Crate rt_format[−][src]

Expand description

Fully-runtime equivalent of the format! macro.

Allows formatting strings like the format! macro, with the formatting string and the arguments provided at runtime. This crate supports all the formatting features of the format! macro, except for the fill character.

Examples

use rt_format::{Arguments, Format, FormattableValue, Specifier};
use std::cmp::PartialEq;
use std::convert::TryInto;
use std::fmt;

#[derive(Debug, PartialEq)]
pub enum Variant {
    Int(i32),
    Float(f64),
}
 
impl FormattableValue for Variant {
    fn supports_format(&self, spec: &Specifier) -> bool {
        match self {
            Self::Int(_) => true,
            Self::Float(_) => match spec.format {
                Format::Display | Format::Debug | Format::LowerExp | Format::UpperExp => true,
                _ => false,
            },
        }
    }
 
    fn fmt_display(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::Display::fmt(&val, f),
            Self::Float(val) => fmt::Display::fmt(&val, f),
        }
    }
 
    fn fmt_debug(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self, f)
    }
 
    fn fmt_octal(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::Octal::fmt(&val, f),
            _ => Err(fmt::Error),
        }
    }
 
    fn fmt_lower_hex(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::LowerHex::fmt(&val, f),
            _ => Err(fmt::Error),
        }
    }
 
    fn fmt_upper_hex(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::UpperHex::fmt(&val, f),
            _ => Err(fmt::Error),
        }
    }
 
    fn fmt_binary(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::Binary::fmt(&val, f),
            _ => Err(fmt::Error),
        }
    }
 
    fn fmt_lower_exp(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::LowerExp::fmt(&val, f),
            Self::Float(val) => fmt::LowerExp::fmt(&val, f),
        }
    }
 
    fn fmt_upper_exp(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Int(val) => fmt::UpperExp::fmt(&val, f),
            Self::Float(val) => fmt::UpperExp::fmt(&val, f),
        }
    }
}
 
impl TryInto<usize> for &Variant {
    type Error = ();
    fn try_into(self) -> Result<usize, Self::Error> {
        match self {
            Variant::Int(val) => (*val).try_into().map_err(|_| ()),
            Variant::Float(_) => Err(()),
        }
    }
}
 
fn main() {
    use std::collections::HashMap;
 
    let pos_args = [Variant::Int(42), Variant::Int(5)];
 
    let mut named_args = HashMap::new();
    named_args.insert("foo".to_string(), Variant::Float(42.042));
 
    let args = Arguments::parse("{:#x} [{0:<5}] {foo:.1$}", &pos_args, &named_args).unwrap();
    assert_eq!("0x2a [42   ] 42.04200", format!("{}", args));
}