Classes and Objects are part of object-oriented methods and typically provide features such as properties and methods. One of the great features of an object orientated language like C++ is a copy assignment operator that is used with operator= to create a new object from an existing one. In this post, we explain what a copy assignment operator is and its types in usage with some C++ examples.
Table of Contents
What is a copy assignment operator in C++?
The Copy Assignment Operator in a class is a non-template non-static member function that is declared with the operator=. When you create a class or a type that is copy assignable (that you can copy with the = operator symbol), it must have a public copy assignment operator. Here is a simple syntax for the typical declaration of a copy assignment operator which is defaulted:
Syntax (Since C++11).
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class_name & class_name :: operator= ( const class_name& ) = default; |
Here is an example in a class.
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Tmyclass& operator=(const Tmyclass& other) = default; // Copy Assignment Operator |
Is there a simple example of using the copy assignment operator in C++?
The forced copy assignment operator is default in any class declarations. This means you don’t need to declare it as above. Let’s give examples without using it.
Let’s give a simple C++ example to copy assignment operator with default option, here is a simple class:
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class myclass { public: std::string str; }; |
Because this is default in any class declaration, and it is automatically declared. This class is same as below.
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class myclass { public: std::string str; Tmyclass& operator=(const Tmyclass& other) = default; // Copy Assignment Operator }; |
And here is how you can use this “=” copy assignment operator with both class examples above.
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Tmyclass o1, o2; o2 = o1; // Using Copy Assignment Operator |
now let’s see different usage types in C++,
1. Typical Declaration of A Copy Assignment Operator with Swap
2. Typical Declaration of A Copy Assignment Operator ( No Swap)
3. Forced Copy Assignment Operator
4. Avoiding Implicit Copy Assignment
5. Implicitly-declared copy assignment operator
6. Deleted implicitly declared copy assignment operator
7. Trivial copy assignment operator
8. Eligible copy assignment operator
9. Implicitly-defined copy assignment operator
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