Rust Programming Cookbook

How it works...

While the discussion of when to use Option and when to use Result takes place on a high level, Rust supports the transition between the two types with several functions. In addition to map(), and_then(), and so on (discussed in the Seamless error handling section in this chapter), these functions provide powerful and elegant ways to work with a variety of errors. In step 1 to step 4, we are slowly building a simple test that shows the applicability of the transpose function. It makes it possible to switch from Ok(Some(42)) to Some(Ok(42)) (notice the subtle difference) with a single call to a function. Similarly, the Err variation of the call goes from a regular Err(MyError) function to Some(Err(MyError)).

The remaining steps ...