Outputing to a file

I know how to write basic stuff to a file but I'm having a problem.

In my main function a .txt file is opened up to write data to. The main function creates some objects that are output by using a print function.

Code:

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object.print();

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The problem that I'm having is that I can't figure out a way to write the data to the same file. The way the program is going to work is the file is always going to be the same name and I can't pass that name as a variable. So I tried just opening up that file in the object member function print's code and appending data to it but that did not work. What's a good way to go about doing this?

Could you please clarify? I don't see what exactly your goal is, why you can't achieve it, or what object.print() has to do with it.

I have a main function:

Code:

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ofstream csis;

int main(){

    csis.open("csis.dat");

    Do Stuff...

    cout << stuff; //outputs stuff to the terminal window
   
    csis << stuff; //writes the same stuff to the file

    Object fun;

    fun.dosomething(x,y);

    fun.print(); //this is where the problem comes in

    csis.close()
}

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The Object member function print looks like this:

Code:

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void Object::print(){

    cout << something; //outputs something to the terminal window;

    csis << something; //I want to somehow write this to the same file/append it to the file

}

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Instead of (or in addition to) a print() member function, overload operator<< for output streams. This may have to be a friend function.

Code:

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std::ostream& operator<<(std::ostream& out, const Object& rhs) {
    return out << rhs.something; // Or rhs.something(), then no need to be a friend function.
}

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With that done, you can easily write:

Code:

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cout << fun;
csis << fun;

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I'm already overloading the << operator for a different purpose so I don't think I can do it that way. Print and << are outputting different things.

Quote:

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I'm already overloading the << operator for a different purpose so I don't think I can do it that way. Print and << are outputting different things.

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Then just do it this way:

Code:

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void Object::print(std::ostream& out) {
    out << something;
}

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Out of curiosity, what are you doing with your current overloaded operator<< ?

overloaded operator << only outputs the string in my object.

print() outputs all variables in my object.

I still don't think that is going to fix my problem though :(. I'll try it but if it doesn't work I'll post up my code. I'm working on other parts of it. This outputting is important but I have more code to write before I can come back to this. I'll post up my code after I'm done coding the rest.

Quote:

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Originally Posted by warfang

overloaded operator << only outputs the string in my object.

print() outputs all variables in my object.

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FWIW, I'm not really a C++ guy, but I find that counterintuitive. If I used operator<<, I would expect it to output the whole object since it is "acting" on the whole object.

A special printing function that only does a subset of the class to me it would seem to be the job of a special printing function such as printstring.

[edit]And would you want this function to receive a stream reference such that you could specify an fstream or iostream?

Go ahead and tell my teacher that one. I wish we had that much freedom in his labs... It would make them a lot less confusing.

If the problem is in the guts of the implementation of this function, it would be wise to post the guts of the implementation. A minimal compilable snippet of code that demonstrates the issue(s) is generally the fastest way to a solution.

EDIT: Look at my last post with the code...

Em. Didja know you can attach files to posts? Or even zip a project and post the zip?

Anyway, without "strdrv.h" -- unless I messed it, which happens all too frequently -- I can't try to build what you have.

Wow, no I didn't know you could add a files to posts. Well I'll try it now :D.

Well it didn't let me add a zip so in the file name I added .txt. So it's String.zip.txt. All you'll have to do is take out the .txt from the filename and you should be able to unzip it. thanks.

EDIT: The derived files are "case.cpp" and "reverse.cpp". The base file is "string.cpp" and the driver file "strdrv.cpp".

Note: You'll have to comment out test21 because I'm having trouble with a function.

Rest of the files.

Quote:

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Originally Posted by warfang

Wow, no I didn't know you could add a files to posts. Well I'll try it now :D.

Well it didn't let me add a zip so in the file name I added .txt. So it's String.zip.txt. All you'll have to do is take out the .txt from the filename and you should be able to unzip it.

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My bad. At one time I thought .zip's we're okay.

My time is limited, but I think you've posted enough for a thorough run-through by those that follow. Or else you'll hear otherwise. :)

Ehhh I'm having issues with my inherited classes so I'll just comment it all out.

Ok, thanks for your help up until this point. I'm getting really worried now. My countless hours of programming are summing up to nothing at this point if I can't figure out these last two things (inheritance problem and writing to the file) :'(.

Update: I have fixed everything in my program (YEAH SO HAPPY) except for this writing to a file. I'm reading a book on C++ and searching online but I haven't been able to find anything that helps yet. If you could that would be awesome!