marshal

Example: marshal

Demonstrates SLogMarshaler — the interface for types that want full control over their log representation, analogous to json.Marshaler.

type SLogMarshaler interface {
    MarshalSLog() []slog.Attr
}

Any type implementing this interface is handled automatically by ToAttrs, both at the top level and as a nested field inside another struct.

Run

go run github.com/silvercory/slog-schema/example/marshal

Output

level=INFO msg="order created" id=ord_abc123 total.amount="49.99 GBP" status.code=201 status.label=Created labels.0=new labels.1=priority labels.2=gift
level=INFO msg=payment amount="9.00 USD"

Types in this example

Money — formats a monetary amount as a human-readable string rather than exposing raw integer fields:

func (m Money) MarshalSLog() []slog.Attr {
    return []slog.Attr{
        slog.String("amount", fmt.Sprintf("%d.%02d %s", m.Units, m.Cents, m.Currency)),
    }
}

Status — maps an integer HTTP status code to both the numeric value and a human-readable label:

func (s Status) MarshalSLog() []slog.Attr {
    return []slog.Attr{
        slog.Int("code", int(s)),
        slog.String("label", name),
    }
}

Tags — collapses a string slice into a single comma-separated value instead of indexed group entries:

func (t Tags) MarshalSLog() []slog.Attr {
    return []slog.Attr{
        slog.String("tags", strings.Join(t, ",")),
    }
}