Error: expected primary expression before '.' sign

Question

I am currently teaching C ++ using A C ++ for All-In-One dummies; second edition. To create this program, I use Qt. I understand that it is good practice to organize objects and classes in your header files and your prospective member functions in a .cpp file built in addition to main.cpp. In this regard, I am trying to start the exercises in this book as such, but only recently encountered the following error.

expected primary-expression before '.' token 

This error occurs on lines 31, 32, and 37, so they seem to relate to my class member functions.

My 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(); } 

I did some research to find that this error indicates a fairly wide range of syntax abuse. Unfortunately, I could not find an instance similar to mine; I was hoping to get some insights from some more experienced programmers. If this is a simple negligence problem at my end, I apologize in advance and appreciate the feedback. I’d better know if he gave me trouble, not a bit.

Since they include my member functions, I also included my header file and .cpp

controlingInput.cpp (I included my header file and iostream and sstream here, but for some reason the editor was asking me problems here)

 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 

And here is my control

 #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 

Thanks in advance for any feedback.

Answer 1

You are trying to call instance variables with the class itself, as if they were static (which would still be invalid syntax). For proper operation you will need an instance of ControlingInput .

 int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); ControlingInput ctrlInput; //Create instance ... string entered = ctrlInput.enterOnlyNumbers(); int num = ctrlInput.stringToANumber(entered); cout << endl << "You entered " << num << endl; // value is displayed ... string password = ctrlInput.EnterPassword(); cout << "shh... your password is " << password << endl; return a.exec(); }