C++ Primer Plus 学习笔记 第十六章 string类

string类的构造函数

构造函数程序示例：

#include <iostream>
#include <string>

int main()
{
  using namespace std;
  string one("Lottery Winner!");
  cout << one << endl;
  string two(20, '$');
  cout << two << endl;
  string three(one);
  cout << three << endl;
  one += " Oops!";
  cout << one << endl;
  two = "Sorry! That was ";
  three[0] = 'P';
  string four;
  four = two + three;
  cout << four << endl;
  char alls[] = "All's well that ends well";
  string five(alls, 20);
  cout << five << "!\n";
  string six(alls + 6, alls + 10);
  cout << six << ", ";
  string seven(&five[6], &five[10]);
  cout << seven << "...\n";
  string eight(four, 7, 16);
  cout << eight << " in motion!" << endl;
  return 0;
}

string类输入：

C-风格的字符串输入：

char info[100];

cin >> info;

cin.getline(info, 100);

cin.get(info, 100);

对于string对象：

string stuff;

cin >> stuff;

getline(cin, stuff);

指定边界：

c-string: cin.getline(info, 100, ':');

getline(stuff, ':')

string的getline自动调整大小。而c-风格的不行

string对象的最大长度是由string::npos指定的，通常是unsigned int值

string的 operator>>()

文件读取示例：

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>

int main()
{
  using namespace std;
  ifstream fin;
  fin.open("tobuy.txt");
  if (fin.is_open() == false)
  {
    cerr << "Can't open file. Bye.\n";
    exit(EXIT_FAILURE);
  }
  string item;
  int count = 0;
  getline(fin, item, ':');
  while (fin)
  {
    ++count;
    cout << count << ": " << item << endl;
    getline(fin, item, ':');
  }
  cout << "Done\n";
  fin.close();
  return 0;
}

tobuy.txt：

sardines:chocolate ice cream:pop corn:leeks:
cottage cheese:olive oil:butter:tofu:

输出结果

先完结