webutil/formscanner.go

@@ -8,9 +8,17 @@ import (
 
 var ErrUnsupportedType = errors.New("unsupported type")
 
+// FormScanFunc is a custom form scanner that can be used to scan custom
+// types using the form scanner.
+//
+// It returns true if it recognizes the type of val, and an error if scanning
+// fails.
+type FormScanFunc func(form url.Values, name string, val any) (bool, error)
+
 type FormScanner struct {
-	form url.Values
-	err  error
+	form     url.Values
+	err      error
+	ScanFunc FormScanFunc
 }
 
 func NewFormScanner(form url.Values) *FormScanner {
@@ -22,6 +30,13 @@ func (s *FormScanner) Scan(name string, val any) *FormScanner {
 		return s
 	}
 
+	if s.ScanFunc != nil {
+		if ok, err := s.ScanFunc(s.form, name, val); ok {
+			s.err = err
+			return s
+		}
+	}
+
 	switch v := val.(type) {
 	case *bool:
 		*v = s.form.Has(name)
@@ -37,7 +52,3 @@ func (s *FormScanner) Scan(name string, val any) *FormScanner {
 func (s *FormScanner) Error() error {
 	return s.err
 }
-
-func (s *FormScanner) SetError(err error) {
-	s.err = err
-}