c ++ 函數的esp指針

Create a class along with data member and member functions and then access the member functions by using a pointer in C++.

創建一個類以及數據成員和成員函數，然后使用C ++中的指針訪問成員函數。

如何通過指針訪問成員函數？ (How to access a member function by pointer?)

To access a member function by pointer, we have to declare a pointer to the object and initialize it (by creating the memory at runtime, yes! We can use new keyboard for this).

要通過指針訪問成員函數 ，我們必須聲明一個指向該對象的指針并將其初始化(通過在運行時創建內存，是的！我們可以為此使用新鍵盤)。

The second step, use arrow operator -> to access the member function using the pointer to the object.

第二步，使用箭頭運算符->使用指向對象的指針訪問成員函數。

Syntax:

句法：

//pointer to object declaration
class_name *pointe_name;
//memory initialization at runtime 
pointer_name = new class_name;
//accessing member function by using arrow operator
pointer_name->member_function();

Example:

例：

In the below example - there is a class named Number with private data member num and public member functions inputNumber(), displayNumber().

在下面的示例中-有一個名為Number的類，具有私有數據成員num和公共成員函數inputNumber()和displayNumber() 。

In the example, we are creating simple object N and a pointer to the object ptrN and accessing the member functions by using simple object N and the pointer to the object ptrN.

在該示例中，我們將創建簡單對象N和指向對象ptrN的指針，并通過使用簡單對象N和指向對象ptrN的指針來訪問成員函數。

Program:

程序：

#include <iostream>
using namespace std;
class Number
{
private:
int num;
public:
//constructor
Number(){ num=0; };
//member function to get input
void inputNumber (void)
{
cout<<"Enter an integer number: ";
cin>>num;
}
//member function to display number 
void displayNumber()
{
cout<<"Num: "<<num<<endl;
}
};
//Main function
int main()
{
//declaring object to the class number
Number N;
//input and display number using norn object
N.inputNumber();
N.displayNumber();
//declaring pointer to the object 
Number *ptrN;
ptrN = new Number; //creating & assigning memory 
//printing default value
cout<<"Default value... "<<endl;
//calling member function with pointer 
ptrN->displayNumber();
//input values and print 
ptrN->inputNumber();
ptrN->displayNumber();
return 0;
}

Output

輸出量

Enter an integer number: 10
Num: 10
Default value...
Num: 0
Enter an integer number: 20
Num: 20

Explanation:

說明：

The main three steps needs to be understood those are:

需要理解的主要三個步驟是：

1. Pointer to object creation: Number *ptrN;

   指向對象創建的指針： Number * ptrN;

2. Dynamic memory initialization to the pointer object: ptrN = new Number;

   指針對象的動態內存初始化： ptrN = new Number;

3. Accessing member function by using "Arrow Operator": ptrN->displayNumber();

   通過使用“箭頭運算符”訪問成員函數： ptrN-> displayNumber();

翻譯自: https://www.includehelp.com/cpp-programs/accessing-member-function-by-pointer.aspx

c ++ 函數的esp指針