflect.ValueOf(arg)
	for v = reflect.ValueOf(arg); v.Kind() == reflect.Ptr; {
		v = v.Elem()
	}

	fields := m.TraversalsByName(v.Type(), names)
	for i, t := range fields {
		if len(t) == 0 {
			return arglist, fmt.Errorf("could not find name %s in %#v", names[i], arg)
		}
		val := reflectx.FieldByIndexesReadOnly(v, t)
		arglist = append(arglist, val.Interface())
	}

	return arglist, nil
}

// scanAll scans all rows into a destination, which must be a slice of any
// type.  If the destination slice type is a Struct, then StructScan will be
// used on each row.  If the destination is some other kind of base type, then
// each row must only have one column which can scan into that type.  This
// allows you to do something like:
//
//    rows, _ := db.Query("select id from people;")
//    var ids []int
//    scanAll(rows, &ids, false)
//
// and ids will be a list of the id results.  I realize that this is a desirable
// interface to expose to users, but for now it will only be exposed via changes
// to `Get` and `Select`.  The reason that this has been implemented like this is
// this is the only way to not duplicate reflect work in the new API while
// maintaining backwards compatibility.
func scanAll(rows rowsi, dest interface{}, structOnly bool) error {
	var v, vp reflect.Value

	value := reflect.ValueOf(dest)

	// json.Unmarshal returns errors for these
	if value.Kind() != reflect.Ptr {
		return errors.New("must pass a pointer, not a value, to StructScan destination")
	}
	if value.IsNil() {
		return errors.New("nil pointer passed to StructScan destination")
	}
	direct := reflect.Indirect(value)

	slice, err := baseType(value.Type(), reflect.Slice)
	if err != nil {
		return err
	}

	isPtr := slice.Elem().Kind() == reflect.Ptr
	base := reflectx.Deref(slice.Elem())
	scannable := isScannable(base)

	if structOnly && scannable {
		return structOnlyError(base)
	}

	columns, err := rows.Columns()
	if err != nil {
		return err
	}

	// if it's a base type make sure it only has 1 column;  if not return an error
	if scannable && len(columns) > 1 {
		return fmt.Errorf("non-struct dest type %s with >1 columns (%d)", base.Kind(), len(columns))
	}

	if !scannable {
		var values []interface{}
		var m *reflectx.Mapper

		switch rows.(type) {
		case *Rows:
			m = rows.(*Rows).Mapper
		default:
			m = mapper()
		}

		fields := m.TraversalsByName(base, columns)
		// if we are not unsafe and are missing fields, return an error
		if f, err := missingFields(fields); err != nil && !isUnsafe(rows) {
			return fmt.Errorf("missing destination name %s", columns[f])
		}
		values = make([]interface{}, len(columns))

		for rows.Next() {
			// create a new struct type (which returns PtrTo) and indirect it
			vp = reflect.New(base)
			v = reflect.Indirect(vp)

			err = fieldsByTraversal(v, fields, values, true)

			// scan into the struct field pointers and append to our results
			err = rows.Scan(values...)
			if err != nil {
				return err
			}

			if isPtr {
				direct.Set(reflect.Append(direct, vp))
			} else {
				direct.Set(reflect.Append(direct, v))
			}
		}
	} else {
		for rows.Next() {
			vp = reflect.New(base)
			err = rows.Scan(vp.Interface())
			// append
			if isPtr {
				direct.Set(reflect.Append(direct, vp))
			} else {
				direct.Set(reflect.Append(direct, reflect.Indirect(vp)))
			}
		}
//.........这里部分代码省略.........

// scanAll scans all rows into a destination, which must be a slice of any
// type.  If the destination slice type is a Struct, then StructScan will be
// used on each row.  If the destination is some other kind of base type, then
// each row must only have one column which can scan into that type.  This
// allows you to do something like:
//
//    rows, _ := db.Query("select id from people;")
//    var ids []int
//    scanAll(rows, &ids, false)
//
// and ids will be a list of the id results.  I realize that this is a desirable
// interface to expose to users, but for now it will only be exposed via changes
// to `Get` and `Select`.  The reason that this has been implemented like this is
// this is the only way to not duplicate reflect work in the new API while
// maintaining backwards compatibility.
func scanAll(rows rowsi, dest interface{}, structOnly bool) error {
	var v, vp reflect.Value

	value := reflect.ValueOf(dest)

	// json.Unmarshal returns errors for these
	if value.Kind() != reflect.Ptr {
		return errors.New("must pass a pointer, not a value, to StructScan destination")
	}
	if value.IsNil() {
		return errors.New("nil pointer passed to StructScan destination")
	}
	direct := reflect.Indirect(value)

	slice, err := baseType(value.Type(), reflect.Slice)
	if err != nil {
		return err
	}

	isPtr := slice.Elem().Kind() == reflect.Ptr
	base := reflectx.Deref(slice.Elem())
	isStruct := base.Kind() == reflect.Struct
	// check if a pointer to the slice type implements sql.Scanner; if it does, we
	// will treat this as a base type slice rather than a struct slice;  eg, we will
	// treat []sql.NullString as a single row rather than a struct with 2 scan targets.
	isScanner := reflect.PtrTo(base).Implements(_scannerInterface)

	// if we must have a struct and the base type isn't a struct, return an error.
	// this maintains API compatibility for StructScan, which is only important
	// because StructScan should involve structs and it feels gross to add more
	// weird junk to it.
	if structOnly {
		if !isStruct {
			return fmt.Errorf("expected %s but got %s", reflect.Struct, base.Kind())
		}
		if isScanner {
			return fmt.Errorf("structscan expects a struct dest but the provided struct type %s implements scanner", base.Name())
		}
	}

	columns, err := rows.Columns()
	if err != nil {
		return err
	}

	// if it's a base type make sure it only has 1 column;  if not return an error
	if !isStruct && len(columns) > 1 {
		return fmt.Errorf("non-struct dest type %s with >1 columns (%d)", base.Kind(), len(columns))
	}

	if isStruct && !isScanner {
		var values []interface{}
		var m *reflectx.Mapper

		switch rows.(type) {
		case *Rows:
			m = rows.(*Rows).Mapper
		default:
			m = mapper()
		}

		fields := m.TraversalsByName(base, columns)
		// if we are not unsafe and are missing fields, return an error
		if f, err := missingFields(fields); err != nil && !isUnsafe(rows) {
			return fmt.Errorf("missing destination name %s", columns[f])
		}
		values = make([]interface{}, len(columns))

		for rows.Next() {
			// create a new struct type (which returns PtrTo) and indirect it
			vp = reflect.New(base)
			v = reflect.Indirect(vp)

			err = fieldsByTraversal(v, fields, values, true)

			// scan into the struct field pointers and append to our results
			err = rows.Scan(values...)
			if err != nil {
				return err
			}

			if isPtr {
				direct.Set(reflect.Append(direct, vp))
			} else {
				direct.Set(reflect.Append(direct, v))
//.........这里部分代码省略.........