mirror of
https://github.com/ahgamut/rust-ape-example.git
synced 2024-05-15 01:52:42 +00:00
58 lines
1.6 KiB
Rust
58 lines
1.6 KiB
Rust
// ./src/error/multiple_error_types/define_error_type.md
|
|
|
|
|
|
use std::fmt;
|
|
|
|
type Result<T> = std::result::Result<T, DoubleError>;
|
|
|
|
// Define our error types. These may be customized for our error handling cases.
|
|
// Now we will be able to write our own errors, defer to an underlying error
|
|
// implementation, or do something in between.
|
|
#[derive(Debug, Clone)]
|
|
struct DoubleError;
|
|
|
|
// Generation of an error is completely separate from how it is displayed.
|
|
// There's no need to be concerned about cluttering complex logic with the display style.
|
|
//
|
|
// Note that we don't store any extra info about the errors. This means we can't state
|
|
// which string failed to parse without modifying our types to carry that information.
|
|
impl fmt::Display for DoubleError {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
write!(f, "invalid first item to double")
|
|
}
|
|
}
|
|
|
|
fn double_first(vec: Vec<&str>) -> Result<i32> {
|
|
vec.first()
|
|
// Change the error to our new type.
|
|
.ok_or(DoubleError)
|
|
.and_then(|s| {
|
|
s.parse::<i32>()
|
|
// Update to the new error type here also.
|
|
.map_err(|_| DoubleError)
|
|
.map(|i| 2 * i)
|
|
})
|
|
}
|
|
|
|
fn print(result: Result<i32>) {
|
|
match result {
|
|
Ok(n) => println!("The first doubled is {}", n),
|
|
Err(e) => println!("Error: {}", e),
|
|
}
|
|
}
|
|
|
|
fn part0() {
|
|
let numbers = vec!["42", "93", "18"];
|
|
let empty = vec![];
|
|
let strings = vec!["tofu", "93", "18"];
|
|
|
|
print(double_first(numbers));
|
|
print(double_first(empty));
|
|
print(double_first(strings));
|
|
}
|
|
|
|
pub fn main() {
|
|
part0();
|
|
}
|
|
|