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pub fn find_by_id_or<Id: PartialEq, Val: Copy>(
arr: &[(Id, Option<Val>)],
id: Id,
default: Val,
) -> Val {
arr.iter()
.find(|(elem_id, _)| *elem_id == id)
.map_or(default, |row| match row {
(_, Some(quantity)) => *quantity,
(_, _) => default,
})
}
#[cfg(test)]
mod test {
use super::find_by_id_or;
#[test]
fn when_no_elements_then_return_default() {
let arr = [];
let result = find_by_id_or(&arr, 1, 42);
assert_eq!(result, 42);
}
#[test]
fn when_id_not_in_elements_then_return_default() {
let arr = [(0, Some(100)), (2, Some(200))];
let result = find_by_id_or(&arr, 1, 42);
assert_eq!(result, 42);
}
#[test]
fn when_value_is_none_then_return_default() {
let arr = [(1, None)];
let result = find_by_id_or(&arr, 1, 42);
assert_eq!(result, 42);
}
#[test]
fn when_value_is_some_then_return_value() {
let arr = [(1, Some(67))];
let result = find_by_id_or(&arr, 1, 42);
assert_eq!(result, 67);
}
}
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