Trait tracing_subscriber::fmt::format::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<'cx, 'writer, S, N> FormatFields<'writer> for FmtContext<'cx, S, N> where
    S: Subscriber + for<'lookup> LookupSpan<'lookup>,
    N: FormatFields<'writer> + 'static, 

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