Updated July 1, 2023
What is Template Class in C++?
Template class, as the name suggests, is a Template for classes. C++ provides us with a way where we can create a class that will serve as a blueprint/template for future classes. A template class will have generic variables and methods of type “T”, which can later be customized to be used with different data types as per the requirement.
Definition
As per the standard definition, a template class in C++ is a class that allows the programmer to operate with generic data types. This allows the class to be used on many different data types as per the requirements without the need of being re-written for each type.
Understanding Template Class in C++
If we consider the real-world example of template class for better understanding, then we can consider this as a blueprint. If a real-estate builder is designing a township, he prepares the layout of apartments that include the generic specifications like floor plan, placement of doors, windows, etc. This blueprint can be considered to be a template class that will give us a general idea of how an apartment is going to look like from a bigger picture. This can be used to design individual flats that can be customized as per the owner’s preferences that will be specific to that apartment, but the generic template will remain common across the whole township.
The template class works on similar lines. If we are designing an enterprise application, it will have multiple entities that will represent the classes. Each class will have their specific properties and methods. However, a template can be designed that will manage to insert these entities into the database. We will be using this example in the coming sections of this article. But if we don’t use the template class, then we will have to write individual classes for Create, Retrieve, Update, Delete operations. However, by using the template class, we can get this work done by writing only a single class hence reducing a lot of time and removing the possibility of a lot of redundant duplicate code.
How does Template Class in C++ Make Working so Easy?
When working on an enterprise application, most of the times, the programmers face a scenario wherein the program structure becomes complicated as the number of model classes increases. The complexity gets further added when we implement the OOPS concepts like Inheritance and Polymorphism. In such scenarios, template classes come in very handy wherein you can reduce the lines of code you want to write for performing some operations that will remain the same across multiple classes/entities.
What Can You Do With Template Class in C++?
Using template classes, one can reduce the code complexity by defining generic operations to be performed in a template class and use this template class with multiple data types to get the required results.
For Example, if we are writing a calculator program that will have methods that take 2 input parameters, can perform addition, subtraction, multiplication, and division and return us the output.
Let us assume the initial requirement was to only develop such a program to work with natural numbers. For this purpose, you just wrote a class with the below template.
Class Calculator
{
public:
unsigned Add(unsigned num1, unsigned num2) {}
unsigned Subtract (unsigned num1, unsigned num2) {}
unsigned Multiply (unsigned num1, unsigned num2) {}
unsigned Divide (unsigned num1, unsigned num2) {}
};Now with the change of requirement, you are asked to perform similar operations for all integers (negative and positive) as well as decimal types (long).
With the current class, you will write two additional classes or edit this class to add similar functions for long and into data types as well.
However, if we were to use a template class, we will define only 1 template class that will work on generic data-type, and the data type of return value and input parameters will be determined based on whether an unsigned variable is passed or if you are passing long or int data type:
Template <class T>
Class Calculator
{
Public:
T Add (T num1, T num2) {}
T Subtract (T num1, T num2) {}
T Multiply (T num1, T num2) {}
T Divide (T num1, T num2) {}
};Working with Template Class in C++
From the Calculator example in the above section, we can use this Calculator generic class in our main function or any other area of our program with different data types as below:
void main () {
Long resultLong = Calculator.Add (20.7, 18.2);
Int resultInt = Calculator.Add (10, -15);
Unsigned resultUnsigned = Calculator.Add (10, 18);
}Here the data type of T defined in the Generic class will be determined based on the data type of input parameters passed to the functions.
Advantages of Template Class in C++
The major advantages of using template classes are as below:
- You need to define only 1 class that will work with different data types.
- At compile time, instances this template class is generated only for those data types for which the template class has been used in the program.
For example, if in the above example we are only using template class with the int data type, then the compiler will create an instance of only the int data type hence saving space that would have been utilized by implementations of Long and Unsigned data types had we written individual classes for each.
- As we have already seen, creating and using a template class will reduce the efforts and lines of code for development and will also reduce the complexity and time in debugging the program for any issues since you are working only with 1 class.
Required Template Class in C++ Skills
Creating and using template classes is very simple and doesn’t require you to have any advanced programming skills in C++. All you need to do is to analyze the classes that will have common functions and create a template class for all of them.
Why Should we use a Template Class in C++?
We should always try to incorporate template classes in our programs when we are working on an enterprise application that can change and grow in the future. This will help us in future when we are working on extending the functionalities of the program then we realize that a lot of the work will already be managed by template classes, and when the application becomes complex over the period of time, the code will still remain compact and understandable for anyone new looking on the program.
Why do we Need a Template Class in C++?
Template class works as a container that comes in very handy when multiple classes will be performing the same function in a similar way for different data types. This container will wrap the functionality in a single entity that can be utilized for different data types as per the requirement.
Another common use for the template class can be when looking to implement data structures like a linked list, stacks, queues for supporting different data types. These data structures will follow the same approach for push, pop, and traverse of elements irrespective of the data type and hence can be used by implementing a template class.
How will this Technology Help you in Career Growth?
Having a good knowledge and hands-on on concepts like a template class is what will separate you as a programmer for enterprise application from a program that has only learned to program and may not be able to adapt to a big enterprise application right away in the most optimized way.
This will also allow you to write codes with better understandability and extensibility.
Conclusion
When working and programming in any language, our aim should always be to support the reusability of our code by making it as generic as possible, keeping it modular and compact. The template classes are a great way to achieve that for classes with common similar functions.
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