Glad to see `Option::zip` stabilized. I tend to write such a helper in many of my projects to collect optional variables together when they're coupled. Really improves the ergonomics doing more railroad-style programming.
You sometimes have two Options that must both be Some to have any effect, but other reasons prevent you from making an Option of a tuple of those two fields. Eg think of deserializing a JSON that contains optional username and password strings, but you need both if you are to use them to authenticate to some remote.
In that case, you currently have to write code like:
if let (Some(username), Some(password)) = (username, password) {
/* both are set */
}
else {
/* at least one is not set */
}
With zip this can be written as `if let Some((username, password)) = username.zip(password) {` In this case it doesn't look like a big difference, but it does allow you to chain other Option combinators more easily if you were doing that instead of writing if-let / match. Using combinators is the "railroad-style programming" that kevinastone was talking about. For example, you can more easily write:
let (username, password) = username.zip(password).ok_or("one or more required parameters is missing")?;
You could of course still do this without .zip(), but it would be clunkier:
let (username, password) = username.and_then(|username| password.map(|password| (username, password))).ok_or("one or more required parameters is missing")?;
The zip form does lose the information of which of the two original Options was None, so if you do need that information (say the error message needs to specify which parameter is missing) you'd still use the non-zip form with a match.
borgel|5 years ago
Arnavion|5 years ago
In that case, you currently have to write code like:
With zip this can be written as `if let Some((username, password)) = username.zip(password) {` In this case it doesn't look like a big difference, but it does allow you to chain other Option combinators more easily if you were doing that instead of writing if-let / match. Using combinators is the "railroad-style programming" that kevinastone was talking about. For example, you can more easily write: You could of course still do this without .zip(), but it would be clunkier: The zip form does lose the information of which of the two original Options was None, so if you do need that information (say the error message needs to specify which parameter is missing) you'd still use the non-zip form with a match.