Skip to content

Latest commit

 

History

History
120 lines (99 loc) · 3.93 KB

16 Lesson16 Notes.md

File metadata and controls

120 lines (99 loc) · 3.93 KB
Raw

Lesson 16 - The STL String Class

The Need for String Manipulation Classes

Typically, to generate a string, the following two syntaxes have their own flaws:
char staticName [20];
char* dynamicName = new char [arrayLen];

Instantiating the STL String and Making Copies

const char* constCStyleString = "Hello String!";
// Initialization
std::string strFromConst(constCStyleString);
// or
std::string strFromConst = constCStyleString;
// or 
std::string str2("Hello String!");
// or 
std::string str2 = "Hello String!";

// use one string object to initialize another: 
std::string str2Copy (str2);

// Initialize a string to the first 5 characters of another 
std::string strPartialCopy (constCStyleString, 5);

// Initialize a string object to contain 10 'a's 
std::string strRepeatChars (10, 'a');
// or
std::string strRepeatChars (10, "day");

To use character strings to copy from another of the same kind:

const char* constCStyleString = "Hello World!";

// To create a copy, first allocate memory for one... 
char* copy = new char [strlen (constCStyleString) + 1]; 

strcpy (copy, constCStyleString); // The copy step
// deallocate memory after using copy 
delete [] copy;

Accessing Character Contents of a std::string

string stlString ("Hello String");

for(size_t charCounter = 0; charCounter < stlString.length(); ++ charCounter) {
  cout << stlString [charCounter] << endl;
}

// Access the contents of a string using iterators
for(auto charLocator = stlString.cbegin(); charLocator != stlString.cend(); ++ charLocator) {
  cout << *charLocator << endl;
}

Understand size_t
Alias of one of the fundamental unsigned integer types.
size_t is the type returned by the sizeof operator and is widely used in the standard library to represent sizes and counts.

Concatenating One String to Another Using append()

string sampleStr1 ("Hello"); 
string sampleStr2 (" String! ");
// use std::string::operator+=
sampleStr1 += sampleStr2;
// alternatively use std::string::append() 
sampleStr1.append (sampleStr2); // (overloaded for char* too)

Finding a Character or Substring in a String Using find()

// Find substring "day" in sampleStr, starting at position 0 
size_t charPos = sampleStr.find("day", 0);

// Check if the substring was found, compare against string::npos 
if (charPos != string::npos) {  // std::string::npos (that is actually –1)
  // ...
}

// find() all with while
while(charPos != string::npos) {
  // Make find() search forward from the next character onwards
  size_t searchOffset = charPos + 1;
  charPos = sampleStr.find ("day", searchOffset);
}

Truncating an STL string Using erase()

string sampleStr ("Hello String! Wake up to a beautiful day!");

  • sampleStr.erase (13, 28); // Hello String!
  • sampleStr.erase (iCharS); // iterator points to a specific character
  • sampleStr.erase (sampleStr.begin (), sampleStr.end ()); // erase from begin to end

String Reversal with reverse()

reverse (sampleStr.begin (), sampleStr.end ());

String Case Conversion Using transform()

string inStr = "Hello World!";
// switch to upper case
transform(inStr.begin(), inStr.end(), inStr.begin(), ::toupper);
// switch to lower case
transform(inStr.begin(), inStr.end(), inStr.begin(), ::tolower);

Read More: https://en.cppreference.com/w/cpp/algorithm/transform

Template-Based Implementation of an STL String

template<class _Elem, class _Traits, class _Ax> class basic_string

C++14 operator ""s in std::string

Operator ""s that convert the string contained within the quotes, in entirety.

string str1("Traditional string \0 initialization");  // Str1: Traditional string Length: 19
string str2("C++14 \0 initialization using literals"s);  // Str2: C++14 initialization using literals Length: 37

Tips

  • Remember to include <algorithm> when you use std::reverse()
  • Can use auto to replace std::string::iterator