c ++结构体构造函数_C ++中的构造函数

c ++结构体构造函数

Constructors in C++ or any other language are a member function of a class that is used to initialize the newly created objects.

C ++或任何其他语言的构造函数是用于初始化新创建的对象的类的成员函数。

They have the same name as that of the class and do not return any value.

它们具有与类相同的名称，并且不返回任何值 。

Working of Constructors:

施工人员的工作：

As soon as the compiler encounters a newly created object, it invokes the constructor of the corresponding class automatically.

编译器一旦遇到新创建的对象，就会自动调用相应类的构造函数。

Then, the constructor initializes the newly created object of the class.

然后，构造函数初始化该类的新创建的对象。

C ++中的构造函数类型 (Types of Constructors in C++)

Following are the types of Constructors in C++:

以下是C ++中构造函数的类型：

Default Constructors默认构造函数
Parameterized Constructors参数化构造函数
Copy Constructors复制 构造函数

1.默认构造函数 (1. Default Constructors)

Defaulter Constructors do not accept any arguments or parameters in it.

默认构造函数不接受任何自变量或参数。

This constructor is implicitly invoked by the compiler if not declared by the user explicitly.

如果用户未明确声明，则编译器将隐式调用此构造函数。

Syntax:

句法：


class_name()
{//code
}

Example:

例：


#include <iostream>
using namespace std; class Display {
public: int x; // Default Constructor Display() { x = 10;}
}; int main()
{ Display d; cout << "The value of x: " << d.x << endl ;return 1;
}

Output:

输出：


The value of x: 10

2.参数化构造函数 (2. Parameterized Constructors)

Parameterized constructors allowing the passing of parameters during the creation of an object.

参数化构造函数允许在对象创建期间传递参数。

It helps in the initialization of the objects and provides distinct values to the different data variables of the objects.

它有助于对象的初始化，并为对象的不同数据变量提供不同的值。

Syntax:

句法：


class_name(parameters)
{//code
}

Example:

例：


#include <iostream>
using namespace std;
class Multiply{
public://Parameterized constructorMultiply(int a, int b) {int result = a*b;cout<<result<<endl;}
};
int main(void){Multiply m(10, 10); //implicit call to the constructorMultiply ex = Multiply(100, 5); //explicit call to the constructorreturn 0;
}

Output:

输出：


100
500

3.复制构造函数 (3. Copy Constructors)

Copy Constructor creates a copy of an existing object of the corresponding class. Thus, it creates a copy of all the data variables of one object into another object.

Copy构造函数创建相应类的现有对象的副本。因此，它将创建一个对象的所有数据变量到另一个对象的副本。

Syntax:

句法：


class_name(const class_name & object_name)
{//code
}

Example:

例：


#include<iostream>
using namespace std;
class Construct
{int a, b;   public:Construct(int aa, int bb){a = aa;b = bb;}Construct (const Construct &con) // Copy constructor{ a = con.a;b = con.b;}void show (){cout<<a<<" "<<b<<endl;}
};int main()
{Construct C(5, 5);     Construct C1 = C;      // Calling the Copy constructorcout<<"Copy constructor:\n ";C1.show();return 0;
}

Output:

输出：


Copy constructor:5 5

C ++中的构造方法重载 (Constructor Overloading in C++)

Overloading serves with the same function definition having different numbers and types of arguments.

重载用于具有不同数量和参数类型的相同函数定义。

In a similar fashion of Function Overloading, even the Constructors can be overloaded in C++ language.

以类似的函数重载方式，即使构造函数也可以用C ++语言重载。

Example:

例：


#include<iostream>
using namespace std;
class Area_parameters
{public:int a, len, width;Area_parameters(int x){a = x;cout<<x<<endl;}Area_parameters(int l, int b){len = l;width = b;cout<<l<<" "<<b<<endl;}
};int main()
{Area_parameters obj(5);Area_parameters obj1(10, 20);}

Output:

输出：


5
10 20

构造函数与成员函数之间的区别 (Difference between Constructors and Member Functions)

Constructor doesn’t provide any return type, on the other hand, Functions do have a return type.构造函数不提供任何返回类型，另一方面，函数确实具有返回类型。
Constructor gets implicitly called when an object is created while Member functions need to be called explicitly.当需要显式调用成员函数时，在创建对象时隐式调用构造函数。

结论 (Conclusion)

Thus, in this article, we have understood the functionality served by the Constructors in C++.

因此，在本文中，我们了解了C ++中的构造函数所提供的功能。

参考资料 (References)

Constructors in C++ Documentation

C ++文档中的构造函数

翻译自: https://www.journaldev.com/35031/constructors-in-c-plus-plus

c ++结构体构造函数