An error that occurs during launch.

A LaunchError is returned by rocket::launch when launching an application fails for some reason.

Panics

A value of this type panics if it is dropped without first being inspected. An inspection occurs when any method is called. For instance, if println!("Error: {}", e) is called, where e: LaunchError, the Display::fmt method being called by println! results in e being marked as inspected; a subsequent drop of the value will not result in a panic. The following snippet illustrates this:

let error = rocket::ignite().launch();

// This line is only reached if launching failed. This "inspects" the error.
println!("Launch failed! Error: {}", error);

// This call to drop (explicit here for demonstration) will do nothing.
drop(error);

When a value of this type panics, the corresponding error message is pretty printed to the console. The following illustrates this:

let error = rocket::ignite().launch();

// This call to drop (explicit here for demonstration) will result in
// `error` being pretty-printed to the console along with a `panic!`.
drop(error);

Usage

A LaunchError value should usually be allowed to drop without inspection. There are two exceptions to this suggestion.

1. If you are writing a library or high-level application on-top of Rocket, you likely want to inspect the value before it drops to avoid a Rocket-specific panic!. This typically means simply printing the value.

2. You want to display your own error messages.