tracing_subscriber::fmt::writer

Struct BoxMakeWriter

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pub struct BoxMakeWriter { /* private fields */ }
Available on crate features fmt and std only.
Expand description

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§

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impl BoxMakeWriter

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pub fn new<M>(make_writer: M) -> Self
where M: for<'a> MakeWriter<'a> + Send + Sync + 'static,

Constructs a BoxMakeWriter wrapping a type implementing MakeWriter.

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impl Debug for BoxMakeWriter

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

Formats the value using the given formatter. Read more
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impl<'a> MakeWriter<'a> for BoxMakeWriter

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type Writer = Box<dyn Write + 'a>

The concrete io::Write implementation returned by make_writer.
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fn make_writer(&'a self) -> Self::Writer

Returns an instance of Writer. Read more
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fn make_writer_for(&'a self, meta: &Metadata<'_>) -> Self::Writer

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

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<'a, M> MakeWriterExt<'a> for M
where M: MakeWriter<'a>,

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fn with_max_level(self, level: Level) -> WithMaxLevel<Self>
where Self: Sized,

Available on crate features fmt and std only.
Wraps self and returns a MakeWriter that will only write output for events at or below the provided verbosity Level. For instance, Level::TRACE is considered to be _more verbosethanLevel::INFO`. Read more
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fn with_min_level(self, level: Level) -> WithMinLevel<Self>
where Self: Sized,

Available on crate features fmt and std only.
Wraps self and returns a MakeWriter that will only write output for events at or above the provided verbosity Level. Read more
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fn with_filter<F>(self, filter: F) -> WithFilter<Self, F>
where Self: Sized, F: Fn(&Metadata<'_>) -> bool,

Available on crate features fmt and std only.
Wraps self with a predicate that takes a span or event’s Metadata and returns a bool. The returned MakeWriter’s MakeWriter::make_writer_for method will check the predicate to determine if a writer should be produced for a given span or event. Read more
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fn and<B>(self, other: B) -> Tee<Self, B>
where Self: Sized, B: MakeWriter<'a> + Sized,

Available on crate features fmt and std only.
Combines self with another type implementing MakeWriter, returning a new MakeWriter that produces writers that write to both outputs. Read more
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fn or_else<W, B>(self, other: B) -> OrElse<Self, B>
where Self: MakeWriter<'a, Writer = OptionalWriter<W>> + Sized, B: MakeWriter<'a> + Sized, W: Write,

Available on crate features fmt and std only.
Combines self with another type implementing MakeWriter, returning a new MakeWriter that calls other’s make_writer if self’s make_writer returns OptionalWriter::none. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 32 bytes