Trait core::fmt::Write

pub trait Write {
    fn write_str(&mut self, s: &str) -> Result;

    fn write_char(&mut self, c: char) -> Result { ... }
    fn write_fmt(&mut self, args: Arguments) -> Result { ... }
}

A collection of methods that are required to format a message into a stream.

This trait is the type which this modules requires when formatting information. This is similar to the standard library's io::Write trait, but it is only intended for use in libcore.

This trait should generally not be implemented by consumers of the standard library. The write! macro accepts an instance of io::Write, and the io::Write trait is favored over implementing this trait.

Required Methods

fn write_str(&mut self, s: &str) -> Result

Writes a slice of bytes into this writer, returning whether the write succeeded.

This method can only succeed if the entire byte slice was successfully written, and this method will not return until all data has been written or an error occurs.

Errors

This function will return an instance of Error on error.

Examples

use std::fmt::{Error, Write};

fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
    f.write_str(s)
}

let mut buf = String::new();
writer(&mut buf, "hola").unwrap();
assert_eq!(&buf, "hola");

Provided Methods

fn write_char(&mut self, c: char) -> Result

Writes a char into this writer, returning whether the write succeeded.

A single char may be encoded as more than one byte. This method can only succeed if the entire byte sequence was successfully written, and this method will not return until all data has been written or an error occurs.

Errors

This function will return an instance of Error on error.

Examples

use std::fmt::{Error, Write};

fn writer<W: Write>(f: &mut W, c: char) -> Result<(), Error> {
    f.write_char(c)
}

let mut buf = String::new();
writer(&mut buf, 'a').unwrap();
writer(&mut buf, 'b').unwrap();
assert_eq!(&buf, "ab");

fn write_fmt(&mut self, args: Arguments) -> Result

Glue for usage of the write! macro with implementors of this trait.

This method should generally not be invoked manually, but rather through the write! macro itself.

Examples

use std::fmt::{Error, Write};

fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
    f.write_fmt(format_args!("{}", s))
}

let mut buf = String::new();
writer(&mut buf, "world").unwrap();
assert_eq!(&buf, "world");

Implementors

• impl<'a, W: Write + ?Sized> Write for &'a mut W

• impl<'a> Write for Formatter<'a>