87 lines
2.1 KiB
Rust
87 lines
2.1 KiB
Rust
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// errors6.rs
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// Using catch-all error types like `Box<dyn error::Error>` isn't recommended
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// for library code, where callers might want to make decisions based on the
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// error content, instead of printing it out or propagating it further. Here,
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// we define a custom error type to make it possible for callers to decide
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// what to do next when our function returns an error.
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// Make these tests pass! Execute `rustlings hint errors6` for hints :)
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// I AM NOT DONE
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// This is a custom error type that we will be using in `parse_pos_nonzero()`.
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#[derive(PartialEq, Debug)]
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enum ParsePosNonzeroError {
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CreationError,
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ParseIntError
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}
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fn parse_pos_nonzero(s: &str)
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-> Result<PositiveNonzeroInteger, ParsePosNonzeroError>
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{
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// TODO: change this to return an appropriate error instead of panicking
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// when `parse()` returns an error.
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let x: i64 = s.parse().unwrap();
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PositiveNonzeroInteger::new(x)
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.or(Err(ParsePosNonzeroError::CreationError))
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}
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// Don't change anything below this line.
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#[derive(PartialEq, Debug)]
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struct PositiveNonzeroInteger(u64);
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#[derive(PartialEq, Debug)]
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enum CreationError {
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Negative,
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Zero,
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}
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impl PositiveNonzeroInteger {
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fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
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match value {
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x if x < 0 => Err(CreationError::Negative),
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x if x == 0 => Err(CreationError::Zero),
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x => Ok(PositiveNonzeroInteger(x as u64))
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}
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_parse_error() {
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assert_eq!(
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parse_pos_nonzero("not a number"),
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Err(ParsePosNonzeroError::ParseIntError)
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);
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}
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#[test]
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fn test_negative() {
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assert_eq!(
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parse_pos_nonzero("-555"),
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Err(ParsePosNonzeroError::CreationError)
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);
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}
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#[test]
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fn test_zero() {
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assert_eq!(
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parse_pos_nonzero("0"),
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Err(ParsePosNonzeroError::CreationError)
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);
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}
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#[test]
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fn test_positive() {
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assert_eq!(
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parse_pos_nonzero("42"),
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Ok(PositiveNonzeroInteger(42))
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);
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}
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}
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