Rust @programming.dev kia @lemmy.ca 12 mo. ago

Small pattern that made my code much cleaner

This is a really simple silly thing I just realized, but I noticed I have a lot code that looks something like this:

fn foo() -> Result&lt;(), Error> {
    // do something
}

fn bar() -> Option&lt;()> {
    let Ok(f) = foo() else {
        return None;
    };
}

I hated that if-statement. I realized today that I could simplify to:

fn bar() -> Option&lt;()> {
    let f = foo().ok()?;
}

And that cleaned up my code a lot. It's a tiny thing, but when it's okay to discard the error from the result, makes such a big difference when you have a lot of them!

9 comments

Do you really discard errors this often? I would say almost all of my Results get propagated to the caller via ? and handled in one place near the start of the stack.
- A lot of the time, I have these around places where I'm reading from a file. If reading causes an error, regardless of what the error is, I just return None and a new file is created.
  
  That is a terrible time to throw away the error. Best to actually check for file not exists error and created the file only then. Other errors are important to see to debug why things are failing.
  
  It is very annoying to have a tool tell you it failed to create a file when the file exists but it just cannot read it for some reason. You can spend ages jumping down the wrong rabbit whole if you don't realize what is happening.
  
  I don't get it!
  
  If the T in Result (and presumably Option) is (), then why not just use is_ok()/is_err() from the caller side?
  
  Other Tips:
  
  bool has then() and then_some() methods in std now.
  
  You can transpose() in both directions between ResultᐸOptionᐸTᐳᐳs and OptionᐸResultᐸTᐳᐳs
This is one of my favorite tricks!

Things like this make it possible to do a programming puzzle I like, where you try to write an entire program in just 1-3 line functions.
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