Struct const_format::fmt::DebugStruct

pub struct DebugStruct<'f, 'w> { /* private fields */ }

Available on crate feature fmt only.

A helper struct for debug formatting a braced struct, or braced variant.

Example

This example demonstrates how you can debug format a struct, and a braced variant.

#![feature(const_mut_refs)]

use const_format::{Error, Formatter};
use const_format::{call_debug_fmt, coerce_to_fmt, formatc, impl_fmt, try_};

fn main() {
    const STRUC: &str = formatc!("{:?}", Foo { a: 5, b: [8, 13, 21], c: "34" });
    const ENUM_: &str = formatc!("{:?}", Bar::Baz { d: false, e: None });
     
    assert_eq!(STRUC, "Foo { a: 5, b: [8, 13, 21], c: \"34\" }");
    assert_eq!(ENUM_, "Baz { d: false, e: None }");
}

struct Foo{
    a: u32,
    b: [u32; 3],
    c: &'static str,
}

enum Bar {
    Baz{
        d: bool,
        e: Option<bool>,
    }
}

impl_fmt!{
    impl Foo;
     
    const fn const_debug_fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
        let mut f = f.debug_struct("Foo");
        try_!(coerce_to_fmt!(&self.a).const_debug_fmt(f.field("a")));
        try_!(coerce_to_fmt!(&self.b).const_debug_fmt(f.field("b")));
        try_!(coerce_to_fmt!(&self.c).const_debug_fmt(f.field("c")));
        f.finish()
    }
}

impl_fmt!{
    impl Bar;
     
    const fn const_debug_fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
        match self {
            Bar::Baz{d, e} => {
                let mut f = f.debug_struct("Baz");
                 
                // This macro allows debug formatting some generic types that
                // don't have a const_debug_fmt fn, like Options which wrap non-std types.
                call_debug_fmt!(std, d, f.field("d"));
                call_debug_fmt!(Option, e, f.field("e"));
                 
                f.finish()
            }
        }
    }
}

Implementations

impl<'f, 'w> DebugStruct<'f, 'w>

pub const fn field(&mut self, name: &str) -> &mut Formatter<'w>

Adds a field to the formatted output.

pub const fn finish(self) -> Result<(), Error>

Finishes writing the struct/variant, and if anything went wrong in the field method,returns an error.