Struct BoxMakeWriter

pub struct BoxMakeWriter { /* private fields */ }

A writer that erases the specific io::Write and MakeWriter types being used.

This is useful in cases where the concrete type of the writer cannot be known until runtime.

Examples

A function that returns a Subscriber that will write to either stdout or stderr:

fn dynamic_writer(use_stderr: bool) -> impl Subscriber {
    let writer = if use_stderr {
        BoxMakeWriter::new(std::io::stderr)
    } else {
        BoxMakeWriter::new(std::io::stdout)
    };

    tracing_subscriber::fmt().with_writer(writer).finish()
}

Implementations

impl BoxMakeWriter

pub fn new<M>(make_writer: M) -> BoxMakeWriter

where M: for<'a> MakeWriter<'a> + Send + Sync + 'static,

Constructs a BoxMakeWriter wrapping a type implementing MakeWriter.

Trait Implementations

impl Debug for BoxMakeWriter

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a> MakeWriter<'a> for BoxMakeWriter

type Writer = Box<dyn Write + 'a>

The concrete io::Write implementation returned by make_writer.

fn make_writer(&'a self) -> <BoxMakeWriter as MakeWriter<'a>>::Writer

Returns an instance of Writer.

fn make_writer_for( &'a self, meta: &Metadata<'_>, ) -> <BoxMakeWriter as MakeWriter<'a>>::Writer

Returns a Writer for writing data from the span or event described by the provided Metadata.