errore ofstream

Question

Questo è in riferimento a un'altra domanda che ho posto, sebbene sia interamente una sua domanda.

quando compilo ottengo due errori:

1 >. \ asst4.cpp (73): errore C2065: 'outfile': identificatore non dichiarato

1 >. \ asst4.cpp (73): errore C2228: a sinistra di '.close' deve essere class / struct / union

Sono leggermente confuso su ciò che ho fatto in modo errato qui? Raccomandazioni o idee? (Il file effettivo si trova nella parte superiore del codice.

Ecco il codice completo:

#include<iostream>
#include<fstream>  //used for reading/writing to files.
#include<string>    //needed for the filename.
#include<stdio.h>   //for goto statement

using namespace std;

int main()
{
    string start;
    char choice;
    char letter;
    int x;
    int y;
    int z;
    string filename;
    int garbage = rand()%('!' - '~' + 1 );
    cout << "Would you like to encrypt or decrypt a file? Please type enc, dec, or stop (case sensitive): " ;
    cin >> start;
    while(start == "enc")
    {
        x = 1;
        y = 1;
        cout << "How many garbage characters would you like between each correct character?: " ;
        cin >> z;
        cout << endl << "Please insert the name of the document you wish to encrypt, make sure you enter the name, and the file type (ie: filename.txt): " ;
        cin >> filename;
        ifstream infile(filename.c_str());
        while(!infile.eof())
        {
            ofstream outfile("encrypted.txt", ios::out);
            infile.get(letter); 
            if (x == y)         
                {
                outfile << garbage;
                x++;             
            }
            else
            {
                if((x - y) == z)            
                {
                    outfile << letter;          
                    y = x;                  
                }
                else                        
                {                           
                    outfile << garbage;
                    x++;
                }
            }
        }
        cout << endl << "Encryption complete...please return to directory of program, a new file named encrypted.txt will be there." << endl;
        infile.close();
        outfile.close();
        cout << "Do you wish to try again? Please press y then enter if yes (case sensitive).";
        cin >> choice;
        if(choice == 'y')
        {
            start = "enc";
        }
        else
        {
            cout << endl << "Do you wish to decrypt a file? Please press y then enter if yes (case sensitive).";
            if(choice = 'y')
            {
                start == "dec";
            }
            else
            {
                start == "no";
            }
        }
    }
    while(start == "dec")
    {

      //lets user choose whether to do another document or not.
      //used to track each character in the document.
        x = 1;    //first counter for tracking correct letter.
        y = 1;    //second counter (1 is used instead of 0 for ease of reading, 1 being the "first character").
              //third counter (used as a check to see if the first two counters are equal).
        //allows for user to input the filename they wish to use.
        cout << "Please make sure the document is in the same file as the program, thank you!" << endl << "Please input document name: " ;
        cin >> filename; //getline(cin, filename);  
        cout << endl;
        cout << "'Every nth character is good', what number is n?: ";
        cin >> z;   //user inputs the number at which the character is good. IE: every 5th character is good, they would input 5.
        cout << endl;
        z = z - 1;  //by subtracting 1, you now have the number of characters you will be skipping, the one after those is the letter you want.
        ifstream infile(filename.c_str()); //gets the filename provided, see below for incorrect input.
        if(infile.is_open()) //checks to see if the file is opened.
        {
            while(!infile.eof())    //continues looping until the end of the file.
            {   
                    infile.get(letter);  //gets the letters in the order that that they are in the file.
                    if (x == y)          //checks to see if the counters match...
                    {
                        x++;             //...if they do, adds 1 to the x counter.
                    }
                    else
                    {
                        if((x - y) == z)            //for every nth character that is good, x - y = nth - 1.
                        {
                            cout << letter;         //...if they don't, that means that character is one you want, so it prints that character.
                            y = x;                  //sets both counters equal to restart the process of counting.
                        }
                        else                        //only used when more than every other letter is garbage, continues adding 1 to the first
                        {                           //counter until the first and second counters are equal.
                            x++;
                        }
                    }
            }
            cout << endl << "Decryption complete...please return to directory of program, a new file named encrypted.txt will be there." << endl;
            infile.close();
            cout << "Do you wish to try again? Please press y then enter if yes (case sensitive).";
            cin >> choice;
            if(choice == 'y')
            {
                start == "dec";
            }
            else
                {
                cout << endl << "Do you wish to encrypt a file? Please press y then enter if yes (case sensitive).";
                if(choice == 'y')
                {
                    start == "enc";
                }
                else
                {
                    start == "no";
                }
            }
        }
        else  //this prints out and program is skipped in case an incorrect file name is used.
        {
            cout << "Unable to open file, please make sure the filename is correct and that you typed in the extension" << endl;
            cout << "IE:" << "     filename.txt" << endl;
            cout << "You input: " << filename << endl;
            cout << "Do you wish to try again? Please press y then enter if yes (case senstive)." ;
            cin >> choice;
            if(choice == 'y')
            {
                start == "dec";
            }
            else
            {
                start == "no";
            }
        }
        getchar();  //because I use visual C++ express.
    }
}

Grazie in anticipo! Jeff

Answer 1

Problema di scoping. Stai dichiarando outfile nel tuo ciclo while, ma stai provando ad accedervi al di fuori di detto ciclo while.

Sposta ofstream outfile (" ;crypted.txt " ;, ios :: out); sulla riga subito dopo il tuo ifstream infile (nomefile.c_str ()); che è prima del tuo while (! infile.eof ()) .

Answer 2

Hai due possibilità: come menzionato X-istence, il motivo per cui la tua chiamata a outfile.close () non è stata compilata è perché l'oggetto 'outfile' non esiste nello stesso ambito della dichiarazione di outfile.

Puoi spostare la linea

ofstream outfile("encrypted.txt", ios::out);

al di fuori del ciclo while in modo che rispetti le stesse regole di scoping di infile, oppure puoi spostare la tua chiamata su outfile.close (); all'interno del ciclo while, che lo sposterebbe nell'ambito corrente in cui esiste il file di output.

La mia preferenza sarebbe quella di spostare la dichiarazione di outfile al di fuori del ciclo while in quanto l'apertura di un file è un'operazione piuttosto costosa e non vuoi davvero farlo per ogni lettera che leggi dall'infile. Aprilo una volta, chiudilo una volta è la strada da percorrere in questo caso.