problem with setting of file name

This is a discussion on problem with setting of file name within the C++ Programming forums, part of the General Programming Boards category; well here is my code... and i will bold what is being defined as an error. Code: void MCreateFile() { ...

  1. #1
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    problem with setting of file name

    well here is my code... and i will bold what is being defined as an error.
    Code:
    void MCreateFile()
    {
        ofstream File;
        ifstream testFile;
        string filename;
        
        CLEARSCREEN;
        
        cout<<"Please enter the filename: ";
        cin>>filename;
        if(testFile.open(filename.c_str()))
        {
           testFile.close();
           
           int samefile;
           
           cout<<"\nThere is a file at the current save location with the same name...";
           cout<<"\n  <1>Overwrite";
           cout<<"\n  <2>Rename Current File";
           cout<<"\n  <3>Quit";
           cout<<"\n  ->: ";
           cin>>samefile;
           switch(samefile)
           {
                           case 1:
                                testFile.open(filename.c_str(), ios::trunc);
                                testFile.close();
                                break;
                           case 2:
                                filename.clear();
                                cout<<"\nNew File Name: ";
                                cin>>filename;
                                break;
                           case 3:
                                Quit();
                                break;
                           default:
                                   cout<<"\nNot a valid entry!";
                                   cout<<"\n  ->: ";
           }
        }
                       
        if(!File.open(filename.c_str()));
        {
             cout<<"File could not be created!";
             Quit();
        }
    }
    here are my compiler errors....
    Code:
    73 C:\Dev-Cpp\My Stuff\C++\PhoneBook\PhoneBook4\definitions.h could not convert `(&testFile)->std::basic_ifstream<_CharT, _Traits>::open [with _CharT = char, _Traits = std::char_traits<char>]((&filename)->std::basic_string<_CharT, _Traits, _Alloc>::c_str [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](), (std::_Ios_Openmode)8u)' to `bool' 
    105 C:\Dev-Cpp\My Stuff\C++\PhoneBook\PhoneBook4\definitions.h could not convert `(&File)->std::basic_ofstream<_CharT, _Traits>::open [with _CharT = char, _Traits = std::char_traits<char>]((&filename)->std::basic_string<_CharT, _Traits, _Alloc>::c_str [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](), std::operator|((std::_Ios_Openmode)16u, (std::_Ios_Openmode)32u))' to `bool' 
    105 C:\Dev-Cpp\My Stuff\C++\PhoneBook\PhoneBook4\definitions.h in argument to unary !
    i realize that when you have a filename, it has to be a const char* type. whats goin on?

  2. #2
    Registered User whiteflags's Avatar
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    I'm not intirely clear on what open() returns right now, but you can use the function testFile.is_open() instead. Let the filestream try to open the file all the time.

  3. #3
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    open() returns a void, so it can't be used as part of a conditional expression

  4. #4
    Moderately Rabid Decrypt's Avatar
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    try
    Code:
    testfile.open(filename.cstr())
    if (!testfile.fail())
    instead.
    There is a difference between tedious and difficult.

  5. #5
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    ooo ok... that makes since...
    but that makes me run into another problem...
    is there a function i can use to test to see if the filename of the file that the user chooses is already in the current directory?
    like a overwrite or rename window?

  6. #6
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    In standard C++, you'll probably want to just open the file for reading, and if it fails to open, it doesn't exist. There are platform specific options, and there is also Boost::filesystem, if you want more control or a nicer interface.

  7. #7
    Registered User whiteflags's Avatar
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    It depends on the mode that you use open with. There are lots of them, and you can use them in combination if they're separated by a vertical bar.
    Code:
    ios::app append output 
    ios::ate  seek to EOF when opened 
    ios::binary open the file in binary mode 
    ios::in  open the file for reading 
    ios:: out  open the file for writing 
    ios::trunc  overwrite the existing file
    The default for ifstream is ios::in, so you don't have to really worry about overwriting. If you don't want to overwrite, just create a new file with a different name after the other one opens.
    Last edited by whiteflags; 05-11-2006 at 07:01 PM.

  8. #8
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    ok... i got rid of the compiler errors by taking the open function out of the conditionals...
    now i get bad logic....

    Code:
    /*********************/
    /**** MCreateFile ****/
    /*********************/
    void MCreateFile()
    {
        string filename;
        
        CLEARSCREEN;
        
        cout<<"Please enter the filename: ";
        cin>>filename;
        
        ifstream testFile(filename.c_str());
        
        if(testFile.is_open())
        {
           testFile.close();
           
           int samefile;
           
           cout<<"\nThere is a file at the current save location with the same name...";
           cout<<"\n  <1>Overwrite";
           cout<<"\n  <2>Rename Current File";
           cout<<"\n  <3>Quit";
           cout<<"\n  ->: ";
           cin>>samefile;
           switch(samefile)
           {
                           case 1:
                                testFile.open(filename.c_str(), ios::trunc);
                                testFile.close();
                                break;
                           case 2:
                                filename.clear();
                                cout<<"\nNew File Name: ";
                                cin>>filename;
                                break;
                           case 3:
                                Quit();
                                break;
                           default:
                                   cout<<"\nNot a valid entry!";
                                   cout<<"\n  ->: ";
           }
        }          
        ofstream File(filename.c_str());     
        if(!File);
        {
             cout<<"File could not be created!";
             Quit();
        }
    The bolded text is where the problem lies....
    I check to see if the file isnt created... and if it isnt ... it says what it says...
    And it even outputs that if i have if(File)
    it works for both true and false...
    whats goin on?

  9. #9
    Registered User whiteflags's Avatar
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    Code:
        ofstream File(filename.c_str());     
        if(!File);
        {
             cout<<"File could not be created!";
             Quit();
        }
    The semicolon is your problem, because now no matter what, the code block following it will execute.

  10. #10
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    hahaha... wow.... what a newbish mistake...ahhh its late... im tired... thats my excuse...
    thanks bro

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