C++对象初始化以及运算符重载

#include <iostream>
using namespace std;

class A{
private:
	int num;
public:
    A(int num){
		this->num = num;
	}
	
	void printA(){
		cout<<"A "<<num<<endl;
	}
};

template <class T>
class demostrate{
public:
	demostrate(T* pObj = 0){
		cout<<"default constructor"<<endl;
	};
	demostrate(const demostrate &demo){
		cout<<"copy constructor";
	}
	//demostrate(demostrate<T> demo){};
	demostrate& operator=(T *t);
};


template <class T>
demostrate<T>& demostrate<T>::operator=(T *t){
	cout<<"operator overload"<<endl;
	t->printA();
	return *this;
}

class B{
	
public:
	B(A* a){
		a->printA();
		cout<<"new A "<<endl;
	}
	
	B(int bint){
		cout<<"bint "<<bint<<endl;
	}
	
	B(int a, int b, int c){
		cout<<"output a,b,c "<<a<<b<<c<<endl;
	}
};

int main(){
	//第一种方法提示conversion from ‘A*’ to non-scalar type ‘demostrate<A>’ requested
	//带有声明的对象初始化，实际上是调用构造函数，所以构造函数一定要有demostrate(T* pObj = 0)形参列表
	demostrate<A> demo = new A(100);
	
	/*
	//第二种方法调用的是运算符重载方法
	demostrate<A> demo;
	demo = new A(100);
	
	
	B b= new A(200);
	
	B b2 = 300;
	
	B b3 = {100, 200, 300};
	*/
	return 0;
}

在C++中，为构造函数指定实参有三种等价形式：

       Account acct1("Anna Press");

       Account acct2 = Account("Anna Press");

       Account acct3 = "Anna Press";

       acct3的形式只能被用于指定单个实参的情形，对于两个以上的实参，只能使用acct1和acct2的形式，推荐acct1。