用戶定義的分隔符或分隔操作？

Question

我想用戶定義分隔符！但獲得像超載功能和一些更多的錯誤的錯誤！

string first_operator; 
string second_operator; 
std::cout << "Please enter the first seperation operator :"; 
getline(cin, first_operator, ' '); 

std::cout << "Please enter the second seperation operator :"; 
getline(cin, second_operator, ' '); 

string first_name; 
std::cout << "Please enter your name:"; 
getline(cin, first_name, first_operator); 

string last_name; 
getline(cin, last_name, second_operator); 

std::cout << first_name << " " << last_name << std::endl; 

std::cin.ignore(); 

Answer 1

沒有版本的std::getline()它接受一個std::string，或參照std::string，作爲其「分隔符」參數。

Considering only the version which takes a delimiter, the function std::getline() is declared as follows：

// Version 1a. 
template< class CharT, class Traits, class Allocator > 
std::basic_istream<CharT,Traits>& getline(std::basic_istream<CharT,Traits>& input, 
              std::basic_string<CharT,Traits,Allocator>& str, 
              CharT delim); 

// Version 1b (C++11 or later). 
template< class CharT, class Traits, class Allocator > 
std::basic_istream<CharT,Traits>& getline(std::basic_istream<CharT,Traits>&& input, 
              std::basic_string<CharT,Traits,Allocator>& str, 
              CharT delim); 

對於std::string，聲明是這樣的：

// Version 1a. 
std::istream& getline(std::istream& input, std::string& str, char delim); 

// Version 1b. 
std::istream& getline(std::istream&& input, std::string& str, char delim); 

注意，第三個參數是char。因此，您的分隔符必須是單個字符，而不是字符串。

---

考慮到這一點，如下我們可以重寫代碼：

char first_operator, second_operator; 
std::cout << "Please enter the first seperation operator :"; 
std::cin >> first_operator; // Get first character from input. 
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // Ignore the rest. 
std::cout << "Please enter the second seperation operator :"; 
std::cin >> second_operator; // Get first character from input. 
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // Ignore the rest. 

string first_name; 
std::cout << "Please enter your name:"; 
getline(cin, first_name, first_operator); 

string last_name; 
getline(cin, last_name, second_operator); 

std::cout << first_name << " " << last_name << std::endl; 

std::cin.ignore(); 

注意，這僅允許單字符分隔符。如果你想允許多字符分隔符，你需要做更復雜的處理。

std::string first_operator, second_operator; 
std::cout << "Please enter the first seperation operator :"; 
std::getline(std::cin, first_operator); 
std::cout << "Please enter the second seperation operator :"; 
std::getline(std::cin, second_operator); 

// Loop until name is entered correctly. 
bool done = false; 
do { 
    std::string name_buf; 
    std::cout << "Please enter your name:"; 
    std::getline(std::cin, name_buf); 

    auto first_op = name_buf.find(first_operator); 
    auto second_op = name_buf.find(second_operator); 
    if (first_op == std::string::npos || second_op == std::string::npos) { 
     std::cout << "Please separate your first and last names with the first specified operator, " 
        << "and follow your last name with the second specified operator.\n"; 
     continue; // Restart loop. 
    } 

    first_name = name_buf.substr(0, first_op); 
    auto last_start = first_op + first_operator.size(); 
    last_name = name_buf.substr(last_start, second_op - last_start); 
    done = true; 
} while(!done); 

看到它在行動here。忽略「請輸入x」這幾行的格式問題，這是由於Ideone如何處理示例代碼中的標準輸入引起的。

_{姓名取自xkcd。}