How to handle multiple result and option

We have many way to handle returned value, let's sum it up here so we can recall them when needed.

How to handle multiple Result.

fn main() {
    // Result
    println!("---- Result ----");
    let random_results = vec![Some(1), Some(2), None];

    let filter_results = random_results
        .filter(|e| e.is_some())

    let filter_map_results = random_results
        .filter_map(|e| e.as_ref())

    let flat_map_results = random_results.iter().flat_map(|e| e).collect::<Vec<_>>();

    let flatten_results = random_results.iter().flatten().collect::<Vec<_>>();

    println!("filter_results: {:?}", filter_results);
    println!("filter_map_results: {:?}", filter_map_results);
    println!("flat_map_results: {:?}", flat_map_results);
    println!("flatten_results: {:?}", flatten_results);

    // Option
    println!("---- Option---- ");
    let random_options = vec![Some(1), Some(2), None];

    let filter_map_err_options = random_options
        .filter_map(|r| match r {
            Some(r) => Some(r),
            None => None,

    let flat_map_options = random_options.iter().flat_map(|e| e).collect::<Vec<_>>();

    let flatten_options = random_options.iter().flatten().collect::<Vec<_>>();

    println!("filter_map_err_options: {:?}", filter_map_err_options);
    println!("flatten_options: {:?}", flatten_options);
    println!("flat_map_options: {:?}", flat_map_options);
    println!("flatten_options: {:?}", flatten_options);

How to convert between Result and Option

fn main() {
     // How to convert from `Result` to `Option`.
    let random_results = vec![Ok(1), Ok(2), Err(3)];
    println!("1️⃣ random_results: {:?}", random_results);

    let map_option_foo = random_results.iter().map(|e| e.ok()).collect::<Vec<_>>();
    println!("2️⃣ map_option_foo: {:?}", map_option_foo);

    // How to convert from `Option` to `Result`.
    let random_options = vec![Some(1), Some(2), None];
    println!("3️⃣ random_options: {:?}", random_options);

    let map_result_foo = random_options
        .map(|e| e.ok_or("Error!!!"))

    println!("4️⃣ map_result_foo: {:?}", map_result_foo);

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