Working With Rust Result - Summary

If you’ve made it this far, you’re probably overwhelmed by all the different methods and their uses! It helps to try and learn to use them one at a time; as and when needed.

Cheatsheet

The following table summarises which method you would use under different circumstances.

What do you want to do?	Method to use
Create a `Result`	Constructor: `Ok(value)` Constructor: `Err(value)`
Get both values out of a `Result`	`Patten matching` `map_or_else` `map_or` eager `unwrap` panics `unwrap_or` eager `unwrap_or_else` `unwrap_or_default` `expect` panics
Run a function on the value inside `Ok`	`map` `and_then`
Run a function on the value inside `Err`	`or_else` `map_err`
Get the value inside `Ok`	`unwrap` panics `expect` panics `? operator`
Get the value inside `Ok` with fallback	`Patten matching` `map_or` eager `unwrap_or` eager `unwrap_or_else` `unwrap_or_default`
Get the value inside `Err`	`unwrap_err` panics `expect_err` panics
Get the value inside `Err` with fallback	`Patten matching` `map_or` eager `unwrap_or` eager `unwrap_or_else` `unwrap_or_default`
Combine two `Result`s that are `Ok`	`and_then` `and` eager `? operator`
Combine two `Result`s that are `Err`	`or` eager `or_else`
Convert `Ok` to `Option` as `Some`	`ok`
Convert `Err` to `Option` as `Some`	`err`
Convert `Result<Option>` to `Option<Result>`	`transpose`
Test for `Ok`	`is_ok`
Test for `Err`	`is_err`
Test for `Ok` and run a predicate	`is_ok_and`
Test for `Err` and run a predicate	`is_err_and`

I hope this somewhat lengthy series helped you learn some more about Rust’s Result type. If you found any errors or omissions or found this useful, please leave a comment.

Feedback from the review lounge

SirKastic23

A huge thanks to SirKastic23 for giving me some sound feedback on Reddit:

Comment
byu/ssanjs from discussion
inrust

I’ve made the updates to the sections marked “unsafe”. I’ve also made the blog “Dark Mode” by default.

tobikris

Another huge thanks to tobikris for pointing out an error with my usage of eager functions:

Comment
byu/ssanjs from discussion
inrust

I’ve added clearer warnings regarding eagerness and have updated the affected examples.

someboddy

Thanks to someboddy for suggesting linking to the individual sections. I’ve added a link to every method covered, in the TOC and in the summary page.

Comment
byu/ssanjs from discussion
inrust

Back to TOC