How do I design classes with proper invariants in C++?

When designing classes in C++, it is essential to maintain proper invariants to ensure that the objects of the class remain in a valid state throughout their lifetime. An invariant is a condition that must always hold true for an object after its construction and after any operation that modifies its state. Below is an example demonstrating how to establish and enforce invariants in C++ classes.

Example of a Class with Invariants

// Example of a simple BankAccount class with invariants class BankAccount { private: double balance; public: // Constructor to initialize balance BankAccount(double initialBalance) : balance(initialBalance) { // Invariant: balance should be non-negative assert(balance >= 0); } // Function to deposit money void deposit(double amount) { // Invariant: amount should be positive assert(amount > 0); balance += amount; // Invariant: balance should remain non-negative assert(balance >= 0); } // Function to withdraw money void withdraw(double amount) { // Invariant: amount should be positive and should not exceed balance assert(amount > 0 && amount <= balance); balance -= amount; // Invariant: balance should remain non-negative assert(balance >= 0); } // Function to get current balance double getBalance() const { return balance; } };

C++ class design invariants C++ best practices object-oriented programming

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