Detailed explanation of inheritance and dynamic memory allocation in C++
How does inheritance interact with dynamic memory allocation? For example, if the base class uses dynamic memory allocation and redefines the assignment and copy constructors, how will this affect the implementation of the derived class? The answer to this question depends on the attributes of the derived class. If the derived classes also use dynamic memory allocation, then you need to learn a few new tips. Let’s take a look at these two situations:
1. Derived classes do not use new
Do derived classes need to define destructors, copy constructors, and assignment operators for display?
unnecessary!
First, let's see if the destructor is needed. If the destructor is not defined, the compiler will define a default constructor that does not perform any operations. In fact, the default constructor of a derived class always requires some operations: after executing its own code, the base class destructor is called. Because we assume that members of the derived class do not need to perform any special operations, the default destructor is appropriate.
Let's look at the copy constructor. The default copy constructor performs member copying, which is not appropriate for dynamic memory allocation, but is appropriate for members of new derived classes. Therefore, only the inherited base class object needs to be considered. You should know that member replication will adopt the corresponding replication method according to the data type, so when copying a class member or inherited class component, it is done using the copy constructor of that class. Therefore, the default copy constructor of the derived class uses the display copy constructor of the base class to copy the base class member part of the derived class object. Therefore, the default copy constructor is suitable for new derived classes.
The same goes for assignment.
2. Use new for derived classes.
If the derived class requires a new operation, then it is necessary to display the destructor, copy constructor, and assignment operator.
The derived class destructor automatically calls the base class constructor, so its own responsibility is to clean up the execution of the derived class constructor.
Next, let’s look at the copy constructor:
DerivedClass::DerivedClass(const DerivedClass& de):BaseClass(de)
{
//.......
}
Look at the assignment operator:
DerivedClass::operator=(const DerivedClass& de)
{
if(this == &de) return *this;
BaseClass::operator=(de);
//..........
}
In short, when both base class and derived classes use dynamic memory allocation, the destructor, copy constructor and assignment operator of the derived class must use the base class method you want to use to process the base class elements. This requirement is met in three different ways.
1. For destructors, this is done automatically;
2. For constructors, this is done by calling the copy constructor of the base class in the initialized member list; if this is not done, the default constructor of the base class will be automatically called.
3. For the copy operator, this is done by calling the assignment operator of the base class displayed by the scope parsing operator.
The above is a detailed explanation of inheritance and dynamic memory allocation in C++. If you have any questions, please leave a message or go to the community of this site to communicate and discuss. Thank you for reading. I hope it can help you. Thank you for your support for this site!