用户定义的分隔符或分隔操作？

Question

我想用户定义分隔符！但获得像超载功能和一些更多的错误的错误！

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

没有版本的std::getline()它接受一个std::string，或参照std::string，作为其“分隔符”参数。

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); 

对于std::string，声明是这样的：

// 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，第三个参数是char。因此，您的分隔符必须是单个字符，而不是字符串。

---

考虑到这一点，如下我们可以重写代码：

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，这仅允许单字符分隔符。如果你想允许多字符分隔符，你需要做更复杂的处理。

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); 

看到它在行动here。忽略“请输入x”这几行的格式问题，这是由于Ideone如何处理示例代码中的标准输入引起的。

_{姓名取自xkcd。}