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Constructor:
Constructors are typically used to initialize member variables of the class to appropriate default values.
Here is an example of a class that has a default constructor:
(A default constructor means that a constructor has no parameters.)
class Fraction{private: int m_nNumerator; int m_nDenominator;public: Fraction() // default constructor { m_nNumerator = 0; m_nDenominator = 1; } int GetNumerator() { return m_nNumerator; } int GetDenominator() { return m_nDenominator; } double GetFraction() { return static_cast<double>(m_nNumerator) / m_nDenominator; }};Destructor:
Destructor is the counterpart to constructors. When a variable goes out of scope, or a dynamically allocated variable is explicitly deleted using the delete keyword, the class destructor is called (if it exists) to help clean up the class before it is removed from memory.
take a look at a simple string class that uses a destructor:
class MyString{private: char *m_pchString; int m_nLength;public: MyString(const char *pchString="") { m_nLength = strlen(pchString) + 1; m_pchString = new char[m_nLength]; strncpy(m_pchString, pchString, m_nLength); m_pchString[m_nLength-1] = '\0'; } ~MyString() // destructor { // We need to deallocate our buffer delete[] m_pchString; // Set m_pchString to null just in case m_pchString = 0; } char* GetString() { return m_pchString; } int GetLength() { return m_nLength; }};
int main(){ MyString cMyName("Alex"); std::cout << "My name is: " << cMyName.GetString() << std::endl; return 0;} // cMyName destructor called here!
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