C++ cin 对象

❮ iostream 对象

int x; 
cout << "Type a number: "; // Type a number and press enter
cin >> x; // Get user input from the keyboard
cout << "Your number is: " << x; // Display the input value 

定义和用法

The cin object is used to read keyboard input or data from a file. (cin 对象用于读取键盘输入或文件数据。)

The most common way to use cin is with the >> extraction operator. The extraction operator converts input data to the appropriate type for the variable (最常用的使用 cin 的方法是使用 >> 提取运算符。提取运算符将输入数据转换为变量的适当类型)

int x;
cin >> x;

The extraction operator can be used more than once on the same line to put data into multiple variables (提取运算符可以在同一行上多次使用，将数据放入多个变量中)

int x, y;
cin >> x >> y;

Note: The cin object is defined in the <iostream> header file. (注意： cin 对象定义在 <iostream> 头文件中。)

方法

In addition to the >> extraction operator, the cin object also has methods to read input. (除了 >> 提取运算符外，cin 对象还有用于读取输入的方法。)

get()

The cin.get() method reads one character from the input source and returns it. ( cin.get() 方法从输入源读取一个字符并返回它。)

char c = cin.get();
cout << c;

The cin.get(str, n) method writes up to n characters into the char array str which are copied from the input source. If a new line character \n is found it stops at the new line without including it. The last written character is always a null terminating character \0. ( cin.get(str, n) 方法将从输入源复制的最多 n 个字符写入 char 数组 str 中。如果找到换行符 \n，它会在不包含换行符的情况下停止。最后一个写入的字符始终是一个空终止字符 \0。)

An extra parameter can be used to specify a different character than \n as a delimiter. (可以使用额外参数指定一个不同于 \n 的字符作为分隔符。)

char str[20];
cin.get(str, 5);
cout << c;

// Stop reading when a "." is found
cin.get(str, 5, '.');
cout << c;

getline()

The cin.getline(str, n) method is the same as get(str, n) except that when the new line character \n or specified delimiter is found, it is discarded from the input source so that the next cin operation won't use it. ( cin.getline(str, n) 方法与 get(str, n) 相同，不同之处在于，当找到换行符 \n 或指定的分隔符时，它会被从输入源中丢弃，以便下一次 cin 操作不会使用它。)

char str[20];
cin.getline(str, 5);
cout << c;

// Stop reading when a "." is found
cin.getline(str, 5, '.');
cout << c;

read()

The cin.read(str, n) method reads up to n characters from the input source and writes them into the char array str without checking for delimiters and without adding a null terminating character \0. ( cin.read(str, n) 方法从输入源读取最多 n 个字符，并将它们写入 char 数组 str 中，而不检查分隔符，也不添加空终止字符 \0。)

char str[] = "Hello World";
cin.read(str, 5);
cout << str;

gcount()

The cin.gcount() method returns the number of characters that were used from the input souce by one of the above methods. ( cin.gcount() 方法返回上述方法中使用的来自输入源的字符数。)

char str[20];
cin.get(str, 5);
int num = cin.gcount();
cout << "Read " << num << " characters and got " << str << "\n";

❮ iostream 对象