Struct

You can create your own composite types using a struct. Each struct describes a type that is made up of fields. When you create a variable of this type is has space for each field, allowing you to access it as a whole or to access each field separately.

Annotated book_data struct and example variables

A struct:

• Is a building block that you can create and use in your code.
• Is a declaration of a new type - you can use this to create variables, parameters, and return these values from functions.
• Contains fields that will exist within the variables you create using this type.

When you use a struct:

• You access fields of the variable using the dot (.) operator.
• You can pass and return all values at once - using a struct value.

Example

In this program we create a new book_data type. This means we can create and work with values that represent books within our program.

#include "splashkit.h"

// Access read_integer and read_string in utilities
#include "utilities.h"

using std::to_string;

/**
 * Book data captures details for a single book.
 *
 * @field title  the title of the book
 * @field pages  the number of pages in the book
 */
typedef struct book_data
{
    string title;
    int pages;
} book_data;

/**
 * Output details of a book to the terminal
 *
 * @param book the book to output
 */
void print_book(book_data book)
{
    // Access fields of the book to get details
    write_line(book.title + " (" + to_string(book.pages) + " pages)");
}

/**
 * Read in the details of the book from the terminal
 *
 * @param prompt a message to show the user when they start
 *               to enter the book data
 * @return a book populated with the data the user provided
 */
book_data read_book(string prompt)
{
    // Create a book variable, and initialise it
    book_data result = {"", 0};

    write_line(prompt);

    // Store data into result's title
    result.title = read_string("Enter book title: ");

    // Store data into result's pages
    result.pages = read_integer("Enter number of pages: ");

    return result;
}

int main()
{
    // Initialise book_0
    book_data book_0 = {"Happy Days", 20};
    book_data book_1;
    book_data book_2;

    // Read in book data, and store in variables
    book_1 = read_book("Enter book 1 details.");
    book_2 = read_book("Enter book 2 details.");

    // Pass in the book data to have it printed
    print_book(book_0);
    print_book(book_1);
    print_book(book_2);

    return 0;
}