为rocket.rs提供的额外宏

派生 FromRequest

use rocket_extra_codegen::FromRequest;

#[derive(FromRequest)]
struct BookingService {
    db_conn: DbConnection,
    queue_conn: QueueConnection,
    user: AuthUser,
}

各个字段的错误将被通过From特质转换为通用的目标错误类型。目标错误类型默认为()，但可以手动覆盖

use rocket_extra_codegen::FromRequest;

#[derive(FromRequest)]
#[error_type = "MyError"]
struct BookingService {
    db_conn: DbConnection,
    queue_conn: QueueConnection,
    user: AuthUser,
}