Nested structures in C++ - Mini Project: Build & Apply

Nested structures

📖 Scenario: You are creating a simple program to store information about a book and its author. The author has a name and an age. The book has a title, a year of publication, and an author.

🎯 Goal: Build a program that uses nested structures to store and display information about a book and its author.

📋 What You'll Learn

Create a structure called Author with two members: name (string) and age (int).

Create a structure called Book with three members: title (string), year (int), and author (of type Author).

Create a variable myBook of type Book and assign the exact values: title = "The Great Adventure", year = 2020, author name = "John Smith", author age = 45.

Print the book's title, year, author's name, and author's age exactly as shown in the final output.

💡 Why This Matters

🌍 Real World

Nested structures help organize related data clearly, like storing book and author information together.

💼 Career

Understanding nested structures is important for managing complex data in software development, such as databases, file formats, and APIs.

1

Create the nested structures

Define a structure called Author with members name (string) and age (int). Then define a structure called Book with members title (string), year (int), and author (of type Author).

C++

#include 
#include 

using namespace std;

// Define Author and Book structures here

int main() {

    return 0;
}

Hint

Use struct keyword to define each structure. The Book structure should include an Author type member.

2

Create a variable with exact values

Inside main(), create a variable called myBook of type Book. Assign title to "The Great Adventure", year to 2020, author.name to "John Smith", and author.age to 45.

C++

#include 
#include 

using namespace std;

struct Author {
    string name;
    int age;
};

struct Book {
    string title;
    int year;
    Author author;
};

int main() {
    // Create myBook variable and assign values
    
    return 0;
}

Hint

Use dot notation to assign values to nested members like myBook.author.name.

3

Print the book and author details

Use cout to print the book's title, year, author's name, and author's age in this exact format:
Title: The Great Adventure
Year: 2020
Author: John Smith
Author Age: 45

C++

#include 
#include 

using namespace std;

struct Author {
    string name;
    int age;
};

struct Book {
    string title;
    int year;
    Author author;
};

int main() {
    Book myBook;
    myBook.title = "The Great Adventure";
    myBook.year = 2020;
    myBook.author.name = "John Smith";
    myBook.author.age = 45;

    // Print book and author details
    
    return 0;
}

Hint

Use cout with << to print each line exactly as shown.

4

Display the final output

Run the program and ensure it prints exactly:
Title: The Great Adventure
Year: 2020
Author: John Smith
Author Age: 45

C++

#include 
#include 

using namespace std;

struct Author {
    string name;
    int age;
};

struct Book {
    string title;
    int year;
    Author author;
};

int main() {
    Book myBook;
    myBook.title = "The Great Adventure";
    myBook.year = 2020;
    myBook.author.name = "John Smith";
    myBook.author.age = 45;

    cout << "Title: " << myBook.title << endl;
    cout << "Year: " << myBook.year << endl;
    cout << "Author: " << myBook.author.name << endl;
    cout << "Author Age: " << myBook.author.age << endl;

    // Program output should match exactly

    return 0;
}

Hint

Make sure your output matches exactly, including spaces and line breaks.

Practice

1. What is the main purpose of using nested structures in C++?

easy

A. To allow structures to inherit functions

B. To create multiple inheritance between classes

C. To increase the size of a structure unnecessarily

D. To group related data logically inside another structure

Solution

1. Step 1: Understand nested structures concept

   Nested structures let you put one structure inside another to group related data logically.

2. Step 2: Compare options

   Only To group related data logically inside another structure correctly describes grouping data logically. Other options describe unrelated concepts.

3. Final Answer:

   To group related data logically inside another structure -> Option D

4. Quick Check:

   Nested structures = group data logically [OK]

Hint: Think of nested structures as folders inside folders [OK]

Common Mistakes:

• Confusing nested structures with inheritance
• Thinking nested structures increase structure size unnecessarily
• Assuming nested structures add functions

2. Which of the following is the correct syntax to access member city inside a nested structure address within person?

easy

A. person->address.city

B. person.address.city

C. person.address->city

D. person->address->city

Solution

1. Step 1: Identify access operator for nested structures

   When accessing members of nested structures by variable (not pointer), use dot operator for each level.

2. Step 2: Apply to given example

   Since person is a variable, access address with dot, then city with dot: person.address.city.

3. Final Answer:

   person.address.city -> Option B

4. Quick Check:

   Use dot for nested struct members when variable, not pointer [OK]

Hint: Use dot operator for nested struct members if not pointers [OK]

Common Mistakes:

• Using arrow operator (->) when variable is not a pointer
• Mixing dot and arrow operators incorrectly
• Trying to access nested member directly without parent

3. What will be the output of the following code?

struct Date {
  int day;
  int month;
};
struct Event {
  char name[10];
  Date date;
};

int main() {
  Event e = {"Party", {25, 12}};
  std::cout << e.name << " on " << e.date.day << "/" << e.date.month << std::endl;
  return 0;
}

medium

A. Party on 25/12

B. Party on 12/25

C. Compilation error

D. Party on 0/0

Solution

1. Step 1: Understand structure initialization

   Event e is initialized with name "Party" and Date with day=25, month=12.

2. Step 2: Trace output statement

   Output prints e.name, then e.date.day (25), then e.date.month (12) separated by slashes.

3. Final Answer:

   Party on 25/12 -> Option A

4. Quick Check:

   Nested struct initialized correctly = Party on 25/12 [OK]

Hint: Match initialization order with nested structure fields [OK]

Common Mistakes:

• Swapping day and month values
• Assuming compilation error due to nested struct
• Forgetting to use dot operator to access nested members

4. Identify the error in the following code snippet:

struct Point {
  int x, y;
};
struct Rectangle {
  Point topLeft;
  Point bottomRight;
};

int main() {
  Rectangle rect;
  rect.topLeft->x = 0;
  rect.topLeft->y = 10;
  return 0;
}

medium

A. Using arrow operator (->) on a non-pointer structure variable

B. Missing semicolon after struct definitions

C. Incorrect member names in Rectangle

D. Rectangle struct cannot contain Point structs

Solution

1. Step 1: Check member access operators

   rect.topLeft is a structure variable, not a pointer, so dot operator (.) must be used, not arrow (->).

2. Step 2: Identify error cause

   Using -> on non-pointer causes compilation error.

3. Final Answer:

   Using arrow operator (->) on a non-pointer structure variable -> Option A

4. Quick Check:

   Use dot for struct variables, arrow for pointers [OK]

Hint: Use dot for struct variables, arrow only for pointers [OK]

Common Mistakes:

• Confusing dot and arrow operators
• Assuming arrow works for all struct members
• Ignoring compiler error messages

5. Given the following nested structures, how would you write a function printBookInfo that prints the book title and the author's city?

struct Author {
  char name[50];
  char city[30];
};
struct Book {
  char title[100];
  Author author;
};

hard

A. void printBookInfo(Book b) { std::cout << b.title << ", " << b.author->city << std::endl; }

B. void printBookInfo(Book b) { std::cout << b.title << ", " << b.city << std::endl; }

C. void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; }

D. void printBookInfo(Book b) { std::cout << b->title << ", " << b->author.city << std::endl; }

Solution

1. Step 1: Understand structure member access

   Book variable b has member title and nested structure author. Access author.city with dot operator.

2. Step 2: Check each option

   void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; } correctly uses b.title and b.author.city with dot operators. Others misuse arrow or omit author.

3. Final Answer:

   void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; } -> Option C

4. Quick Check:

   Access nested struct members with dot: b.author.city [OK]

Hint: Use dot operator for nested struct members in function parameters [OK]

Common Mistakes:

• Using arrow operator on non-pointer parameter
• Skipping nested struct name when accessing member
• Using pointer syntax incorrectly