C++ Primer 12章练习

12.2 StrBlob类的实现

class StrBlob
{
public:
	typedef vector<string>::size_type size_type;
	StrBlob():data(make_shared<vector<string>>()){}
	StrBlob(initializer_list<string> il) :data(make_shared<vector<string>>(il)) {}
	size_type size() const
	{
		return data->size();
	}
	bool empty() const
	{
		return data->empty();
	}
	void push_back(const string &t)
	{
		data->push_back(t);
	}
	void pop_back()
	{
		check(0, "pop_back on empty StrBlob");
		data->pop_back();
	}
	const string& front()
	{
		check(0, "front on empty StrBlob");
		return data->front();
	}
	const string& front() const
	{
		check(0, "front on empty StrBlob");
		return data->front();
	}
	const string& back()
	{
		check(0, "back on empty StrBlob");
		return data->back();
	}
	const string& back() const 
	{
		check(0, "back on empty StrBlob");
		return data->back();
	}
	
private:
	shared_ptr<vector<string>> data;
	void check(size_type i, const string &msg) const
	{
		if (i >= data->size())
			throw out_of_range(msg);
	}
};

12.6&&12.7 编写函数，返回一个动态分配的 int 的vector。将此vector 传递给另一个函数，这个函数读取标准输入，将读入的值保存在 vector 元素中。再将vector传递给另一个函数，打印读入的值。记得在恰当的时刻delete vector。

shared_ptr<vector<string>> alloc_vector()
{
	return make_shared<vector<string>>();
}

void assign_vector(shared_ptr<vector<string>> p)
{
	string i;
	while (cin >> i)
	{
		p->push_back(i);
	}
}
void print_vector(shared_ptr<vector<string>> p)
{
	for (auto it : *p)
	{
		cout << it << " ";
	}
	cout << endl;
	
}

int main()
{
	auto p = alloc_vector();
	assign_vector(p);
	print_vector(p);
	return 0;
}

12.14 connection函数

struct connection
{
	string ip;
	int port;
	connection(string ip_, int port_) :ip(ip_), port(port_) {}
};

struct destination
{
	string ip;
	int port;
	destination(string ip_, int port_): ip(ip_), port(port_) {}
};

connection connect(destination *pDest)
{
	shared_ptr<connection> pConn(new connection(pDest->ip, pDest->port));
	cout << "create connection " << pConn.use_count() << endl;
	return *pConn;
}

void disconnect(connection pConn)
{
	cout << "connection close" << pConn.ip << ": " << pConn.port << endl;
}

void end_connection(connection *pConn)
{
	disconnect(*pConn);
}

void f(destination &d)
{
	connection conn = connect(&d);
	shared_ptr<connection> p(&conn, end_connection);
	cout << "connection now " << p.use_count() << endl;
}
int main()
{	
	destination dest("202.118.176.67", 3316);
	f(dest);
	system("pause");
	return 0;
}

12.16 unique_ptr

int main()
{	
	unique_ptr<string> p1(new string("str"));
	unique<string> p2 = p1; //错误 unique_ptr不能拷贝与赋值 只能够直接初始化
	cout << *p1 << endl;
	system("pause");
	return 0;
}