Struct ContextField 

pub struct ContextField { /* private fields */ }

One piece of context added with the ErrorExt or ErrorContext methods.

Read them with CauseExt::context_fields or CauseExt::context_value.

use rama_error::{BoxError, BoxErrorExt, CauseExt, ErrorExt};

#[derive(Debug, PartialEq)]
struct Port(u16);

let error = BoxError::from_static_str("connect failed")
    .context_field("attempt", 2u8)
    .context_debug_field("port", Port(443))
    .context_hex_field("flags", 0x1fu8)
    .context("giving up");

let fields: Vec<_> = error
    .context_fields()
    .map(|field| (field.key(), field.value().to_string()))
    .collect();
assert_eq!(
    fields,
    [
        (Some("attempt"), "2".to_owned()),
        (Some("port"), "Port(443)".to_owned()),
        (Some("flags"), "1f".to_owned()),
        (None, "giving up".to_owned()),
    ]
);

// Debug and hex fields keep the type they were added with.
assert_eq!(error.context_value::<Port>("port"), Some(&Port(443)));
assert_eq!(error.context_value::<u8>("flags"), Some(&0x1f));
assert_eq!(error.context_value::<u8>("attempt"), Some(&2));
assert_eq!(error.context_value::<u16>("attempt"), None);

Implementations

impl ContextField

pub fn key(&self) -> Option<&'static str>

The key, None for a value added without one.

pub fn value(&self) -> &dyn Display

The value as it is displayed, before quoting and escaping.

pub fn downcast_ref<T>(&self) -> Option<&T>

where T: Any,

The value as the type it was added with.

Values added with the _debug and _hex methods are found as their original type, _str values as String.

Trait Implementations

impl Debug for ContextField

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

Formats the value using the given formatter.

impl Display for ContextField

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

Formats the value using the given formatter.