这是一个有关于C++的问题，作业中遇到的问题，求助！

Question

read one string from the file called "infile.txt" into your string class using your read member function（）
The class will store the string in dynamic memory that is pointed to with the pointer. When you first create an MYString object you should allocate 20 spaces of memory (using the new command). The string will be stored as a cstring in this memory.
我需要用到这个函数 read( istream & istr) : bool ，并且要在.cpp文件中实现，请问我应怎样完成这个操作？

Answer 1

class MYString
{
private:
char *_data;
public:
MYString()
{
_data = new char[20];
}

    void read()
    {
        // read from infile.txt
    }

};

作业的要求是这样吧好像是。