C++ String Methods

1. OOP terminology
   1. Using object-oriented programming (OOP) terminology, string is a class
   2. Creating a string means creating an object
   3. Functions that work on an object are called methods

      // General syntax
      object.method();
      

2. Below is a subset of string methods; see this string reference for a complete list
   1. Determine the length of a string
      
      int ← length() - Returns the number of characters in the string (size() does same thing)

      string s = "hello";
      int len = s.length();    // 5
      len = s.size();   // 5
      

   2. Determine if a string is empty
      
      bool ← empty() - Returns true if the string has a length of 0, false otherwise

      string s = "";
      if (s.empty())    // true
      	cout << "s is empty";
      

   3. Erase a portion of a string
      
      erase(int start, int numChars) - Erases all chars beginning at start and going to the right. numChars limit is optional

      string s = "erase this";
      s.erase(0, 6);    // Leaves "this"
      s.erase(2);       // Leaves "th"
      

   4. Get a substring of a larger string
      
      string ← substr(int start, int numChars) - Returns the string beginning at start that is numChars in length. numChars is optional

      string a = "a nice play";
      string b = a.substr(2);   // "nice play"
      b = a.substr(2, 4);       // "nice"
      

   5. Finding a string within a string
      
      int ← find(string find, int start) - Returns the starting location of the first occurance of find in the string, string::npos if find string could not be found. start is the optional starting location

      string s = "this is a test";
      int pos = s.find("is");    // 2
      pos = s.find("is", 3);     // 5
      
      pos = s.find("xyz");
      if (pos == string::npos)
      	cout << "Could not find xyz";
      

   6. Finding one char out of a group of chars in a string
      
      int ← find_first_of(string find, int start) - Returns the first location of any chars in the find in the string, string::npos if none of the chars could be found. start is the optional starting location

      string s = "this is a test";
      int pos = s.find_first_of("iou");    // 2
      pos = s.find_first_of("iou", 3);     // 5
      
      pos = s.find_first_of("xyz");
      if (pos == string::npos)
      	cout << "Could not find x, y, or z";
      

   7. Replace chars from a string with another string
      
      replace(int start, int numChars, string replacement) - Replaces the chars beginning at start that is numChars in length with replacement

      string s = "this is a test";
      s.replace(5, 2, "was");    // "this was a test"
      

3. Converting strings to int/double and vice versa
   1. to_string converts an int or double into a string

      string s = to_string(100);     // "100"
      s = to_string(23.6);           // "23.60000"
      

      
      Note: If you need control over decimal places, use stringstream
   2. stod converts a string to a double

      double x = stod("23.6");      // 23.6
      

   3. stoi converts a string to an int

      int x = stoi("100");      // 100