[−][src]Trait yewtil::NeqAssignBy

pub trait NeqAssignBy<NEW> {
    fn neq_assign_by<F>(&mut self, new: NEW, eq: F) -> ShouldRender
    where
        F: FnOnce(&NEW, &NEW) -> bool;
}

Blanket trait to provide a convenience method for assigning props in changed or updating values in update.

Like neq_assign, but for cases where self doesn't impl PartialEq or a nonstandard equality comparison is needed.

Useful for Result<T, E: !PartialEq>.

Required methods

fn neq_assign_by<F>(&mut self, new: NEW, eq: F) -> ShouldRender where
    F: FnOnce(&NEW, &NEW) -> bool, 

#[derive(Clone, Debug)]
struct NonComparableError;

fn eq_by_ok<T, E>(a: &Result<T, E>, b: &Result<T, E>) -> bool
where
    T: PartialEq,
{
    match (a, b) {
        (Ok(_), Err(_))
        | (Err(_), Ok(_))
        | (Err(_), Err(_)) => false,
        (Ok(a), Ok(b)) => a == b,
    }
}

let mut foo: Result<u32, NonComparableError> = Ok(1);

// Won't compile
// assert_eq!(foo.neq_assign(Ok(42)), true)

assert_eq!(foo.neq_assign_by(Ok(42), eq_by_ok), true);
assert_eq!(foo.clone().unwrap(), 42);

assert_eq!(foo.neq_assign_by(Err(NonComparableError), eq_by_ok), true);
assert!(foo.is_err());

// The tradeoff: all assignments of an `Err` value will count as updates, even if they are
// "the same" for all practical intents and purposes.
assert_eq!(foo.neq_assign_by(Err(NonComparableError), eq_by_ok), true);
assert_eq!(foo.neq_assign_by(Err(NonComparableError), eq_by_ok), true);
assert_eq!(foo.neq_assign_by(Err(NonComparableError), eq_by_ok), true);
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Implementors

impl<T: BorrowMut<U>, U> NeqAssignBy<U> for T[src]

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