diff options
| -rw-r--r-- | exercises/error_handling/errors5.rs | 4 | ||||
| -rw-r--r-- | exercises/error_handling/errors6.rs | 33 | ||||
| -rw-r--r-- | info.toml | 21 |
3 files changed, 35 insertions, 23 deletions
diff --git a/exercises/error_handling/errors5.rs b/exercises/error_handling/errors5.rs index 1b11800..365a869 100644 --- a/exercises/error_handling/errors5.rs +++ b/exercises/error_handling/errors5.rs @@ -43,8 +43,8 @@ impl PositiveNonzeroInteger { impl fmt::Display for CreationError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { let description = match *self { - CreationError::Negative => "Number is negative", - CreationError::Zero => "Number is zero", + CreationError::Negative => "number is negative", + CreationError::Zero => "number is zero", }; f.write_str(description) } diff --git a/exercises/error_handling/errors6.rs b/exercises/error_handling/errors6.rs index cee7250..0f6b27a 100644 --- a/exercises/error_handling/errors6.rs +++ b/exercises/error_handling/errors6.rs @@ -10,11 +10,20 @@ // I AM NOT DONE +use std::num::ParseIntError; + // This is a custom error type that we will be using in `parse_pos_nonzero()`. #[derive(PartialEq, Debug)] enum ParsePosNonzeroError { - CreationError, - ParseIntError + Creation(CreationError), + ParseInt(ParseIntError) +} + +impl ParsePosNonzeroError { + fn from_creation(err: CreationError) -> ParsePosNonzeroError { + ParsePosNonzeroError::Creation(err) + } + // TODO: add another error conversion function here. } fn parse_pos_nonzero(s: &str) @@ -24,7 +33,7 @@ fn parse_pos_nonzero(s: &str) // when `parse()` returns an error. let x: i64 = s.parse().unwrap(); PositiveNonzeroInteger::new(x) - .or(Err(ParsePosNonzeroError::CreationError)) + .map_err(ParsePosNonzeroError::from_creation) } // Don't change anything below this line. @@ -54,17 +63,18 @@ mod test { #[test] fn test_parse_error() { - assert_eq!( + // We can't construct a ParseIntError, so we have to pattern match. + assert!(matches!( parse_pos_nonzero("not a number"), - Err(ParsePosNonzeroError::ParseIntError) - ); + Err(ParsePosNonzeroError::ParseInt(_)) + )); } #[test] fn test_negative() { assert_eq!( parse_pos_nonzero("-555"), - Err(ParsePosNonzeroError::CreationError) + Err(ParsePosNonzeroError::Creation(CreationError::Negative)) ); } @@ -72,15 +82,14 @@ mod test { fn test_zero() { assert_eq!( parse_pos_nonzero("0"), - Err(ParsePosNonzeroError::CreationError) + Err(ParsePosNonzeroError::Creation(CreationError::Zero)) ); } #[test] fn test_positive() { - assert_eq!( - parse_pos_nonzero("42"), - Ok(PositiveNonzeroInteger(42)) - ); + let x = PositiveNonzeroInteger::new(42); + assert!(x.is_ok()); + assert_eq!(parse_pos_nonzero("42"), Ok(x.unwrap())); } } @@ -532,16 +532,19 @@ path = "exercises/error_handling/errors6.rs" mode = "test" hint = """ This exercise uses a completed version of `PositiveNonzeroInteger` from -the errors4. +errors4. -Below the TODO line, there is an example of using the `.or()` method -on a `Result` to transform one type of error into another. Try using -something similar on the `Result` from `parse()`. You might use the `?` -operator to return early from the function, or you might use a `match` -expression, or maybe there's another way! +Below the line that TODO asks you to change, there is an example of using +the `map_err()` method on a `Result` to transform one type of error into +another. Try using something similar on the `Result` from `parse()`. You +might use the `?` operator to return early from the function, or you might +use a `match` expression, or maybe there's another way! -Read more about `.or()` in the `std::result` documentation: -https://doc.rust-lang.org/std/result/enum.Result.html#method.or""" +You can create another function inside `impl ParsePosNonzeroError` to use +with `map_err()`. + +Read more about `map_err()` in the `std::result` documentation: +https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err""" # Generics @@ -927,7 +930,7 @@ hint = """ Follow the steps provided right before the `TryFrom` implementation. You can also use the example at https://doc.rust-lang.org/std/convert/trait.TryFrom.html -You might want to look back at the exercise errorsn (or its hints) to remind +You might want to look back at the exercise errors5 (or its hints) to remind yourself about how `Box<dyn Error>` works. If you're trying to return a string as an error, note that neither `str` |