是否可以在从两个类中读取成员变量的文件时编写提取运算符?第一类是CPerson,其中包含姓名和EGN(社会安全号码),第二类是CStudent,其中包含FN(教师编号)和包含各种测试的地图(测试代码和获得积分)。目前我已经为CStudent类重载了一个提取运算符,这意味着我可以访问其私有成员,但我想为CPerson做同样的事情,所以我不需要为该类使用setter函数同样。
class CPerson
{
private:
string name;
string EGN;
public:
CPerson(const string n, const string e)
{
name=n;
EGN=e;
}
void setname(const string n) {name=n;}
void setEGN(const string e) {EGN=e;}
};
class CStudent: public CPerson
{
private:
string FN;
map<int, int> st_tests;
public:
CStudent(const string o, const string p, const string n):CPerson(o,p)
{FN=n;}
friend istream &operator>> (istream &, CStudent &);
};
istream &operator>> (istream &input, CStudent &c)
{
string z, x, y, line;
int d, e;
getline(input,line);
istringstream ln(line);
ln >> z >> x >> c.FN;
c.setname(z);
c.setEGN(x);
while(true)
{
ln >> d >> e;
c.st_tests[d] = e;
if(!ln.good())
break;
}
return input;
}
class CGroup
{
private:
string spec; //specialty
int kurs; //course
int grupa; //group
vector<CStudent> students; //vector of CStudent objects
public:
CGroup(const string filename) //constructor with name of file to be read as parameter
{
string a;
int b, c;
ifstream st;
st.open(filename.c_str(),ios::in);
if(!st)
{
cout<<"Cannot open "<<filename<<" or file does not exist."<<endl;
exit(1);
}
string line;
getline(st,line);
istringstream group(line);
group >> a >> b >> c;
spec = a;
kurs = b;
grupa = c;
while(!st.eof())
{
CStudent student;
st >> student;
students.push_back(student);
}
st.close();
}
};
如果需要,以下是其中一个文件中的内容:
KST 1 1
Ivan 9404019382 61360125 1 55 2 90 3 78 12 82 13 99 14 78 15 72
Kaloqn 9311281029 61360126 1 82 2 43 3 95 13 50
Airqn 9408132918 61360127 1 91 2 40 3 89
Mariq 9409071824 61360128 1 55 2 91 3 78 16 0
Ginka 9312198212 61360129 1 87 2 84 3 15
Leika 9405221982 61360130 1 25 2 76 3 56
Shumaher 9305119225 61360131 1 94 2 75 3 92
Onzi 9408108876 61360132 1 40 2 59 3 49
更新了运营商:
CPerson
{
friend istream &operator>> (istream &, CPerson &);
};
istream &operator>> (istream &input, CPerson &c)
{
input >> c.name >> c.EGN;
return input;
}
istream &operator>> (istream &input, CStudent &c)
{
int d, e;
string line;
getline(input,line);
istringstream ln(line);
ln >> static_cast<CPerson&>(c) >> c.FN;
while(ln >> d >> e)
c.st_tests[d] = e;
return input;
}
结果:
Ivan 9404019382 61360125 1 55 2 90 3 78 12 82 13 99 14 78 15 72
Kaloqn 9311281029 61360126 1 82 2 43 3 95 12 82 13 50 14 78 15 72
Airqn 9408132918 61360127 1 91 2 40 3 89 12 82 13 99 14 78 15 72
Mariq 9409071824 61360128 1 55 2 91 3 78 12 82 13 99 14 78 15 72 16 0
Ginka 9312198212 61360129 1 87 2 84 3 15 12 82 13 99 14 78 15 72 16 0
Leika 9405221982 61360130 1 25 2 76 3 56 12 82 13 99 14 78 15 72 16 0
Shumaher 9305119225 61360131 1 94 2 75 3 92 12 82 13 99 14 78 15 72 16 0
Onzi 9408108876 61360132 1 40 2 59 3 49 12 82 13 99 14 78 15 72 16 0
答案 0 :(得分:0)
您可以在name
中阅读EGN
和CPerson
:
istream &operator>> (istream &input, CPerson &c)
{
// this is friend function, so you can access private members of CPerson
input >> c.name >> c.EGN; // or something similar...
return input;
}
提取到CStudent
会先将数据提取到CPerson
(名称和EGN应该是输入数据中的第一个字符串):
istream &operator>> (istream &input, CStudent &c)
{
input >> static_cast<CPerson&>(c); // read CPerson's data first
string line;
if(getline(input, line))
{
istringstream iss(line);
while(iss >> d >> e) // then read CStudent's special data
c.st_tests[d] = e;
}
return input;
}
一些建议的改进:
CStudent student; // you will need default constructor for this
while(st >> student)
students.push_back(student); // read like this in CGroup
std::string
传递const&
。在没有参考的情况下,使用这些参数中的const
限制自己几乎没有用。
CGroup(string const& filename);
CPerson(string const& n, string const& e)