How can I fix this error? "Method 'str' could not be resolved"

Question

What is the meaning of this problem and how can I fix it?
It's look like it's not meet the function str() while I try to use it.
In fact, I want to take the "string" from rhs and to put it in this->file, so if you have alternative idea, it's good too.

Method 'str' could not be resolved
Method 'c_str' could not be resolved

#include <cstdio>
#include <iostream>
#include <sstream>

class MyFile {
    FILE* file;
    MyFile& operator=(const MyFile& rhs) const;
    MyFile(const MyFile& rhs);
public:
    MyFile(const char* filename) :
            file(fopen(filename, "w")) {
        if (file == NULL) {
            throw std::exception();
        }
    }
    ~MyFile() {
        fclose(file);
    }

    template<typename T>
    MyFile& operator<<(const T& rhs) {
        std::ostringstream ss;
        ss << rhs;
        if (std::fputs(ss.str().c_str(), this->file) == EOF) { // Method 'str' could not be resolved
            throw std::exception();
        }
        return *this;
    }
};

Resolving `str()` works fine in https://godbolt.org/g/8KKrgh (after fixing the mistyped class name), but `std::fputs` expects a `char*`, not a `string`. — Christopher Creutzig, Jun 04 '18 at 07:10
Possible duplicate of [How to write user input to a text file using fputs in C++](https://stackoverflow.com/questions/5546725/how-to-write-user-input-to-a-text-file-using-fputs-in-c) — , Jun 04 '18 at 07:18
@NickyC I tried it : `if (std::fputs(ss.str().c_str(), this->file) == EOF)` and it's not working yet.. — AskMath, Jun 04 '18 at 07:21
What is the error after you change to `if (std::fputs(ss.str().c_str(), this->file) == EOF)`? — zhm, Jun 04 '18 at 07:23
What compiler are you using? I test with visual studio and MingGW, both work after change to `if (std::fputs(ss.str().c_str(), this->file) == EOF)`. — zhm, Jun 04 '18 at 07:25

score 3 · Accepted Answer · answered Jun 04 '18 at 07:21

3

Are you sure that str() is the function that cannot be resolved? Instead, I assume fputs() cannot be resolved. The reason is that fputs expects a const char*, but you are giving it an std::string which is returned by str(). Try fputs(ss.str().c_str(), this->file).

answered Jun 04 '18 at 07:21

sebrockm

5,733
2
16
39

Your updated code compiles just fine with gcc. Every standard-compliant compiler should be able to compile it... – sebrockm Jun 04 '18 at 07:52

Kartik Maheshwari · Answer 2 · 2018-06-04T07:25:02.433

0

    std::ostringstream oss;
    FILE *file;
    std::string s = oss.str();
    std::cout << s << '\n';
    std::fputs(s.c_str(), file);

covert ostringstream to std::string and than convert in const char *

edited Jun 04 '18 at 07:25

answered Jun 04 '18 at 07:23

Kartik Maheshwari

357
2
11

How can I fix this error? "Method 'str' could not be resolved"

2 Answers2