errors6 solution

This commit is contained in:
mo8it 2024-06-27 01:12:50 +02:00
parent 129884aff7
commit b1daea1fe8
3 changed files with 138 additions and 52 deletions

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@ -1,52 +1,51 @@
// Using catch-all error types like `Box<dyn error::Error>` 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<dyn Error>` 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<PositiveNonzeroInteger, ParsePosNonzeroError> {
// 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<PositiveNonzeroInteger, CreationError> {
fn new(value: i64) -> Result<Self, CreationError> {
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<Self, ParsePosNonzeroError> {
// 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));
}
}

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@ -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"""

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@ -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<dyn Error>` 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<Self, CreationError> {
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<Self, ParsePosNonzeroError> {
// 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));
}
}