Struct Rule 

pub struct Rule(/* private fields */);

One field’s validation rule: returns Some(message) if the value is invalid, None if it passes.

Implementations

impl Rule

pub fn new(check: impl Fn(&str) -> Option<String> + 'static) -> Self

An arbitrary rule from a closure.

pub fn check(&self, value: &str) -> Option<String>

Applies the rule to value.

pub fn required(message: impl Into<String>) -> Self

Non-empty (leading and trailing whitespace ignored).

pub fn min_len(n: usize, message: impl Into<String>) -> Self

At least n characters (counted as chars, whitespace included).

pub fn max_len(n: usize, message: impl Into<String>) -> Self

At most n characters.

pub fn email(message: impl Into<String>) -> Self

A plausible e-mail shape: local@domain, a non-empty local part, and a domain containing a dot that is not flush against the edges (a heuristic, not the RFC).

pub fn all(rules: impl IntoIterator<Item = Rule>) -> Self

Combines rules: the first to fail, in order, wins.