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In C++, |
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The Here's a basic way to understand it:
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The Think of it like getting a box to store things in your house. The Using |
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The Imagine you have a remote control (the pointer) for a robot (the object). The robot has various functions, like walking or talking. In C++, if you want to use the remote to make the robot talk, you use |
Here's a code snippet example of using new
and delete
:
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int* ptr = new int; // Allocate memory for an integer using "new" *ptr = 42; // Assign a value to the memory location pointed by "ptr" cout << *ptr << endl; // Print the value pointed by "ptr" delete ptr; // Deallocate the memory using "delete" |
...
Finally, we use the delete
operator to deallocate the memory pointed by ptr
.
Here's an example of using ->
:
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#include <iostream> using namespace std; class MyClass { public: void printMessage() { cout << "Hello, world!" << endl; } }; int main() { // Allocate memory for a MyClass object using "new" MyClass* ptr = new MyClass; // Call the "printMessage" function using "->" ptr->printMessage(); // Deallocate the memory using "delete" delete ptr; return 0; } |
...
Class Declaration:
MyClass
is a simple class with one public member function namedprintMessage()
. This function, when called, will output "Hello, world!" to the console.Main Function:
main()
is the function where execution of the program starts.Dynamic Memory Allocation: Inside
main()
, a pointer toMyClass
(ptr
) is declared and allocated memory for an object ofMyClass
using thenew
operator. Thenew
operator returns a pointer to the beginning of the new block of memory.Calling Member Function through Pointer: The
printMessage()
function of theMyClass
object is then called using the arrow operator (->
). The arrow operator is used to access the member functions and member variables of an object through a pointer.Memory Deallocation: After the
printMessage()
function is called, the dynamically allocated memory is deallocated using thedelete
operator to prevent memory leaks. After this line,ptr
should not be used without first being reassigned, as it no longer points to a validMyClass
object.Return Statement: The
main()
function ends by returning0
, indicating successful execution of the program.
...
.
Demo:
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#include <iostream> #include <string> using namespace std; class Person { public: string name; int age; Person(const string& pString, int pint) : name(pString), age(pInt) {} void display() { cout << "Name: " << name << ", Age: " << age << endl; } }; int main() { // Using 'new' to dynamically allocate memory for a Person object Person *personPtr = new Person("John Doe", 30); // Using '->' to access members of the object pointed to by the pointer personPtr->display(); // Using 'delete' to deallocate the memory that was previously allocated with 'new' delete personPtr; return 0; } |
...
In the main
function, we allocate memory for a Person
object using the new
operator and assign the address of this memory to the personPtr
pointer. We then use the ->
operator to call the display
method of the Person
object pointed to by personPtr
. Finally, we use the delete
operator to free the memory that was allocated for the Person
object.Please note that using new
and delete
is generally avoided in modern C++, in favor of smart pointers and containers, which automatically manage memory.
Here's a detailed explanation of the different parts of the code:
Class Declaration:
Person
is a class with two public data members (name
of type string andage
of type int) and two public member functions. Thename
andage
represent the name and age of a person.Class Constructor:
Person
has a constructor that takes two arguments: a stringpString
for the person's name and an integerpInt
for the person's age. These parameters are used to initialize the data membersname
andage
respectively using an initializer list (: name(pString), age(pInt)
).Member Function: The
display
function is a member function that outputs the person's name and age to the console.Main Function:
main()
is the entry point where the execution of the program starts.Dynamic Memory Allocation: Inside
main()
, aPerson
pointerpersonPtr
is declared and memory is dynamically allocated for aPerson
object usingnew
. Thenew
operator returns a pointer to the block of memory allocated.Calling Member Function through Pointer: The
display()
function of thePerson
object is then invoked using the arrow operator (->
). The arrow operator is utilized to access member functions and member variables of an object via a pointer.Memory Deallocation: After calling
display()
, the dynamically allocated memory is deallocated usingdelete
to prevent a memory leak. After this line,personPtr
should not be used without being reassigned first, because it no longer points to a validPerson
object.Return Statement: The
main()
function ends by returning0
, signifying that the program executed successfully.
In summary, this This C++ code demonstrates the process of dynamically creating an object of a class, using it, and then cleaning it up to prevent memory leaks.