C++: Practice: Address Book System
Last updated: 2026-08-26
In lesson 50, we learned about unit testing.
Now, we'll build our first comprehensive practical project — an address book system.
This project will integrate all the knowledge you've learned so far.
1. Project Requirements
(1) 1.1 Functional Requirements
| Feature | Description |
|---|---|
| Add contact | Enter name, phone, email |
| Delete contact | Delete by name or phone |
| Modify contact | Update information |
| Find contact | Search by name or phone |
| Display all | List all contacts |
| Save/Load | Persist to file |
(2) 1.2 Class Design
TEXT
📖 Display only
Contact
- name, phone, email
AddressBook
- vector<Contact> contacts
- add, remove, update, find, display
- save, load
2. Contact Class
(1) 2.1 Contact Class Definition
TEXT
📖 Display only
#include <iostream>
#include <string>
#include <fstream>
class Contact {
private:
std::string name;
std::string phone;
std::string email;
public:
Contact() = default;
Contact(const std::string& name, const std::string& phone, const std::string& email)
: name(name), phone(phone), email(email) {}
// Getter
std::string getName() const { return name; }
std::string getPhone() const { return phone; }
std::string getEmail() const { return email; }
// Setter
void setName(const std::string& n) { name = n; }
void setPhone(const std::string& p) { phone = p; }
void setEmail(const std::string& e) { email = e; }
// Display
void display() const {
std::cout << "Name: " << name << std::endl;
std::cout << "Phone: " << phone << std::endl;
std::cout << "Email: " << email << std::endl;
std::cout << "-------------------" << std::endl;
}
// Serialize (save to file)
void save(std::ofstream& file) const {
file << name << "," << phone << "," << email << std::endl;
}
// Deserialize (load from file)
static Contact load(std::ifstream& file) {
Contact c;
std::getline(file, c.name, ',');
std::getline(file, c.phone, ',');
std::getline(file, c.email);
return c;
}
};
3. Address Book Class
(1) 3.1 AddressBook Class Definition
▶ Example 1: Using STL Containers (Difficulty ⭐)
CPP
📖 Display only
#include <vector>
#include <algorithm>
class AddressBook {
private:
std::vector<Contact> contacts;
public:
// Add contact
void addContact(const Contact& c) {
contacts.push_back(c);
std::cout << "Added successfully!" << std::endl;
}
// Find contact (by name)
Contact* findByName(const std::string& name) {
for (auto& c : contacts) {
if (c.getName() == name) {
return &c;
}
}
return nullptr;
}
// Delete contact (by name)
bool removeByName(const std::string& name) {
auto it = std::remove_if(contacts.begin(), contacts.end(),
[&name](const Contact& c) {
return c.getName() == name;
});
if (it != contacts.end()) {
contacts.erase(it, contacts.end());
std::cout << "Deleted successfully!" << std::endl;
return true;
}
std::cout << "Contact not found: " << name << std::endl;
return false;
}
// Display all contacts
void displayAll() const {
if (contacts.empty()) {
std::cout << "Address book is empty" << std::endl;
return;
}
for (const auto& c : contacts) {
c.display();
}
}
// Save to file
void saveToFile(const std::string& filename) const {
std::ofstream file(filename);
if (!file) {
std::cerr << "Cannot open file" << std::endl;
return;
}
for (const auto& c : contacts) {
c.save(file);
}
file.close();
std::cout << "Saved successfully!" << std::endl;
}
// Load from file
void loadFromFile(const std::string& filename) {
std::ifstream file(filename);
if (!file) {
std::cerr << "Cannot open file" << std::endl;
return;
}
contacts.clear(); // Clear existing data
std::string line;
while (file.peek() != EOF) {
contacts.push_back(Contact::load(file));
}
file.close();
std::cout << "Loaded successfully!" << std::endl;
}
};
Output:
TEXT
📖 Display only
Added successfully!
Deleted successfully!
Contact not found:
Address book is empty
Saved successfully!
Loaded successfully!
4. Main Menu
(1) 4.1 Menu Implementation
TEXT
📖 Display only
void showMenu() {
### ▶ Example 2: Basic Programming Practice (Difficulty ⭐)
std::cout << "\n===== Address Book Management System =====" << std::endl;
std::cout << "1. Add contact" << std::endl;
std::cout << "2. Delete contact" << std::endl;
std::cout << "3. Find contact" << std::endl;
std::cout << "4. Display all contacts" << std::endl;
std::cout << "5. Save" << std::endl;
std::cout << "6. Load" << std::endl;
std::cout << "0. Exit" << std::endl;
std::cout << "==========================================" << std::endl;
std::cout << "Choose: ";
}
int main() {
AddressBook book;
int choice;
do {
showMenu();
std::cin >> choice;
switch (choice) {
case 1: {
std::string name, phone, email;
std::cout << "Name: ";
std::cin >> name;
std::cout << "Phone: ";
std::cin >> phone;
std::cout << "Email: ";
std::cin >> email;
book.addContact(Contact(name, phone, email));
break;
}
case 2: {
std::string name;
std::cout << "Name: ";
std::cin >> name;
book.removeByName(name);
break;
}
case 3: {
std::string name;
std::cout << "Name: ";
std::cin >> name;
Contact* c = book.findByName(name);
if (c) {
c->display();
} else {
std::cout << "Not found" << std::endl;
}
break;
}
case 4:
book.displayAll();
break;
case 5: {
book.saveToFile("contacts.txt");
break;
}
case 6: {
book.loadFromFile("contacts.txt");
break;
}
case 0:
std::cout << "Goodbye!" << std::endl;
break;
default:
std::cout << "Invalid choice" << std::endl;
}
} while (choice != 0);
return 0;
}
5. Extension Suggestions
(1) 5.1 Feature Extensions
| Feature | Difficulty |
|---|---|
| Search by phone | ⭐ |
| Modify contact | ⭐⭐ |
| Sort by name | ⭐⭐ |
| Import/Export CSV | ⭐⭐⭐ |
| GUI | ⭐⭐⭐⭐ |
❓ Exercises
(1) Basic Exercise (Difficulty ⭐)
Add a "search by phone" feature to the address book.
(2) Intermediate Exercise (Difficulty ⭐⭐)
Add a "modify contact" feature to the address book.
(3) Challenge Exercise (Difficulty ⭐⭐⭐)
Refactor the address book using std::map to improve search efficiency.
▶ Example 3: Contact Struct Definition (Difficulty ⭐)
CPP
#include <iostream>
#include <string>
struct Contact {
std::string name;
std::string phone;
std::string email;
void display() const {
std::cout << "Name: " << name << std::endl;
std::cout << "Phone: " << phone << std::endl;
std::cout << "Email: " << email << std::endl;
}
};
int main() {
Contact c1 = {"Zhang San", "13800138000", "zhangsan@example.com"};
Contact c2 = {"Li Si", "13900139000", "lisi@example.com"};
c1.display();
std::cout << "---" << std::endl;
c2.display();
return 0;
}
Output:
TEXT
📖 Display only
Name:
Phone:
Email:
---
❓ FAQ
Q Why use vector instead of arrays?
A vector automatically resizes, so you don't need to know the number of elements in advance. Array size must be determined at compile time, while vector can flexibly grow and shrink at runtime.
Q Why use a struct for contact info instead of multiple arrays?
A Structs package related data together, making the logic clearer. With multiple arrays, add/delete operations are error-prone (e.g., deleting a name but forgetting to delete the phone).
Q What should I watch out for with file I/O?
A ① Check if the file opened successfully (is_open); ② Close after writing (close()); ③ Use eof() or good() in read loops to avoid infinite loops; ④ Use exception handling to ensure files are properly closed.
📖 Summary
| Knowledge Point | Application |
|---|---|
| Object-Oriented | Contact and AddressBook classes |
| STL | vector for storing contacts |
| File Operations | Save/Load |
| String Processing | Parse CSV |
- Address book system: four core CRUD operations
- Use structs to store contact information
- Vector container for managing dynamic data
- File I/O for data persistence
- Modular functions encapsulate each feature
📝 Exercises
-
Basic (Difficulty ⭐): Run the address book program, add 3 contacts (name, phone, group), and view the display. Try using the "edit" feature to modify one contact's information.
-
Intermediate (Difficulty ⭐⭐): Add a "favorite contact" feature to the address book — add a
bool isFavoritefield to the struct, and mark favorite contacts with[★]when displaying the list. -
Challenge (Difficulty ⭐⭐⭐): Implement a "fuzzy search" feature: after the user enters a keyword, match all contacts whose names contain the keyword and display them. If the input is empty, show all contacts. Support case-insensitive matching.
Next lesson: Practice: Simple Database (#52)
