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为什么我的文件 'database2' 是空的并且没有文件被重命名?在注释中说明问题的部分之后,文件“database2”变为 0 字节。文件“database2”也没有被重命名,文件“database”也没有被删除。请帮助我,这是我的代码的一部分:

int edit(){
    char KeyStroke;
    std::string strings;
    string name;
    string name1;
    std::string dummy;
    std::string strings2;
    std::string strings3;
    ifstream myfile;
    ofstream myfile1;
    bool found = false;

    myfile.open("database");
    cout << endl << "What is the name of the contact you wish to go in detail?" << endl;
    getline(cin, name);
    while ( !found && getline (myfile ,strings) ) {
        if (strings.find(name) != std::string::npos) {
            cout << endl << "Name:\t\t" << strings<<endl;
            std::getline( myfile, strings );
            cout << "Address:\t" << strings<<endl;
            std::getline( myfile, strings );
            cout << "Handphone:\t" << strings;
        }
    }

    start:
    cout << endl <<endl;
    cout << "What do you wish to edit?"<<endl;
    cout << "1) Name"<<endl;
    cout << "2) Address"<<endl;
    cout << "3) Handphone"<<endl;
    cout << "4) Nothing" << endl;
    myfile.close();


/*--Main part of this code is from here onwards--*/

    lol:
    myfile.open("database");
    myfile1.open("database2");
    KeyStroke = getch();
    switch(KeyStroke){
        case '1':
            cout << "What is the new name: ";
            getline(cin, name1);
            while ( !myfile.eof()) {
                getline (myfile ,strings);
                if (strings.find(name) != std::string::npos) {
                    myfile1 << name1 << endl;
                }
                else{
                    if(strings[0] == ' '){
                        continue;
                    }
                myfile1 << strings << endl;
                }
            }
        myfile1 << " ";
        myfile1.close();        /*Once the file closes here, the data written in earlier dissapears*/
        myfile.close();
        remove("database");
        pause1();
        rename("database2","database");
        goto start;
4

1 回答 1

3

这是正在发生的事情:

你有一个“循环”,带有“开始”标签和最后的 goto。所以这将是循环的第一部分:

    cout << endl <<endl;
    cout << "What do you wish to edit?"<<endl;
    cout << "1) Name"<<endl;
    cout << "2) Address"<<endl;
    cout << "3) Handphone"<<endl;
    cout << "4) Nothing" << endl;
    myfile.close();


/*--Main part of this code is from here onwards--*/

    lol:
    myfile.open("database");
    myfile1.open("database2");
    cin.get (&KeyStroke,256);

请参阅循环的第一部分,您打开/创建两个名为“database”和“database2”的文件(请注意,如果文件不存在,ofstream open 方法会创建该文件),然后等待用户输入。

假设用户按 1 来更改名称,在 case 1 语句的末尾你有这个:

        myfile1 << " ";
        myfile1.close();        /*Once the file closes here, the data written in earlier dissapears*/
        myfile.close();
        remove("database");
//      pause1(); // undefined
        rename("database2","database");
        goto start;

您关闭文件,删除数据库,并将 databese2 重命名为数据库,它按预期工作,然后使用 goto 返回“循环”的开头,这再次执行这部分代码:

cout << endl <<endl;
cout << "What do you wish to edit?"<<endl;
cout << "1) Name"<<endl;
cout << "2) Address"<<endl;
cout << "3) Handphone"<<endl;
cout << "4) Nothing" << endl;
myfile.close();

lol:
myfile.open("database");
myfile1.open("database2");

您打开数据库文件,因为您将旧的 database2 重命名为 database(database2 现在不存在),它会创建一个新的(当然是空的)。

希望能帮助到你。

于 2012-12-24T11:39:05.160 回答