[−][src]Trait snafu::OptionExt

pub trait OptionExt<T>: Sized {
    fn context<C>(self, context: C) -> Result<T, Context<NoneError, C>>;

    fn with_context<F, C>(self, context: F) -> Result<T, Context<NoneError, C>>
    where
        F: FnOnce() -> C;

    fn eager_context<C, E2>(self, context: C) -> Result<T, E2>
    where
        Context<NoneError, C>: Into<E2>,
    { ... }

    fn with_eager_context<F, C, E2>(self, context: F) -> Result<T, E2>
    where
        F: FnOnce() -> C,
        Context<NoneError, C>: Into<E2>,
    { ... }
}

Additions to Option.

Required methods

fn context<C>(self, context: C) -> Result<T, Context<NoneError, C>>

Convert an Option into a Result with additional context-sensitive information.

use snafu::{Snafu, OptionExt};

#[derive(Debug, Snafu)]
enum Error {
    UserLookup { user_id: i32 },
}

fn example(user_id: i32) -> Result<(), Error> {
    let name = username(user_id).context(UserLookup { user_id })?;
    println!("Username was {}", name);
    Ok(())
}

fn username(user_id: i32) -> Option<String> {
    /* ... */
}

Note that the From implementation generated by the macro will call Into::into on each field, so the types are not required to exactly match.

fn with_context<F, C>(self, context: F) -> Result<T, Context<NoneError, C>> where
    F: FnOnce() -> C, 

Convert an Option into a Result with lazily-generated context-sensitive information.

use snafu::{Snafu, OptionExt};

#[derive(Debug, Snafu)]
enum Error {
    UserLookup { user_id: i32, previous_ids: Vec<i32> },
}

fn example(user_id: i32) -> Result<(), Error> {
    let name = username(user_id).with_context(|| UserLookup {
        user_id,
        previous_ids: Vec::new(),
    })?;
    println!("Username was {}", name);
    Ok(())
}

fn username(user_id: i32) -> Option<String> {
    /* ... */
}

Note that this may not be needed in many cases because the From implementation generated by the macro will call Into::into on each field.

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Provided methods

fn eager_context<C, E2>(self, context: C) -> Result<T, E2> where
    Context<NoneError, C>: Into<E2>, 

Convert an Option into a Result with additional context-sensitive information.

This is most useful when the final Result type is already constrained.

use snafu::{Snafu, OptionExt};

#[derive(Debug, Snafu)]
enum Error {
    UserLookup { user_id: i32 },
}

fn example(user_id: i32) -> Result<String, Error> {
    username(user_id).eager_context(UserLookup { user_id })
}

fn username(user_id: i32) -> Option<String> {
    /* ... */
}

Note that the From implementation generated by the macro will call Into::into on each field, so the types are not required to exactly match.

fn with_eager_context<F, C, E2>(self, context: F) -> Result<T, E2> where
    F: FnOnce() -> C,
    Context<NoneError, C>: Into<E2>, 

Convert an Option into a Result with lazily-generated context-sensitive information.

This is most useful when the final Result type is already constrained.

use snafu::{Snafu, OptionExt};

#[derive(Debug, Snafu)]
enum Error {
    UserLookup { user_id: i32, previous_ids: Vec<i32> },
}

fn example(user_id: i32) -> Result<String, Error> {
    username(user_id).with_eager_context(|| UserLookup {
        user_id,
        previous_ids: Vec::new(),
    })
}

fn username(user_id: i32) -> Option<String> {
    /* ... */
}

Note that this may not be needed in many cases because the From implementation generated by the macro will call Into::into on each field.

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Implementations on Foreign Types

impl<T> OptionExt<T> for Option<T>[src]

fn eager_context<C, E2>(self, context: C) -> Result<T, E2> where
    Context<NoneError, C>: Into<E2>, [src]

fn with_eager_context<F, C, E2>(self, context: F) -> Result<T, E2> where
    F: FnOnce() -> C,
    Context<NoneError, C>: Into<E2>, [src]

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Implementors

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