Trait Invariant

pub trait Invariant: Sized {
    type Error: Display;

    // Required method
    fn check(slice: &str) -> Result<(), Self::Error>;
}

Invariant for a Ck or Check.

The Ck and Check types are checked strings types that make guarantees about the contents of the string. These guarantees are determined by this trait, Invariant which distinguishes whether or not a string upholds some arbitrary invariants via the Invariant::check function. If the Err is returned, then the invariant is broken, and the Ck or Check generic over the invariant cannot be constructed.

Examples

Declaring an invariant that the string contains no whitespace:

struct NoWhitespace;

impl Invariant for NoWhitespace {
    type Error = char;

    fn check(slice: &str) -> Result<(), Self::Error> {
        match slice.chars().find(|ch| ch.is_whitespace()) {
            Some(ch) => Err(ch),
            None => Ok(()),
        }
    }
}

Required Associated Types

type Error: Display

The type returned in the event that an invariant is broken.

When formatting, Error should not be capitalized and should not end with a period.

Required Methods

fn check(slice: &str) -> Result<(), Self::Error>

Returns Ok if the string upholds the invariant, otherwise Err.

This function is used internally in Check::from_buf and Ck::from_slice.

Object Safety

This trait is not object safe.

Implementors