diff --git a/exercises/13_error_handling/errors6.rs b/exercises/13_error_handling/errors6.rs index 8b08e086..0652abda 100644 --- a/exercises/13_error_handling/errors6.rs +++ b/exercises/13_error_handling/errors6.rs @@ -1,52 +1,51 @@ -// Using catch-all error types like `Box` isn't recommended -// for library code, where callers might want to make decisions based on the -// error content, instead of printing it out or propagating it further. Here, we -// define a custom error type to make it possible for callers to decide what to -// do next when our function returns an error. +// Using catch-all error types like `Box` isn't recommended for +// library code where callers might want to make decisions based on the error +// content instead of printing it out or propagating it further. Here, we define +// a custom error type to make it possible for callers to decide what to do next +// when our function returns an error. use std::num::ParseIntError; -// This is a custom error type that we will be using in `parse_pos_nonzero()`. -#[derive(PartialEq, Debug)] -enum ParsePosNonzeroError { - Creation(CreationError), - ParseInt(ParseIntError), -} - -impl ParsePosNonzeroError { - fn from_creation(err: CreationError) -> ParsePosNonzeroError { - ParsePosNonzeroError::Creation(err) - } - // TODO: add another error conversion function here. - // fn from_parseint... -} - -fn parse_pos_nonzero(s: &str) -> Result { - // 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) -} - -// Don't change anything below this line. - -#[derive(PartialEq, Debug)] -struct PositiveNonzeroInteger(u64); - #[derive(PartialEq, Debug)] enum CreationError { Negative, Zero, } +// A custom error type that we will be using in `PositiveNonzeroInteger::parse`. +#[derive(PartialEq, Debug)] +enum ParsePosNonzeroError { + Creation(CreationError), + ParseInt(ParseIntError), +} + +impl ParsePosNonzeroError { + fn from_creation(err: CreationError) -> Self { + Self::Creation(err) + } + + // TODO: Add another error conversion function here. + // fn from_parseint(???) -> Self { ??? } +} + +#[derive(PartialEq, Debug)] +struct PositiveNonzeroInteger(u64); + impl PositiveNonzeroInteger { - fn new(value: i64) -> Result { + fn new(value: i64) -> Result { match value { x if x < 0 => Err(CreationError::Negative), x if x == 0 => Err(CreationError::Zero), - x => Ok(PositiveNonzeroInteger(x as u64)), + x => Ok(Self(x as u64)), } } + + fn parse(s: &str) -> Result { + // TODO: change this to return an appropriate error instead of panicking + // when `parse()` returns an error. + let x: i64 = s.parse().unwrap(); + Self::new(x).map_err(ParsePosNonzeroError::from_creation) + } } fn main() { @@ -56,36 +55,36 @@ fn main() { #[cfg(test)] mod test { use super::*; + use std::num::IntErrorKind; #[test] fn test_parse_error() { - // We can't construct a ParseIntError, so we have to pattern match. assert!(matches!( - parse_pos_nonzero("not a number"), - Err(ParsePosNonzeroError::ParseInt(_)) + PositiveNonzeroInteger::parse("not a number"), + Err(ParsePosNonzeroError::ParseInt(_)), )); } #[test] fn test_negative() { assert_eq!( - parse_pos_nonzero("-555"), - Err(ParsePosNonzeroError::Creation(CreationError::Negative)) + PositiveNonzeroInteger::parse("-555"), + Err(ParsePosNonzeroError::Creation(CreationError::Negative)), ); } #[test] fn test_zero() { assert_eq!( - parse_pos_nonzero("0"), - Err(ParsePosNonzeroError::Creation(CreationError::Zero)) + PositiveNonzeroInteger::parse("0"), + Err(ParsePosNonzeroError::Creation(CreationError::Zero)), ); } #[test] fn test_positive() { - let x = PositiveNonzeroInteger::new(42); - assert!(x.is_ok()); - assert_eq!(parse_pos_nonzero("42"), Ok(x.unwrap())); + let x = PositiveNonzeroInteger::new(42).unwrap(); + assert_eq!(x.0, 42); + assert_eq!(PositiveNonzeroInteger::parse("42"), Ok(x)); } } diff --git a/rustlings-macros/info.toml b/rustlings-macros/info.toml index 700c1792..dc288c0c 100644 --- a/rustlings-macros/info.toml +++ b/rustlings-macros/info.toml @@ -714,17 +714,13 @@ https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/reen name = "errors6" dir = "13_error_handling" hint = """ -This exercise uses a completed version of `PositiveNonzeroInteger` from -errors4. +This exercise uses a completed version of `PositiveNonzeroInteger` from the +previous exercises. 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! - -You can create another function inside `impl ParsePosNonzeroError` to use -with `map_err()`. +can then use the `?` operator to return early. Read more about `map_err()` in the `std::result` documentation: https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err""" diff --git a/solutions/13_error_handling/errors6.rs b/solutions/13_error_handling/errors6.rs index 4e181989..70680cf0 100644 --- a/solutions/13_error_handling/errors6.rs +++ b/solutions/13_error_handling/errors6.rs @@ -1 +1,92 @@ -// Solutions will be available before the stable release. Thank you for testing the beta version 🥰 +// Using catch-all error types like `Box` isn't recommended for +// library code where callers might want to make decisions based on the error +// content instead of printing it out or propagating it further. Here, we define +// a custom error type to make it possible for callers to decide what to do next +// when our function returns an error. + +use std::num::ParseIntError; + +#[derive(PartialEq, Debug)] +enum CreationError { + Negative, + Zero, +} + +// A custom error type that we will be using in `PositiveNonzeroInteger::parse`. +#[derive(PartialEq, Debug)] +enum ParsePosNonzeroError { + Creation(CreationError), + ParseInt(ParseIntError), +} + +impl ParsePosNonzeroError { + fn from_creation(err: CreationError) -> Self { + Self::Creation(err) + } + + fn from_parseint(err: ParseIntError) -> Self { + Self::ParseInt(err) + } +} + +#[derive(PartialEq, Debug)] +struct PositiveNonzeroInteger(u64); + +impl PositiveNonzeroInteger { + fn new(value: i64) -> Result { + match value { + x if x < 0 => Err(CreationError::Negative), + x if x == 0 => Err(CreationError::Zero), + x => Ok(Self(x as u64)), + } + } + + fn parse(s: &str) -> Result { + // Return an appropriate error instead of panicking when `parse()` + // returns an error. + let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?; + // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + Self::new(x).map_err(ParsePosNonzeroError::from_creation) + } +} + +fn main() { + // You can optionally experiment here. +} + +#[cfg(test)] +mod test { + use super::*; + use std::num::IntErrorKind; + + #[test] + fn test_parse_error() { + assert!(matches!( + PositiveNonzeroInteger::parse("not a number"), + Err(ParsePosNonzeroError::ParseInt(_)), + )); + } + + #[test] + fn test_negative() { + assert_eq!( + PositiveNonzeroInteger::parse("-555"), + Err(ParsePosNonzeroError::Creation(CreationError::Negative)), + ); + } + + #[test] + fn test_zero() { + assert_eq!( + PositiveNonzeroInteger::parse("0"), + Err(ParsePosNonzeroError::Creation(CreationError::Zero)), + ); + } + + #[test] + fn test_positive() { + let x = PositiveNonzeroInteger::new(42).unwrap(); + assert_eq!(x.0, 42); + assert_eq!(PositiveNonzeroInteger::parse("42"), Ok(x)); + } +}