Trait custom_format::runtime::CustomFormat

pub trait CustomFormat {
    fn fmt(&self, f: &mut Formatter<'_>, spec: &str) -> Result;
}

Trait for custom formatting with runtime format checking

Required Methods

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

Formats the value using the given formatter.

Examples

use custom_format::runtime::{self as cfmt, CustomFormat};

use core::fmt;

#[derive(Debug)]
struct Hex(u8);

impl CustomFormat for Hex {
    fn fmt(&self, f: &mut fmt::Formatter, spec: &str) -> fmt::Result {
        match spec {
            "x" => write!(f, "{:#02x}", self.0),
            "X" => write!(f, "{:#02X}", self.0),
            _ => Err(fmt::Error),
        }
    }
}

assert_eq!(cfmt::format!("{0:X?}, {0 :x}, {0 :X}", Hex(0xAB)), "Hex(AB), 0xab, 0xAB");

The following statement panics at runtime since "z" is not a valid format specifier:

cfmt::println!("{ :z}", Hex(0));

Implementors