Rustのok_orの便利の使い方

There are many methods can be used to check if an Option has value. For examples:

Use is_some() or is_none():

    if x.is_some() {
        println!("test_with_if i is {:?}", x.unwrap());
    }

Use match:

    match x {
        None => {}
        Some(i) => {
            println!("test_with_match i is {:?}", i);
        }
    }

Use if let:

    if let Some(i) = x {
        println!("test_with_if_let i is {:?}", i);
    };

Or if ok_or to convert it to Result type and then process as Result:

    let _ = x.ok_or(NotFoundError).and_then(|i| {
        println!("test_with_ok_or i is {:?}", i);
        Ok(i)
    });

すべてのコードは　ここ