C ++检查整个输入是否为浮点型

Question

So I'm trying to check my input for a valid input of 1 or 2. It works when I just enter a 3/4/5/6 or any character. But once I enter 1 or 2 anywhere in the input with some characters it skips straight through the check and continues on with the code.

So when I for example enter 1a, it chooses case 1 and keeps the a in the input buffer and messes up my code...

Also I want to run a check on other float-only inputs that can be about everything so I don't just want to check for 1 || 2

do
{
    while(!(cin >> iChoiceFile))
    {
        cout << "ERROR: Please enter 1 or 2: ";
        cin >> iChoiceFile;
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
    }

    switch(iChoiceFile)
    {
        case 1: makeNewFile();
            valid_answer = true;
            break;

        case 2: valid_answer = true;
            break;

        default: cout << "ERROR: Please enter 1 or 2: ";
            valid_answer = false;
            break;
    }

}while(!valid_answer);

Thanks in advance!

Answer 1

It looks like what you actually want is to check for an input for 1 or 2 as integers, not floats.

Try this instead:

#include <cctype>
#include <cstdlib>

//...

string choice;
cout << "Enter a character: ";
getline(cin,choice);
while(!isdigit(choice[0]) || (choice[0] != '1' && choice[0] != '2')){
    cout << "\nERROR! Please enter 1 or 2 only!" << endl;
    cout << "Enter a character: ";
    getline(cin,choice);
}
switch (atoi(&choice[0])){
    case 1: 
        makeNewFile();
        break;

    case 2:
        cout << "Functionality to execute when input is a 2" << endl;
        break;
}//no need for 'default'

Sample execution:

Enter a character: 5
ERROR! Please enter 1 or 2 only!
Enter a character: a
ERROR! Please enter 1 or 2 only!
Enter a character: This is an entire weird string
ERROR! Please enter 1 or 2 only!
Enter a character: 1s
makeNewFile();

We've successfully ignored all the characters after 1 in the last case.