feat: add advanced_errs2
New exercise to demonstrate traits that make it easier for other code to consume our custom error types.
This commit is contained in:
parent
882d535ba8
commit
abd6b70c72
|
@ -0,0 +1,203 @@
|
||||||
|
// advanced_errs2.rs
|
||||||
|
|
||||||
|
// This exercise demonstrates a few traits that are useful for custom error
|
||||||
|
// types to implement, especially so that other code can consume the custom
|
||||||
|
// error type more usefully.
|
||||||
|
|
||||||
|
// Make this compile, and make the tests pass!
|
||||||
|
// Execute `rustlings hint advanced_errs2` for hints.
|
||||||
|
|
||||||
|
// Steps:
|
||||||
|
// 1. Implement a missing trait so that `main()` will compile.
|
||||||
|
// 2. Complete the partial implementation of `From` for
|
||||||
|
// `ParseClimateError`.
|
||||||
|
// 3. Handle the missing error cases in the `FromStr` implementation for
|
||||||
|
// `Climate`.
|
||||||
|
// 4. Complete the partial implementation of `Display` for
|
||||||
|
// `ParseClimateError`.
|
||||||
|
|
||||||
|
// I AM NOT DONE
|
||||||
|
|
||||||
|
use std::error::Error;
|
||||||
|
use std::fmt::{self, Display, Formatter};
|
||||||
|
use std::num::{ParseFloatError, ParseIntError};
|
||||||
|
use std::str::FromStr;
|
||||||
|
|
||||||
|
// This is the custom error type that we will be using for the parser for
|
||||||
|
// `Climate`.
|
||||||
|
#[derive(Debug, PartialEq)]
|
||||||
|
enum ParseClimateError {
|
||||||
|
Empty,
|
||||||
|
BadLen,
|
||||||
|
NoCity,
|
||||||
|
ParseInt(ParseIntError),
|
||||||
|
ParseFloat(ParseFloatError),
|
||||||
|
}
|
||||||
|
|
||||||
|
// This `From` implementation allows the `?` operator to work on
|
||||||
|
// `ParseIntError` values.
|
||||||
|
impl From<ParseIntError> for ParseClimateError {
|
||||||
|
fn from(e: ParseIntError) -> Self {
|
||||||
|
Self::ParseInt(e)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// This `From` implementation allows the `?` operator to work on
|
||||||
|
// `ParseFloatError` values.
|
||||||
|
impl From<ParseFloatError> for ParseClimateError {
|
||||||
|
fn from(e: ParseFloatError) -> Self {
|
||||||
|
// TODO: Complete this function
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// TODO: Implement a missing trait so that `main()` below will compile. It
|
||||||
|
// is not necessary to implement any methods inside the missing trait.
|
||||||
|
|
||||||
|
// The `Display` trait allows for other code to obtain the error formatted
|
||||||
|
// as a user-visible string.
|
||||||
|
impl Display for ParseClimateError {
|
||||||
|
// TODO: Complete this function so that it produces the correct strings
|
||||||
|
// for each error variant.
|
||||||
|
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
|
||||||
|
// Imports the variants to make the following code more compact.
|
||||||
|
use ParseClimateError::*;
|
||||||
|
match self {
|
||||||
|
NoCity => write!(f, "no city name"),
|
||||||
|
ParseFloat(e) => write!(f, "error parsing temperature: {}", e),
|
||||||
|
_ => write!(f, "unhandled error!"),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
#[derive(Debug, PartialEq)]
|
||||||
|
struct Climate {
|
||||||
|
city: String,
|
||||||
|
year: u32,
|
||||||
|
temp: f32,
|
||||||
|
}
|
||||||
|
|
||||||
|
// Parser for `Climate`.
|
||||||
|
// 1. Split the input string into 3 fields: city, year, temp.
|
||||||
|
// 2. Return an error if the string is empty or has the wrong number of
|
||||||
|
// fields.
|
||||||
|
// 3. Return an error if the city name is empty.
|
||||||
|
// 4. Parse the year as a `u32` and return an error if that fails.
|
||||||
|
// 5. Parse the temp as a `f32` and return an error if that fails.
|
||||||
|
// 6. Return an `Ok` value containing the completed `Climate` value.
|
||||||
|
impl FromStr for Climate {
|
||||||
|
type Err = ParseClimateError;
|
||||||
|
// TODO: Complete this function by making it handle the missing error
|
||||||
|
// cases.
|
||||||
|
fn from_str(s: &str) -> Result<Self, Self::Err> {
|
||||||
|
let v: Vec<_> = s.split(',').collect();
|
||||||
|
let (city, year, temp) = match &v[..] {
|
||||||
|
[city, year, temp] => (city.to_string(), year, temp),
|
||||||
|
_ => return Err(ParseClimateError::BadLen),
|
||||||
|
};
|
||||||
|
let year: u32 = year.parse()?;
|
||||||
|
let temp: f32 = temp.parse()?;
|
||||||
|
Ok(Climate { city, year, temp })
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Don't change anything below this line (other than to enable ignored
|
||||||
|
// tests).
|
||||||
|
|
||||||
|
fn main() -> Result<(), Box<dyn Error>> {
|
||||||
|
println!("{:?}", "Hong Kong,1999,25.7".parse::<Climate>()?);
|
||||||
|
println!("{:?}", "".parse::<Climate>()?);
|
||||||
|
Ok(())
|
||||||
|
}
|
||||||
|
|
||||||
|
#[cfg(test)]
|
||||||
|
mod test {
|
||||||
|
use super::*;
|
||||||
|
#[test]
|
||||||
|
fn test_empty() {
|
||||||
|
let res = "".parse::<Climate>();
|
||||||
|
assert_eq!(res, Err(ParseClimateError::Empty));
|
||||||
|
assert_eq!(res.unwrap_err().to_string(), "empty input");
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_short() {
|
||||||
|
let res = "Boston,1991".parse::<Climate>();
|
||||||
|
assert_eq!(res, Err(ParseClimateError::BadLen));
|
||||||
|
assert_eq!(res.unwrap_err().to_string(), "incorrect number of fields");
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_long() {
|
||||||
|
let res = "Paris,1920,17.2,extra".parse::<Climate>();
|
||||||
|
assert_eq!(res, Err(ParseClimateError::BadLen));
|
||||||
|
assert_eq!(res.unwrap_err().to_string(), "incorrect number of fields");
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_no_city() {
|
||||||
|
let res = ",1997,20.5".parse::<Climate>();
|
||||||
|
assert_eq!(res, Err(ParseClimateError::NoCity));
|
||||||
|
assert_eq!(res.unwrap_err().to_string(), "no city name");
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_parse_int_neg() {
|
||||||
|
let res = "Barcelona,-25,22.3".parse::<Climate>();
|
||||||
|
assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
|
||||||
|
let err = res.unwrap_err();
|
||||||
|
if let ParseClimateError::ParseInt(ref inner) = err {
|
||||||
|
assert_eq!(
|
||||||
|
err.to_string(),
|
||||||
|
format!("error parsing year: {}", inner.to_string())
|
||||||
|
);
|
||||||
|
} else {
|
||||||
|
unreachable!();
|
||||||
|
};
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_parse_int_bad() {
|
||||||
|
let res = "Beijing,foo,15.0".parse::<Climate>();
|
||||||
|
assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
|
||||||
|
let err = res.unwrap_err();
|
||||||
|
if let ParseClimateError::ParseInt(ref inner) = err {
|
||||||
|
assert_eq!(
|
||||||
|
err.to_string(),
|
||||||
|
format!("error parsing year: {}", inner.to_string())
|
||||||
|
);
|
||||||
|
} else {
|
||||||
|
unreachable!();
|
||||||
|
};
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_parse_float() {
|
||||||
|
let res = "Manila,2001,bar".parse::<Climate>();
|
||||||
|
assert!(matches!(res, Err(ParseClimateError::ParseFloat(_))));
|
||||||
|
let err = res.unwrap_err();
|
||||||
|
if let ParseClimateError::ParseFloat(ref inner) = err {
|
||||||
|
assert_eq!(
|
||||||
|
err.to_string(),
|
||||||
|
format!("error parsing temperature: {}", inner.to_string())
|
||||||
|
);
|
||||||
|
} else {
|
||||||
|
unreachable!();
|
||||||
|
};
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
fn test_parse_good() {
|
||||||
|
let res = "Munich,2015,23.1".parse::<Climate>();
|
||||||
|
assert_eq!(
|
||||||
|
res,
|
||||||
|
Ok(Climate {
|
||||||
|
city: "Munich".to_string(),
|
||||||
|
year: 2015,
|
||||||
|
temp: 23.1,
|
||||||
|
})
|
||||||
|
);
|
||||||
|
}
|
||||||
|
#[test]
|
||||||
|
#[ignore]
|
||||||
|
fn test_downcast() {
|
||||||
|
let res = "São Paulo,-21,28.5".parse::<Climate>();
|
||||||
|
assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
|
||||||
|
let err = res.unwrap_err();
|
||||||
|
let inner: Option<&(dyn Error + 'static)> = err.source();
|
||||||
|
assert!(inner.is_some());
|
||||||
|
assert!(inner.unwrap().is::<ParseIntError>());
|
||||||
|
}
|
||||||
|
}
|
32
info.toml
32
info.toml
|
@ -994,3 +994,35 @@ it to the error type of the return type of the surrounding function.
|
||||||
Hint: You will need to write another implementation of `From` that has a
|
Hint: You will need to write another implementation of `From` that has a
|
||||||
different input type.
|
different input type.
|
||||||
"""
|
"""
|
||||||
|
|
||||||
|
[[exercises]]
|
||||||
|
name = "advanced_errs2"
|
||||||
|
path = "exercises/advanced_errors/advanced_errs2.rs"
|
||||||
|
mode = "test"
|
||||||
|
hint = """
|
||||||
|
This exercise demonstrates a few traits that are useful for custom error
|
||||||
|
types to implement. These traits make it easier for other code to consume
|
||||||
|
the custom error type.
|
||||||
|
|
||||||
|
Follow the steps in the comment near the top of the file. You will have to
|
||||||
|
supply a missing trait implementation, and complete a few incomplete ones.
|
||||||
|
|
||||||
|
You may find these pages to be helpful references:
|
||||||
|
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/define_error_type.html
|
||||||
|
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/boxing_errors.html
|
||||||
|
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/wrap_error.html
|
||||||
|
|
||||||
|
Hint: What trait must our error type have for `main()` to return the return
|
||||||
|
type that it returns?
|
||||||
|
|
||||||
|
Another hint: It's not necessary to implement any methods inside the missing
|
||||||
|
trait. (Some methods have default implementations that are supplied by the
|
||||||
|
trait.)
|
||||||
|
|
||||||
|
Another hint: Consult the tests to determine which error variants (and which
|
||||||
|
error message text) to produce for certain error conditions.
|
||||||
|
|
||||||
|
Challenge: There is one test that is marked `#[ignore]`. Can you supply the
|
||||||
|
missing code that will make it pass? You may want to consult the standard
|
||||||
|
library documentation for a certain trait for more hints.
|
||||||
|
"""
|
||||||
|
|
Loading…
Reference in New Issue