Trait tracing_subscriber::fmt::FormatFields

pub trait FormatFields<'writer> {
    fn format_fields<R: RecordFields>(
        &self,
        writer: &'writer mut dyn Write,
        fields: R
    ) -> Result;

    fn add_fields(
        &self,
        current: &'writer mut String,
        fields: &Record<'_>
    ) -> Result { ... }
}

A type that can format a set of fields to a fmt::Write.

FormatFields is primarily used in the context of FmtSubscriber. Each time a span or event with fields is recorded, the subscriber will format those fields with its associated FormatFields implementation.

Required Methods

fn format_fields<R: RecordFields>(
    &self,
    writer: &'writer mut dyn Write,
    fields: R
) -> Result

Format the provided fields to the provided writer, returning a result.

Provided Methods

fn add_fields(&self, current: &'writer mut String, fields: &Record<'_>) -> Result

Record additional field(s) on an existing span.

By default, this appends a space to the current set of fields if it is non-empty, and then calls self.format_fields. If different behavior is required, the default implementation of this method can be overridden.

Implementors

impl<'a> FormatFields<'a> for JsonFields

impl<'cx, 'writer, S, N> FormatFields<'writer> for FmtContext<'cx, S, N>where
    S: Subscriber + for<'lookup> LookupSpan<'lookup>,
    N: FormatFields<'writer> + 'static,

impl<'writer> FormatFields<'writer> for Pretty

impl<'writer, M> FormatFields<'writer> for Mwhere
    M: MakeOutput<&'writer mut dyn Write, Result>,
    M::Visitor: VisitFmt + VisitOutput<Result>,