Struct error_stack::provider::Demand

#[repr(transparent)]
pub struct Demand<'a>(_);

Available on nightly only.

A helper object for providing data by type.

A data provider provides values by calling this type’s provide methods.

Implementations

impl<'a> Demand<'a>

pub fn provide_value<T, F>(&mut self, fulfil: F) -> &mut Self where
    T: 'static,
    F: FnOnce() -> T, 

Provide a value or other type with only static lifetimes.

Examples

Provides a String by cloning.

use error_stack::provider::{Demand, Provider};

impl Provider for SomeConcreteType {
    fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
        demand.provide_value::<String, _>(|| self.field.clone());
    }
}

pub fn provide_ref<T: ?Sized + 'static>(&mut self, value: &'a T) -> &mut Self

Provide a reference, note that the referee type must be bounded by 'static, but may be unsized.

Examples

Provides a reference to a field as a &str.

use error_stack::provider::{Demand, Provider};

impl Provider for SomeConcreteType {
    fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
        demand.provide_ref::<str>(&self.field);
    }
}