Rustlings error6.rs

[iHichew]

寻求一下rustlings error_handling 部分的error6.rs的解答思路
(Rustings好像这一部分有变化，有的版本可能没有error6)
题目链接：
https://github.com/rust-lang/rustlings/blob/main/exercises/error_handling/errors6.rs

[MorningGloryy]

我在这个页面做了解答并测试通过：https://codechina.csdn.net/u011732390/morningglory/-/tree/master/step0/errors/error6
star please

[MorningGloryy]

impl ParsePosNonzeroError {
fn from_creation(err: CreationError) -> ParsePosNonzeroError {
ParsePosNonzeroError::Creation(err)
}
// TODO: add another error conversion function here.
fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
ParsePosNonzeroError::ParseInt(err)
}
}

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.
match s.parse() {
Ok(x) => {match PositiveNonzeroInteger::new(x) {
Ok(PositiveNonzeroInteger(x)) => Ok(PositiveNonzeroInteger(x)),
Err(CreationError::Negative) => Err(ParsePosNonzeroError::from_creation(CreationError::Negative)),
Err(CreationError::Zero) => Err(ParsePosNonzeroError::from_creation(CreationError::Zero)),
}
}
Err(ParseIntError) => Err(ParsePosNonzeroError::from_parseint(ParseIntError)),
}

}

[sawaYch]

There are two ways to handle.

1. legacy way, using a nested match expression
2. use .map_err()

for the second way:

fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseInt)?;
    PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
}

[hscspring]

with nested match exp:

match s.parse() {
    Ok(x) => PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::Creation),
    Err(err) => Err(ParsePosNonzeroError::ParseInt(err)),
}