类的构造函数类型一
使用this指针给类内参数赋值

class rlxy
{public:int a;rlxy(int a, int b, int c){this->a=a;this->b=b;this->c=c;cout << "rlxy" << endl;}protected:int b;private:int c;
};int main()
{rlxy ss(10, 20, 30);
}

类的构造函数类型二
使用参数列表给类内参数赋值

#include "iostream"using namespace std;class rlxy
{public:int a;rlxy(int a, int b, int c) : a(a), b(b), c(c){cout << a << endl;cout << b << endl;cout << c << endl;}protected:int b;private:int c;
};int main()
{rlxy ss(10, 20, 30);
}

类的构造函数类型三
类外写构造函数

#include "iostream"using namespace std;class rlxy
{public:int a;rlxy(int a, int b, int c);protected:int b;private:int c;
};rlxy::rlxy(int a, int b, int c)
{this->a = a;this->b = a;this->c = a;cout << a << endl;cout << b << endl;cout << c << endl;
}int main()
{rlxy ss(10, 20, 30);
}