【转】Options in Rust

原文：https://www.educative.io/edpresso/options-in-rust

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The Option<T> enum in Rust can cater to two variants:

• None: represents a lack of value or if an error is encountered
• Some(value): value with type T wrapped in a tuple

Code

Let’s look at a case where the Option enum could come in handy. The work_experience function below uses a match operator to return either values or a None object based on a person’s occupation.

 

 

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fn work_experience(occupation: &str) -> Option<u32>{   match occupation{     "Junior Developer" => Some(5),     "Senior Developer" => Some(10),     "Project Manager" => Some(15),     _ => None   } }     fn main() {   println!("Years of work experience for a junior developer: {}", match work_experience("Junior Developer"){     Some(opt) => format!("{} years", opt),     None => "0 years".to_string()   });     println!("\nYears of work experience for a student: {}", match work_experience("Student"){     Some(opt) => format!("{} years", opt),     None => "0 years".to_string()   }); }