In the C++ language, one of the features of object-oriented programming (OOP) is the copy assignment operator that is used with “operator=” to create a new object from an existing one. In this post, we explain answer the question “what is a trivial copy assignment operator in C++”.
Table of Contents
What are classes and objects in C++?
Classes are defined in C++ using keyword class followed by the name of the class. Classes are the blueprint for the objects, and they are user-defined data types that we can use in our program. Objects are an instantiation of a class. In C++ programming, most of the commands are associated with classes and objects, along with their attributes and methods. Here is a simple class example:
Now we can create our objects with this Type of myclass as shown below.
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 forced (defaulted) copy assignment operator with default option;
Syntax (Since C++11),
here is an example in a class,
This default copy assignment operator is declared automatically in a new class declaration, it is implicitly-defined or defaulted copy assignment operator and also a trivial copy assignment operator.
What is a trivial copy assignment operator in C++?
The trivial copy assignment operator is default operator 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
this is same as below,
As you see both are examples are same at runtime, because this is default in any class declaration and it is automatically declared. And here is how you can use this “=” copy assignment operator on the objects of one of these given class examples,
The trivial copy assignment operator is a default copy assignment operator that copies the given class object to a new class object. It has the same mechanics as the std::memmove method. All C language data types are trivially copy-assignable, which means the trivial copy operator is compatible with them.
When you create a simple class it has a trivial copy assignment operator.
It is trivial if the class has;
- no user-defined copy assignment operator,
- no virtual member methods or functions,
- no virtual base classes,
- the copy assignment operator selected for every direct base of this class, or every non-static class type, or every array of class type is trivial
Is there a simple example of a trivial copy assignment operator in C++?
After these useful information above, let’s give an example to trivial copy assignment operator. Lets assume that, we TmyclassA as a base class and we have a new TmyclassB class.
This new class can use the copy assignment operator from the TmyclassA as in the example below.
As you see, here, because of : public TmyclassA part, this TmyclassB class has trivial copy assignment operator from TmyclassA. Now we can use this in the copy of class objects as below.
Is there a full example of a trivial copy assignment operator in C++?
Here is an example with a copy assignment operator in a class.
here is the output”
As you see, in Modern C++, we can simply use the trivial copy assignment operator in other sub classes in C++ without any declaration.
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