virtual constructor an default constructor in C++

virtual constructor in C++

Fundamental

1. Why do we not have a virtual constructor in C++?

Why does C++ not have a virtual constructor?

From Bjarne Stroustrup's C++ Style and Technique FAQ Why don't we have virtual constructors?

A virtual call is a mechanism to get work done given partial information. In particular, "virtual" allows us to call a function knowing only any interfaces and not the exact type of the object. To create an object you need complete information. In particular, you need to know the exact type of what you want to create. Consequently, a "call to a constructor" cannot be virtual.

Basics

2. Constructors (C++): from Microsoft

To customize how class members are initialized, or to invoke functions when an object of your class is created, define a constructor. A constructor has the same name as the class and no return value. You can define as many overloaded constructors as needed to customize initialization in various ways. Typically, constructors have public accessibility so that code outside the class definition or inheritance hierarchy can create objects of the class. But you can also declare a constructor as protected or private.

Constructors can optionally take a member init list. This is a more efficient way to initialize class members than assigning values in the constructor body. The following example shows a class Box with three overloaded constructors. The last two use member init lists:

3. Advanced C++ | Virtual Constructor

The virtual mechanism works only when we have a base class pointer to a derived class object.

In C++, the constructor cannot be virtual, because when a constructor of a class is executed there is no virtual table in the memory, means no virtual pointer defined yet. So, the constructor should always be non-virtual.

But virtual destructor is possible..

4. The constructor function in a pure virtual class should be “protected” or “public”?

This is a paragraph.

5. C++ default constructor

key note:A class constructor is a special member function of a class that is executed whenever we create new objects of that class.

A constructor will have exact same name as the class and it does not have any return type at all, not even void. Constructors can be very useful for setting initial values for certain member variables..

6. Constructors in C++

What is constructor? A constructor is a member function of a class which initializes objects of a class. In C++, Constructor is automatically called when object(instance of class) create. It is special member function of the class.

7. Initializing objects on the fly

I have a vector called players and a class called Player. And what I'm trying to do is to write:

players.push_back(Player(name, Weapon(bullets)));
8. Constructors in C++11

The object life cycle involves three activities: creation, destruction, and assignment. It is important to understand how and when objects are created, destroyed, and assigned, and how you can customize these behaviours.

Objects are created at the point you declare them (if they’re on the stack) or when you explicitly allocate space for them with new or new[]. When an object is created, all its embedded objects are also created. For example:.

C++ optimizations

9. 3: C++ Optimizations You Can Do "As You Go"

Defy the software engineering mantra of "optimization procrastination." These techniques can be added to your code today! In general, these methods not only make your code more efficient, but increase readability and maintainability, too.

10. C++ Optimization Strategies and Techniques - Pete Isensee

Many software engineers recommend what I call the "procrastination approach" to optimization. Delay optimization as much as possible, and don't do it if you can avoid it. I agree with the basic premise. Optimizing too early or too often is not a good approach to engineering. Better to have a program that runs than a fast program that crashes. On the other hand, you're not likely to write a successful app these days without doing optimization at some point in the process. Your compiler can help you, but you as a programmer understand more about your application than the compiler. As Michael Abrash puts it, the best compiler is "between your ears."

There are many levels of optimization, but I'm going to focus on one in particular: C++ optimizations. Some of these techniques apply to other languages as well - like Java - but most are specific to C++. I'll also cover how to configure your compiler for maximum C++ efficiency.

Advanced Constructors

11. C++ Explained: Object initialization and assignment, lvalues and rvalues, copy and move semantics and the copy-and-swap idiom

In this article I’m going to try and clear up some fundamental C++ topics which are a common source of confusion for beginning and intermediate C++ programmers, and programmers coming to C++ from other languages such as C# or Java:

• the difference between initialization and assignment, which uses of the “=” operator trigger initialization and which trigger assignment, and how to implement them correctly in your own classes
• the meaning of lvalues, rvalues and rvalue references and how to spot which is which in your programs
• an introduction to C++11 move semantics
• when copy and move constructors and assignment operators are called in your classes, and how to implement them
• reducing the amount of duplicated and error-prone code in constructor and assignment operator implementations by using the so-called copy-and-swap idiom.
12. Constructors

ISO FAQs