kataras/iris · error

simple dates: scan: invalid type of: %T

Error message

simple dates: scan: invalid type of: %T

What it means

SimpleDates.Scan scans a JSON array of dates stored in a single column (json/jsonb). It accepts only []byte or string src and then json.Unmarshals into the slice; any other driver type (int64, time.Time, float64, etc.) is rejected with "simple dates: scan: invalid type of: %T".

Source

Thrown at x/jsonx/simple_date.go:224

	}

	return list
}

// Scan completes the pg and native sql driver.Scanner interface.
func (t *SimpleDates) Scan(src any) error {
	if src == nil {
		return nil
	}

	var data []byte
	switch v := src.(type) {
	case []byte:
		data = v
	case string:
		data = []byte(v)
	default:
		return fmt.Errorf("simple dates: scan: invalid type of: %T", src)
	}

	err := json.Unmarshal(data, t)
	return err
}

// Value completes the pg and native sql driver.Valuer interface.
func (t SimpleDates) Value() (driver.Value, error) {
	if len(t) == 0 {
		return nil, nil
	}

	b, err := json.Marshal(t)
	return b, err
}

// Contains reports if the "date" exists inside "t".
func (t SimpleDates) Contains(date SimpleDate) bool {

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Store the list as a JSON array in a json/jsonb (or TEXT) column so src is []byte/string.
2. Fix struct/query so the JSON column is selected into the SimpleDates field.
3. If the source is date[], scan into []time.Time and build jsonx.SimpleDates manually.

Example fix

// before: column date[] scanned into SimpleDates -> error
// after: column jsonb containing ["2024-01-01","2024-01-02"]
var dates jsonx.SimpleDates
rows.Scan(&dates)

func canScanSimpleDates(src any) bool {
	switch src.(type) {
	case []byte, string:
		return true
	}
	return false
}

func knownSimpleDatesSrc(src any) bool {
	switch src.(type) {
	case []byte, string:
		return true
	default:
		return false
	}
}

var dates jsonx.SimpleDates
if err := rows.Scan(&dates); err != nil {
	if strings.HasPrefix(err.Error(), "simple dates: scan: invalid type") {
		return fmt.Errorf("column must be json/text containing a JSON date array: %w", err)
	}
	return err
}

When it happens

Trigger: Scanning a non-text/non-json column (e.g. TIMESTAMP, BIGINT, or an ARRAY type the driver decodes to something else) into *jsonx.SimpleDates; the column decode yields time.Time or int64 instead of bytes/string.

Common situations: Wrong column mapped to a SimpleDates field; DB array types like date[] instead of a JSON array column; driver decoding jsonb into a native type rather than bytes.

Related errors

• KitchenTime: unknown type of: %T
• SimpleDate: unknown type of: %T
• kitchen time: convert to time notation first: %w
• %s: %w
• %w: example: %s

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/b0996924b973b7bf. Report an issue: GitHub.