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Finished errors, finally!

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This commit is contained in:
Justin Kelz 2022-04-04 09:59:14 -07:00
parent 2ad8b9b469
commit c11a76cdf7
1 changed files with 21 additions and 5 deletions
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26
exercises/error_handling/errors6.rs
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@ -8,7 +8,6 @@
// Make these tests pass! Execute `rustlings hint errors6` for hints :)
// I AM NOT DONE
use std::num::ParseIntError;
@ -16,7 +15,7 @@ use std::num::ParseIntError;
#[derive(PartialEq, Debug)]
enum ParsePosNonzeroError {
Creation(CreationError),
ParseInt(ParseIntError)
ParseInt(ParseIntError),
}
impl ParsePosNonzeroError {
@ -24,6 +23,9 @@ impl ParsePosNonzeroError {
ParsePosNonzeroError::Creation(err)
}
// TODO: add another error conversion function here.
fn from_parse(err: ParseIntError) -> ParsePosNonzeroError {
ParsePosNonzeroError::ParseInt(err)
}
}
fn parse_pos_nonzero(s: &str)
@ -31,9 +33,23 @@ fn parse_pos_nonzero(s: &str)
{
// TODO: change this to return an appropriate error instead of panicking
// when `parse()` returns an error.
let x: i64 = s.parse().unwrap();
PositiveNonzeroInteger::new(x)
.map_err(ParsePosNonzeroError::from_creation)
/*
We're greeted with
############################
---- test::test_parse_error stdout ----
thread 'test::test_parse_error' panicked at 'called `Result::unwrap()`
on an `Err` value: ParseIntError { kind: InvalidDigit }',
exercises/error_handling/errors6.rs:34:28
############################
So this is really applying a function mapping one error to another
Applying map_err to something that is Ok doesn't affect the outcome
pub fn map_err<F, O>(self, op: O) -> Result<T, F>
where
O: FnOnce(E) -> F,
*/
let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parse)?; //Originally this was .unwrap() which causes a panic!;
PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
}
// Don't change anything below this line.