6.3) Class templates in C++

Class templates in C++ are a feature that allows you to define a generic blueprint for creating classes that work with different data types. This enables you to write a single class definition that can be used with various data types, promoting code reusability and reducing redundancy.

Here’s a detailed explanation of class templates in C++:

1. Syntax of Class Templates

A class template is defined using the template keyword followed by a template parameter list enclosed in angle brackets (<>). The template parameter(s) act as placeholders for the data types or other parameters that will be provided when creating objects of the class.

template <typename T>
class ClassName {
public:
    // Member functions and data using T
private:
    // Member variables using T
};

2. Using Class Templates

When you want to create an object of a class template, you provide the actual data type (or template parameter values) within angle brackets (<>) after the class name.

ClassName<int> obj1;       // Creates an object of ClassName with int as the template parameter
ClassName<double> obj2;    // Creates an object of ClassName with double as the template parameter

3. Member Functions of Class Templates

Member functions of a class template can use the template parameter(s) just like regular functions. They can be defined within the class template definition or outside of it.

template <typename T>
class Container {
public:
    Container(T value) : data(value) {}

    T getValue() const {
        return data;
    }

private:
    T data;
};

4. Template Type Deduction (C++17 and later)

In C++17 and later, you can use template argument deduction when creating objects of class templates, similar to function templates.

auto intContainer = Container(42);     // Deduces T as int
auto doubleContainer = Container(3.14); // Deduces T as double

5. Template Specialization

You can provide specialized implementations for specific data types within a class template. This is known as template specialization.

template <typename T>
class Container {
    // ...

    T getValue() const {
        return data;
    }
};

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

Benefits of Class Templates

• Code Reusability: Class templates allow you to create a single class definition that can be used with various data types.
• Flexibility: You can create generic classes that work with different data types or configurations.
• Standard Library: The C++ Standard Library extensively uses class templates to provide generic data structures and algorithms.

Class templates are a fundamental feature of C++ that enable the creation of flexible and reusable code. They are widely used to create generic container classes, algorithms, and libraries that can adapt to different data types and scenarios.