C++中子类调用父类的有参构造函数

参考：

https://blog.youkuaiyun.com/qq_36846891/article/details/69666437 //java中子类构造与父类构造

https://blog.youkuaiyun.com/dan_lionly/article/details/52314869 //c++中子类构造与父类构造

#include <iostream>
using namespace std;
class A
{
  public:
  int a;
  int b;

  A()
  {
    cout<<"A Constructed\n";
  }
};

class B:A
{
  public:
  int c;
  int d;

  B()
  {
    cout<<"B Constructed\n";
  }

};

int main()
{

  B b;
  return 1;

}

如上面代码所示，B类继承自A类，当生成B的实例b时，要先执行A的构造函数，然后执行B的构造函数。结果如下所示:

若B使用有参构造函数，如下面代码所示，仍然会调用A的无参构造函数。

#include <iostream>

using namespace std;

class A
{
  public:
  int a;
  int b;

  A()
  {
    cout<<"A Constructed 1\n";
  }
  A(int a,int b)
  {
    this->a=a;
    this->b=b;
    cout<<"A Constructed 2\n";
  }

};

class B:A
{
  public:
  int c;
  int d;

  B()
  {
    cout<<"B Constructed 1\n";
  }

  B(int c,int d)
  {
    this->c=c;
    this->d=d;
    cout<<"B Constructed 2\n";
  }

};

int main()
{
  B b(1,1);
  return 1;
}

运行结果:

但是如何在构造函数中调用父类的有参构造函数呢？实现代码如下：

#include <iostream>
using namespace std;

class A
{
  public:
  int a;
  int b;
  A()
  {
    cout<<"A Constructed 1\n";
  }

  A(int a,int b)
  {
    this->a=a;
    this->b=b;
    cout<<"A Constructed 2\n";
    cout<<"this.a is "<<this->a<<" this.b is "<<this->b<<"\n";
  }

};

class B:A
{

  public:
  int c;
  int d;

  B()
  {
    cout<<"B Constructed 1\n";
  }

  B(int c,int d):A(100,200)
  {
    this->c=c;
    this->d=d;
    cout<<"B Constructed 2\n";
  }
};

int main()
{
  B b(1,1);
  cout<<"b.c is "<<b.c<<" b.d is "<<b.d <<"\n";
  return 1;
}

运行结果：

可以看见确实执行了有参构造函数，但是，调用的父类有参构造函数的参数是在子类的构造函数实现时便确定的。 

如果是linux环境，文件是.cpp，比如test.cpp，编译方式可以用gcc or g++

gcc test.cpp -lstdc++ -o test  or g++ test.cpp -o test，然后 ./test运行即可。