Chapter 3: Page 72 - Needs "as"

[krzkrzkrz]

The book has in Listing 3.7:

let new_course = Course {
    tutor_id: new_course.tutor_id,
    course_id: Some(course_count_for_user + 1),
    course_name: new_course.course_name.clone(),
    posted_time: Some(Utc::now().naive_utc()),
};

Rust compiler returns with an error:

course_id: Some(course_count_for_user + 1),
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `usize`

Since the .count returns a usize and course_id was defined as an Option of i32 (i.e. Option<i32>):

let course_count_for_user = app_state
        ...
        .count(); // returns a usize

The value for course_id needs to be changed to:

course_id: Some((course_count_for_user + 1) as i32),