C++ 带参数构造函数

我们知道，每当我们创建一个类时，会自动生成一个默认构造函数，在其他语言中，这个默认构造函数是隐藏的。但是当我们自己创建构造函数时，在主函数中创建对象时，我们可以自由地传递我们认为对构造函数来说是必要的参数。创建一个带参数的构造函数非常简单。我们只需要在类函数中添加必要的参数即可。

C++代码

// Here we are writing down the C++ Programming language code
// demonstrate the concept of Parameterized constructor in C++
#include 
using namespace std;
// the below code snippet helps us with creating the
// Parameterized constructor class in C++ language
class ParamA {
private:
// we have declared that variables b and c in private mode are
int b, c;
public:
ParamA (int b1, int c1)
{
    // we have declared that variables b and c in private mode are
    // given the values here as b1 and c1 now
b = b1;
c = c1;
}
// this is the getter to get the value for variable b when it is
// called
int getX ()
{
return b;
}
// this is the getter to get the value for variable c when it is
// called
int getY ()
{
return c;
}
};
// the main driver code functionality starts from here
int main ()
{
ParamA p1(10, 15);
cout << "the value we have created for p1.b is: " << p1. getX() << ", the value we have created for p1.b is: p1.c = " << p1.getY();
return 0;
}

输出：

/ tm p/ po Rl 42 Ph db .o
the value we have created for p1.b is: 10, the value we have created for p1.b is: p1.c = 15

C++代码

// Here we are writing down the C++ Programming language code
// demonstrate the concept of Parameterized constructor in C++
#include 
using namespace std;
// the below code snippet helps us with creating the
// Parameterized constructor class in C++ language
class ParamCode {
public:
int x;
ParamCode (int i);
~ParamCode ();
};
ParamCode::ParamCode (int i) {
x = i;
}
ParamCode::~ParamCode() {
cout<< "After destructing the objects which are having the value of x is as follows:  " << x <<" \n";
}
// the main driver code functionality starts from here
int main () {
ParamCode t1(20);
ParamCode t2(15);
cout<< "the values for t1.x is:  "<

输出：

/tmp/poRl42Phdb.o
the values for t1.x is:  20 the values for t2.x is:  15
After destructing the objects which have the value of x is as follows:  15
After destructing the objects which have the value of x is as follows:  20

C++代码

// Here we are writing down the C++ Programming language code
// demonstrate the concept of Parameterized constructor in C++

#include 

using namespace std;

// the below class we are creating to calculate the length of the rectangle 

class rectangle {

   private:

       double length;

       double breadth;

   public:

       // to demonstrate our concept, we are creating parameterised constructor to calculate the length of the rectangle
       rectangle(double len, double brt) {


// below code helps us with initialising the members of the private members of the class with certain variables 
                 length = len;

                 breadth = brt;

       }

       double calculateArea() {

                 return length * breadth;

       }

};

// the main driver code functionality starts from here

int main() {

       // below code snippet we have written in C++ programming language helps us with creating the objects
       // which are initialised with certain data members to make the object creation successful

       rectangle rect1(840, 18.6);

       rectangle rect2(628.5, 46);

       // the below couple of cout statements help us print the values after the operation is performed successfully!

       cout << "after calculating the area of rectangle 1 we have got as: " << rect1.calculateArea() << endl;

       cout << "after calculating the area of rectangle 2 we have got as: "<< rect2.calculateArea() << endl;

       return 0;

}

输出：

after calculating the area of rectangle 1, we have got as 15624
after estimating the size of rectangle two, we have obtained: 28911