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Learn About Implicitly-Defined Copy Constructor

Do you want to define a copy constructor in a implicit way ? Implicitly-Defined Copy Constructor helps you to do this, here is the full post;

The Constructor in C++ is a function, a method in the class, but it is a ‘special method’ that is automatically called when an object of a class is created. We don’t need to call this function. Whenever a new object of a class is created, the Constructor allows the class to initialize member variables or allocate storage. This is why the name Constructor is given to this special method. Here is a simple constructor class example below,

There are different constructor types in classes and the Copy Constructor is one of these. Copy Constructors not only used in classes but also used with struct and union data types.

The Copy Constructor in classes (class_name) is a non-template constructor whose first parameter is class_name&‍, const class_name&‍, volatile class_name&‍, or const volatile class_name&‍ . It can be used with no other parameters or with the rest of the parameters all have default values.

The Copy Constructor is a constructor type for classes that class_name must name the current class, or it should be a qualified class name when it is declared at namespace scope or in a friend declaration.

Implicitly-Defined Copy Constructor

The implicitly-defined copy constructor is defined by the compiler if Implicitly Declared Copy Constructor is not deleted. In union types this implicitly-defined copy constructor copies the object representation by using std::memmove statement. In other non-union class types (like classes and structs), their constructor performs full member-wise copy of the object’s bases and non-static members, in their initialization order, using direct initialization. Remember that copy constructor has this syntax,

and this Copy Constructor will be defined implicitly when declaring a new class as below,

The generation of the implicitly-defined copy constructor is deprecated if T has a user-defined destructor or user-defined copy assignment operator.

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About author

Dr. Yilmaz Yoru has 33+ years of coding with more than 30+ programming languages, mostly C++ on Windows, Android, Mac-OS, iOS, Linux, and some other operating systems. He was born in 1974, Eskisehir-Turkey, started coding in college and graduated from the department of Mechanical Engineering of Eskisehir Osmangazi University in 1997. He worked as a research assistant at the same university for more than 10 years. He received his MSc and PhD degrees from the same department at the same university. Since 2012, he is the founder and CEO of Esenja LLC Company. He has married and he is a father of a son. Some of his interests are Programming, Thermodynamics, Fluid Mechanics, Artificial Intelligence, 2D & 3D Designs, and high-end innovations.
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