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C++ Class Templates

Class templates are a cornerstone of generic programming in C++. They allow you to create classes that can work with different data types without repeating code. This powerful feature enhances code reusability and flexibility.

Understanding Class Templates

A class template is a blueprint for creating classes that can operate on various data types. It's defined using the template keyword, followed by template parameters enclosed in angle brackets.

Basic Syntax

template <typename T>
class ClassName {
    // Class members using type T
};

Here, T is a placeholder for the actual data type, which is specified when the class is instantiated.

Creating and Using Class Templates

Let's explore a practical example of a class template for a simple stack data structure:

template <typename T>
class Stack {
private:
    vector<T> elements;

public:
    void push(T const& element) {
        elements.push_back(element);
    }

    T pop() {
        if (elements.empty()) {
            throw out_of_range("Stack<T>::pop(): empty stack");
        }
        T top = elements.back();
        elements.pop_back();
        return top;
    }

    bool empty() const {
        return elements.empty();
    }
};

This Stack class can now be used with any data type:

Stack<int> intStack;
intStack.push(5);
intStack.push(10);

Stack<string> stringStack;
stringStack.push("Hello");
stringStack.push("World");

Multiple Template Parameters

Class templates can have multiple parameters, allowing for even more flexibility:

template <typename T, typename U>
class Pair {
    T first;
    U second;
public:
    Pair(T f, U s) : first(f), second(s) {}
    // ... other methods
};

Pair<int, string> myPair(1, "One");

Template Specialization

Sometimes, you might want to provide a specialized implementation for a specific data type. This is called template specialization:

template <>
class Stack<bool> {
    // Specialized implementation for bool
};

For more details on this topic, check out the guide on C++ Template Specialization.

Best Practices and Considerations

  • Use class templates to create generic, reusable code.
  • Be mindful of code bloat when using templates excessively.
  • Consider using C++ Concepts (C++20) to constrain template parameters.
  • Remember that template code is typically implemented in header files.
  • Use meaningful names for template parameters (e.g., ElementType instead of just T).

Conclusion

Class templates are a powerful feature in C++ that enable generic programming. They allow you to write flexible, type-safe code that works with multiple data types. By mastering class templates, you can significantly improve your C++ programming skills and create more efficient, reusable code.

To further enhance your C++ knowledge, explore related topics such as C++ Function Templates and C++ Variadic Templates.