How to Efficiently Initialize Abstract Class Variables in C+ + Constructors

Discover a clean, efficient method to initialize abstract class variables in C+ + constructors using dynamic polymorphism.
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This video is based on the question https://stackoverflow.com/q/65329846/ asked by the user 'J Agustin Barrachina' ( https://stackoverflow.com/u/5931672/ ) and on the answer https://stackoverflow.com/a/65332129/ provided by the user 'Eugene' ( https://stackoverflow.com/u/459565/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Efficiently Initialize Abstract Class Variables in C+ + Constructors: A Complete Guide

When working with abstract classes in C+ + , you may encounter specific challenges related to initialization—especially when you want to create objects of derived classes and set them as member variables. This thoughtful guide aims to address the common problem many developers face when trying to define an abstract class in the constructor of a class, while ensuring clean and effective code. Let's dive into the details!

The Problem at Hand

Imagine you have a class called Example which contains a variable named child. This child can either be an object of Child1 or Child2, both of which derive from an abstract class called Father. The main challenge here is that you cannot directly instantiate Father since it’s abstract.

The previous attempts you might have made could look something like this:

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Clearly, this doesn’t work, so it leads to a question: Is there a better way to do this? In the following sections, we'll explore a more elegant solution.

Understanding Dynamic Polymorphism

To resolve this issue, we need to take advantage of dynamic polymorphism. This programming principle allows you to use pointers (or smart pointers) to refer to objects of derived classes. Here’s how we can implement it:

Step 1: Use Smart Pointers

Instead of trying to create an instance of Father, we will declare child as a pointer, preferably a smart pointer, to ensure memory management is handled efficiently.

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Step 2: Instantiate Child Classes in the Constructor

In the constructor, we can now use a conditional statement to decide which derived class object to create. Here’s how it can be implemented:

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Full Example Code

Putting it all together, your complete code for the Example class could look like this:

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Conclusion

In summary, when dealing with abstract variables in C+ + , the recommended approach is to utilize pointers (or smart pointers) to refer to derived class objects. This method not only allows you to comply with C+ + inheritance rules but also enhances memory safety and code clarity. By adopting practices such as these, you can write cleaner, more efficient code that is easier to maintain.

Hopefully, this guide has clarified how to initialize an abstract variable in the constructor and provided insights into dynamic polymorphism in C+ + . Happy coding!

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