我目前正在使用 A C++ for Dummies All-In-One 自学 C++；第二版。要创建这个程序，我正在使用 Qt。我理解在你的头文件中组织对象和类是一个很好的做法，并在一个除了 main.cpp 之外构建的 .cpp 文件中预期你的成员函数。在这方面，我尝试运行本书中的练习，但最近遇到了以下错误。
expected primary-expression before '.' token
此错误发生在第 31、32 和 37 行，因此它们似乎与我的类成员函数特别相关。
我的 main.cpp
#include "controlinginput.h"
#include <QtCore/QCoreApplication>
#include <iostream>
#include <sstream>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
// just a basic name-entering
string name;
cout << "What is your name?";
cin >> name;
cout << "Hello " << name << endl;
/* now you are asked for a number
but the computer will allow you to enter anything*/
int x;
cout << endl << "Enter a number! Any Number!" << endl;
cin >> x;
cout << "You choose " << x << endl;
/* now youll be asked for a number again
but the computer will only allow numbers */
cout << endl<< "This time you will ONLY be able to enter a number! " << endl;
cout << "SO, Pick a number! any number!" << endl;
string entered = ControlingInput.enterOnlyNumbers(); // ###Error###
int num = ControlingInput.stringToANumber(entered); // ###Error###
cout << endl << "You entered " << num << endl; // value is displayed
//Now finally we enter the password
cout << endl;
cout << "Please enter a password" << endl;
string password = ControlingInput.EnterPassword(); // ###Error###
cout << "shh... your password is " << password << endl;
return a.exec();
}
我做了一些研究，发现这个错误表明存在相当广泛的语法误用。不幸的是，我找不到与我的特别相似的实例；我希望从一些更有经验的程序员那里得到一些见解。如果这是一个由于我的疏忽而导致的简单问题，我提前道歉并感谢您的反馈。如果它给我带来很多麻烦而不是一点点，我会学得更好。
因为这些包括我的成员函数，所以我还包括了我的头文件和 .cpp
controlingInput.cpp （我已经包含了我的头文件和iostream这里sstream但是由于某种原因编辑器在这里给了我问题）
using namespace std;
ControlingInput::ControlingInput()
{
}
int ControlingInput::stringToANumber(string MyString)
{
istringstream converter(MyString); //Holds the string that was passed to this function
int result; //Holds the integer result
//perform the conversion
converter >> result;
return result; //function completes and returns converted string
}
string ControlingInput::enterOnlyNumbers()
{
string numbAsString = ""; // this holds our numeric string
char ch = getch(); // This gets a single character from our user
//Says to keep gettting characters from our user untill user presses enter
while (ch != '\r') // \r is the enter key
{
//This says to add characters only if they are numbers
if (ch >= '0' && ch <='9')
{
cout << ch; // show
numbAsString += ch; // add character to the string
}
ch = getch(); // get the next character from the user
}
return numbAsString;
}
string ControlingInput::EnterPassword()
{
string numbAsString = ""; //this will hold our password string
char ch = getch(); // this gets a single char from our users just like before
//keep gettting characters from the user until enter/return is pressed
while (ch != '\r'); // \r is the enter or return key
{
//for security passwords are displayed as asterisks instead of characters
cout << '*';
//add character input into the password string
numbAsString += ch;
//Get the next character from the user
ch = getch();
}
return numbAsString; // return the user input from this function
这是我的 controlingInput.h
#ifndef CONTROLINGINPUT_H
#define CONTROLINGINPUT_H
#include <iostream>
using namespace std;
class ControlingInput
{
public:
int stringToANumber(string MyString);
string EnterPassword();
string enterOnlyNumbers();
};
#endif // CONTROLINGINPUT_H
提前感谢您的任何反馈。