14.2 Regular struct

In Rust, a structure is defined using the struct keyword, as in the following example that defines a Book data type:

:clear

struct Book {
  title:  &'static str,
  author: &'static str,
  year:   i16,
}

We initialize an instance of a struct by setting a value for each field:

let book1 = Book {
  title: "La Nuit du carrefour",
  author: "Georges Simenon",
  year: 1931,
};

To retrieve a field’s value, we simply name the field we want to access on the instance:

(book1.title, book1.author, book1.year)

If we define the three following variables:

let title = "Mon ami Maigret";
let author = "Georges Simenon";
let year: i16 = 1949;

We can use them to create a Book instance. The names of the variables, because they match the names of the fields, will be used by the compiler to know how to initialize the Book instance:

let book3 = Book {
  title,
  author,
  year,
};

Here is the instance’s content:

(book3.title, book3.author, book3.year)

let book2 = Book {
  title: "Le Chien jaune",
  ..book1
};

Here is the result:

(book2.title, book2.author, book2.year)

For constructing an object, we do not usually use directly the curly braces syntax, but define a constructor method, named new() by convention. We will see the new() method in the next chapter.