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https://github.com/ahgamut/rust-ape-example.git
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52 lines
1.1 KiB
Rust
52 lines
1.1 KiB
Rust
// ./src/error/multiple_error_types/boxing_errors.md
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use std::error;
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use std::fmt;
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// Change the alias to `Box<error::Error>`.
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type Result<T> = std::result::Result<T, Box<dyn error::Error>>;
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#[derive(Debug, Clone)]
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struct EmptyVec;
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impl fmt::Display for EmptyVec {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "invalid first item to double")
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}
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}
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impl error::Error for EmptyVec {}
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fn double_first(vec: Vec<&str>) -> Result<i32> {
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vec.first()
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.ok_or_else(|| EmptyVec.into()) // Converts to Box
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.and_then(|s| {
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s.parse::<i32>()
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.map_err(|e| e.into()) // Converts to Box
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.map(|i| 2 * i)
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})
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}
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fn print(result: Result<i32>) {
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match result {
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Ok(n) => println!("The first doubled is {}", n),
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Err(e) => println!("Error: {}", e),
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}
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}
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fn part0() {
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let numbers = vec!["42", "93", "18"];
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let empty = vec![];
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let strings = vec!["tofu", "93", "18"];
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print(double_first(numbers));
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print(double_first(empty));
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print(double_first(strings));
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}
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pub fn main() {
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part0();
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}
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