The Ultimate Guide to Rust Programming/

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Pattern Matching

Pattern Matching

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Let’s write a function to produce a greeting for someone based on their job. Here’s one naive approach using if/else:

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impl Person {
    fn greeting(&self) -> String {
        if self.job == Job::Teacher {
            format!("Hello, you're a teacher named {}", self.name)
        } else if self.job == Job::Scientist {
            format!("Hello, you're a scientist named {}", self.name)
        } else {
            format!("Huh, this shouldn't be possible...")
        }
    }
}

There are two problems with this approach:

  • I had to add a bogus else clause at the end to handle the possibility that the person is neither a teacher nor a scientist. However, we know that can never happen! Nonetheless, if I leave that off, the compiler complains. That’s annoying.

  • If in the future you decide to add a new job (maybe a plumber), ...