Rust by Example

An Iter::map operation might fail, for example:

fn main() {

let strings = vec!["tofu", "93", "18"];

let numbers: Vec<_> = strings

.into_iter()

.map(|s| s.parse::())

.collect();

println!("Results: {:?}", numbers);

}

הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה

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Let's step through strategies for handling this.

Ignore the failed items with filter_map()

filter_map calls a function and filters out the results that are None.

fn main() {

let strings = vec!["tofu", "93", "18"];

let numbers: Vec<_> = strings

.into_iter()

.filter_map(|s| s.parse::().ok())

.collect();

println!("Results: {:?}", numbers);

}

הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה

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Fail the entire operation with collect()

Result implements FromIter so that a vector of results (Vec>) can be turned into a result with a vector (Result, E>). Once an Result::Err is found, the iteration will terminate.

fn main() {

let strings = vec!["tofu", "93", "18"];

let numbers: Result, _> = strings

.into_iter()

.map(|s| s.parse::())

.collect();

println!("Results: {:?}", numbers);

}

הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה

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This same technique can be used with Option.

Collect all valid values and failures with partition()

fn main() {

let strings = vec!["tofu", "93", "18"];

let (numbers, errors): (Vec<_>, Vec<_>) = strings

.into_iter()

.map(|s| s.parse::())

.partition(Result::is_ok);

println!("Numbers: {:?}", numbers);

println!("Errors: {:?}", errors);

}

הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה

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When you look at the results, you'll note that everything is still wrapped in Result. A little more boilerplate is needed for this.

fn main() {

let strings = vec!["tofu", "93", "18"];

let (numbers, errors): (Vec<_>, Vec<_>) = strings

.into_iter()

.map(|s| s.parse::())

.partition(Result::is_ok);

let numbers: Vec<_> = numbers.into_iter().map(Result::unwrap).collect();

let errors: Vec<_> = errors.into_iter().map(Result::unwrap_err).collect();

println!("Numbers: {:?}", numbers);

println!("Errors: {:?}", errors);

}

הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה

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