Encapsulation best practices in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of private member access in C++

What is the output of this C++ code snippet?

C++

class Box {
private:
    int length;
public:
    Box(int l) : length(l) {}
    int getLength() { return length; }
};

int main() {
    Box b(10);
    // std::cout << b.length << std::endl; // Uncommenting this line causes error
    std::cout << b.getLength() << std::endl;
    return 0;
}

A 10

B Compilation error due to private member access

C 0

D Runtime error

💡 Hint

Private members cannot be accessed directly outside the class, but public methods can access them.

The private member 'length' cannot be accessed directly outside the class, but the public method getLength() returns its value. So the output is 10.

🧠 Conceptual

intermediate

Purpose of encapsulation in C++

Which of the following best describes the main purpose of encapsulation in C++?

A To make all class members public by default

B To hide internal data and only expose necessary parts through methods

C To allow direct access to all class members from anywhere

D To increase the size of the class objects

💡 Hint

Think about protecting data inside a class.

Encapsulation hides internal data and exposes only what is necessary through public methods, protecting data integrity.

🔧 Debug

advanced

Identify the encapsulation violation

Which option shows a violation of encapsulation best practices in C++?

C++

class Person {
public:
    std::string name;
    int age;
};

A Making data members public so they can be accessed directly

B Using private data members with public getter and setter methods

C Declaring data members as private and initializing them in constructor

D Using const methods to access data members

💡 Hint

Encapsulation means restricting direct access to data.

Making data members public allows external code to modify them directly, breaking encapsulation.

📝 Syntax

advanced

Correct syntax for private member with getter

Which option shows the correct syntax for declaring a private member and a public getter method in C++?

A class Sample { public: int value; int getValue() { return value; } private: };

B class Sample { private int value; public int getValue() { return value; } };

C class Sample { private: int value; public: int getValue() { return value; } };

D class Sample { private: int value; public: int getValue() { return value } };

💡 Hint

Check for correct use of colons, semicolons, and access specifiers.

Option C uses correct syntax: access specifiers with colons, semicolons after class, and method body with braces.

🚀 Application

expert

Number of accessible members from outside the class

Given this class, how many members can be accessed directly from outside the class?

C++

class Data {
private:
    int secret;
protected:
    int semi_secret;
public:
    int open;
    Data() : secret(1), semi_secret(2), open(3) {}
};

int main() {
    Data d;
    // Which members can be accessed directly here?
}

A 0

B 2

C 3

D 1

💡 Hint

Remember the meaning of private, protected, and public access.

Only public members can be accessed directly outside the class. Here, only 'open' is public.