How do lifetimes work in struct definitions

Lifetimes in struct definitions tell the compiler how long references stored in the struct must remain valid. You add a lifetime parameter to the struct and every reference field to ensure the data outlives the struct itself.

struct ImportantExcerpt<'a> {
    part: &'a str,
}

In this example, the struct ImportantExcerpt holds a reference part that must live for at least the duration 'a.

Lifetimes are like expiration dates for references stored inside a struct. They ensure that the data a struct points to doesn't disappear while the struct is still being used. Think of it as a rule that says, 'This struct can only exist as long as the data it references exists.'