Why won't getline function work multiple times in a for loop with an array of structures? [duplicate]

问题

I have a little problem. I've created a program that asks user to enter part's name and part's price for four diffrent parts. Each name and price fills a structure, and I have an array of four structures. When i do a for loop to fill all the names and prices, my getline functon doesn't work properly, it simply just skipps the entering part after I enter the first part's name. Can you please tell me why? Here's my code:

#include <iostream>
#include <string>

struct part {
    std::string name;
    double cost;
};

int main() {

    const int size = 4;

    part apart[size];

    for (int i = 0; i < size; i++) {
        std::cout << "Enter the name of part № " << i + 1 << ": ";
        getline(std::cin,apart[i].name);
        std::cout << "Enter the price of '" << apart[i].name << "': ";
        std::cin >> apart[i].cost;
    }
}

回答1:

std::getline consumes the newline character \n, whereas std::cin will consume the number you enter and stop.

To illustrate why this is a problem, consider the following input for the first two 'parts':

item 1\n
53.25\n
item 2\n
64.23\n

First, you call std::getline, which consumes the text: item 1\n. Then you call std::cin >> ..., which recognises the 53.25, parses it, consumes it, and stops. You then have:

\n
item 2\n
64.23\n

You then call std::getline for a second time. All it sees is a \n, which is recognised as the end of a line. Therefore, it sees a blank string, stores nothing in your std::string, consumes the \n, and stops.

To solve this, you need to make sure the newline is consumed when you store the floating-point value using std::cin >>.

Try this:

#include <iostream>
#include <string>
// required for std::numeric_limits
#include <limits>

struct part {
    std::string name;
    double cost;
};

int main() {

    const int size = 4;

    part apart[size];

    for (int i = 0; i < size; i++) {
        std::cout << "Enter the name of part № " << i + 1 << ": ";
        getline(std::cin,apart[i].name);
        std::cout << "Enter the price of '" << apart[i].name << "': ";
        std::cin >> apart[i].cost;

        // flushes all newline characters
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    }
}

来源：https://stackoverflow.com/questions/35104540/why-wont-getline-function-work-multiple-times-in-a-for-loop-with-an-array-of-st

标签

c++

arrays

string

for-loop

getline