尝试使用stringstream将字符串转换为int

Question

I'm trying check if a string representation equals given integer. I'm meant to use stringstream for this in a function. I also have an operator= for this as well.

I'm a little confused on how to execute these together and if I'm missing something. This is the last bit to an assignment I have, this is just a small snippet of my whole program. I can't find many guides on this, and I sense they all direct me to atoi or atod, which I'm not allowed to use.

#ifndef INTEGER
#define INTEGER
using std::string;
class Integer
{
private:
    int intOne;
    string strOne;
public:
    Integer() {
        intOne = 0;
    }
    Integer(int y) {
        intOne = y;
    }
    Integer(string x) {
        strOne = x;
    }
    void equals(string a);  
    Integer &operator=(const string*);
    string toString();
};

#endif 

In this header I'm not sure what argument I'm to use for the = operator.

#include <iostream>
#include <sstream>
#include <string>
#include "Integer.h"
using namespace std;

Integer &Integer::operator=(const string*)
{
    this->equals(strOne);
    return *this;
}

void Integer::equals(string a)
{
    strOne = a;
    toString(strOne);
}

string Integer::toString()
{
    stringstream ss;
    ss << intOne;
    return ss.str();
}



 #include <iostream>
#include <cstdlib>
#include <conio.h>
#include <string>
#include <ostream>
using namespace std;
#include "Menu.h"
#include "Integer.h"
#include "Double.h"



int main()
{
    Integer i1;
    i1.equals("33");
    cout << i1;
}

Sorry if its a bad question I'm not too familiar with this type of assignment and will take any help I can get. Thanks.

Answer 1

你可以使用std::to_strig() ，它允许你从int转换为代表相同数字的字符串。

Answer 2

So if i understand correctly, you want to overload operator = , and that is a bad idea, since operator= is used for assignment not for comparison.

The correct operator signature is:

ReturnType operator==(const TypeOne first, const TypeSecond second) [const] // if outside of class
ReturnType operator==(const TypeSecond second) [const] // if inside class

Since you can't compare string to integer (they are different types), you need to write your comparisment function, since you don't have one i will write one for you:

bool is_int_equal_string(std::string str, int i)
{
    std::string tmp;
    tmp << i;
    return tmp.str() == i;
}

Last but not least, you need to merge both of those, into one convenient operator:

// inside your Integer class
bool operator==(std::string value) const
{
    std::stringstream tmp;
    tmp << intOne;
    return tmp.str() == ref;
}

Now you can use this operator, just like any other:

Integer foo = 31;
if (foo == "31")
    cout << "Is equal" << endl;
else
    cout << "Is NOT equal" << endl;

I hope this helps.

Answer 3

If you are allowed to use std::to_string then it would be the best.

Otherwise, you could create a function to handle the equality between the string and the integer with the use of std::stringstream :

Example:

bool Integer::equal(const string& str)
{
    stringstream ss(str);
    int str_to_int = 0;
    ss >> str_to_int;

    if (intOne == str_to_int)
        return true;
    else
        return false;
}

Combine this with an if statement:

int main()
{
    Integer i{100};

    if (i.equal("100"))
        cout << "true" << endl;
    else
        cout << "false" << endl;
}