fstream: try catch and string input

[uj2n]

Hello!

I have just converted from Java and am trying to start learning by translating some of my old code. I want to write a FileHandler class that can read/write strings and objects to files. I am starting out with writing and reading text to/from a file.

#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

static string readFile() {
    ifstream myfile("example.txt");
    string returnString = "";
    if (myfile.is_open()) {
        string line;
        while (!myfile.eof()) {
            getline(myfile, line);
            returnString += line;
        }
        myfile.close();
        return returnString;

    } else {
        return NULL;
    }
}

int main(int argc, char** argv) {
    try {
        cout << readFile();
    } catch (exception e) {
        cout << "Failed reading file\n";
    }
    return (EXIT_SUCCESS);
}

Firstly, the try-catch:
In Java a function can be declared "throws exceptions", thus telling the compiler that when used, the function must be surrounded with try-catch. Is there anything similar in c++?
And is the use of catch(exception e) the same as catch(...)? (in Java catch(Exception e) catches every possible exception)

Secondly, input:
I want to open myFile using a string, but when doing this I can not compile my program!

what is the difference between:

ifstream myfile("example.txt");

and

string str = "example.txt";
ifstream myfile(str);

?

Thanks in advance!

[Bazzy]

In Java a function can be declared "throws exceptions", thus telling the compiler that when used, the function must be surrounded with try-catch. Is there anything similar in c++?

Yes but this feature is deprecated

And is the use of catch(exception e) the same as catch(...)? (in Java catch(Exception e) catches every possible exception)

In C++ you can throw any type, not only std::exception instances. catching a std::exception will catch only those, catching an ellipsis will catch everything

I want to open myFile using a string, but when doing this I can not compile my program!

on the current standard file streams constructors take C string arguments. To get a C string from a C++ string call str.c_str() ( this is going to be fixed with the next version of C++ )

[uj2n]

this feature is deprecated

Why? and how else should one do this?

and how is this done?static string readFile(const string url) throws exception{} is not compiled

catching an ellipsis will catch everything

Ok, thanks!

on the current standard file streams constructors take C string arguments
Ok, thanks!

[Bazzy]

Why?

because you can't know everything that may be thrown by the function called within your function.

and how else should one do this?

static string readFile(const string url) throw ( exception )
On some compiler it will have no effect. If you omit that means that the function can throw anything