Dynamische Fehlertypen
Sometimes we want to allow any type of error to be returned without writing our own enum covering all the different possibilities. The std::error::Error
trait makes it easy to create a trait object that can contain any error.
Speaker Notes
This slide should take about 5 minutes.
The read_count
function can return std::io::Error
(from file operations) or std::num::ParseIntError
(from String::parse
).
Boxing errors saves on code, but gives up the ability to cleanly handle different error cases differently in the program. As such it's generally not a good idea to use Box<dyn Error>
in the public API of a library, but it can be a good option in a program where you just want to display the error message somewhere.
Make sure to implement the std::error::Error
trait when defining a custom error type so it can be boxed.