std::ifstream data type?

Question

The variable "read" in this program needs to be passed through a function and i don't know what data type it is. I have used http://www.cplusplus.com/reference/fstream/ifstream/ifstream/ and http://www.cplusplus.com/reference/fstream/ifstream/ but I'm struggling to find anything, is this just not possible?

int main()
{
string line = " ", ans = " ", ans2 = " ", data = " ";
int i = 0, j = 0;
cout << "What file do you want to read? : ";
cin >> ans;
cout << "What do you want the new file to be called? : ";
cin >> ans2;
ifstream read(ans.c_str());
for (i = 0; !read.eof(); i++)
{
    read_function(line, read);
    write_function(line, ans2);
}
return 0;
}


string read_function(string line, string read)
{
        getline(read, line, ' ');
        cout << line;
}

void write_function(string line, string ans2)
{
    ofstream write(ans2.c_str(), ios::app);
    write << line;
    write.close();
}

What do you mean by "struggling to find anything"? It literally says right there that the object `read` is of type `ifstream`, and you just linked to reference for _ifstream_. What is the problem? — Lightness Races in Orbit, Jul 05 '17 at 16:12
I need to pass the variable read through a function and i don't know what data type it is — ToastehMonkey, Jul 05 '17 at 16:12
It says right there. Is this a troll? @doctorlove no it doesn't — Lightness Races in Orbit, Jul 05 '17 at 16:12
`read` look slike a function definiton not a variable - is there more context to theis code and a specific error. — doctorlove, Jul 05 '17 at 16:13
@doctorlove {aka std::__cxx11::basic_string}' is not derived from 'std::basic_istream<_CharT, _Traits> — ToastehMonkey, Jul 05 '17 at 16:13
There's clearly some extra context to reproduce the error message - mention the rest of the code and the error in your question and we may be able to help — doctorlove, Jul 05 '17 at 16:14
That is not a [MCVE]. Still, it's enough to see that you're passing an `ifstream` to a function that expects a `string`. I don't know why you thought that would work. — Lightness Races in Orbit, Jul 05 '17 at 16:16
Furthermore, the loop condition `!read.eof()` is wrong. Which book are you using to learn C++? It's bad. — Lightness Races in Orbit, Jul 05 '17 at 16:18
Never heard of it; don't know why it's so highly rated on Amazon. Here's [our list](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). — Lightness Races in Orbit, Jul 05 '17 at 16:19
I have a working copy of this code where the for loop is inside the read function but my "boss" needs it to be in *int(main)* — ToastehMonkey, Jul 05 '17 at 16:20
`ifstream read(ans.c_str());` tells you that `read` is of type `ifstream`. What more do you need to know? — Angew is no longer proud of SO, Jul 05 '17 at 16:25
This code is for a company? Your boss accepts code like this? — Lightness Races in Orbit, Jul 05 '17 at 16:39

score 3 · Answer 1 · answered Jul 05 '17 at 16:24

3

You have ifstream read but a function

string read_function(string line, string read)
                                 // ^------

If you change the function to

 string read_function(string line, ifstream & read)
                                 // ^------

the read_function then expects a stream as the second parameter, not a string.

You will have a similar problem with the next function.

The comments point out other problems.

If you get an error about types, sit back and look at what you are passing to functions and what they expect.

answered Jul 05 '17 at 16:24

doctorlove

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Thank you so much, this is what i needed to know, Sorry to everyone else i am just starting to use c++ so my question might've seemed odd to you. :) – ToastehMonkey Jul 05 '17 at 16:27
Glad to have helped. Keep practising. Keep asking questions. Find one or two good books (look at the list in the comments). Ask you boss/work mates too. – doctorlove Jul 06 '17 at 11:25

std::ifstream data type?

1 Answers1