Trait writeable::Writeable

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pub trait Writeable {
    // Provided methods
    fn write_to<W: Write + ?Sized>(&self, sink: &mut W) -> Result { ... }
    fn write_to_parts<S: PartsWrite + ?Sized>(&self, sink: &mut S) -> Result { ... }
    fn writeable_length_hint(&self) -> LengthHint { ... }
    fn write_to_string(&self) -> Cow<'_, str> { ... }
}
Expand description

Writeable is an alternative to std::fmt::Display with the addition of a length function.

Provided Methods§

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fn write_to<W: Write + ?Sized>(&self, sink: &mut W) -> Result

Writes a string to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to_parts, and discards any Part annotations.

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fn write_to_parts<S: PartsWrite + ?Sized>(&self, sink: &mut S) -> Result

Write bytes and Part annotations to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to, and doesn’t produce any Part annotations.

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fn writeable_length_hint(&self) -> LengthHint

Returns a hint for the number of UTF-8 bytes that will be written to the sink.

Override this method if it can be computed quickly.

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fn write_to_string(&self) -> Cow<'_, str>

Creates a new String with the data from this Writeable. Like ToString, but smaller and faster.

The default impl allocates an owned String. However, if it is possible to return a borrowed string, overwrite this method to return a Cow::Borrowed.

To remove the Cow wrapper, call .into_owned() or .as_str() as appropriate.

§Examples

Inspect a Writeable before writing it to the sink:

use core::fmt::{Result, Write};
use writeable::Writeable;

fn write_if_ascii<W, S>(w: &W, sink: &mut S) -> Result
where
    W: Writeable + ?Sized,
    S: Write + ?Sized,
{
    let s = w.write_to_string();
    if s.is_ascii() {
        sink.write_str(&s)
    } else {
        Ok(())
    }
}

Convert the Writeable into a fully owned String:

use writeable::Writeable;

fn make_string(w: &impl Writeable) -> String {
    w.write_to_string().into_owned()
}

Object Safety§

This trait is not object safe.

Implementations on Foreign Types§

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impl Writeable for char

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impl Writeable for i8

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impl Writeable for i16

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impl Writeable for i32

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impl Writeable for i64

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impl Writeable for i128

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impl Writeable for isize

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impl Writeable for str

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fn write_to_string(&self) -> Cow<'_, str>

Returns a borrowed str.

§Examples
use std::borrow::Cow;
use writeable::Writeable;

let cow = "foo".write_to_string();
assert!(matches!(cow, Cow::Borrowed(_)));
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fn write_to<W: Write + ?Sized>(&self, sink: &mut W) -> Result

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fn writeable_length_hint(&self) -> LengthHint

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impl Writeable for u8

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impl Writeable for u16

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impl Writeable for u32

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impl Writeable for u64

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impl Writeable for u128

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impl Writeable for usize

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impl Writeable for String

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impl<'a, T: ?Sized + Writeable + ToOwned> Writeable for Cow<'a, T>

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impl<'a, T: ?Sized + Writeable> Writeable for Box<T>

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impl<'a, T: ?Sized + Writeable> Writeable for Rc<T>

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impl<'a, T: ?Sized + Writeable> Writeable for Arc<T>

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impl<T: Writeable + ?Sized> Writeable for &T

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impl<W0, W1> Writeable for Either<W0, W1>
where W0: Writeable, W1: Writeable,

A Writeable impl that delegates to one type or another type.

Implementors§