Sams Teach Yourself C++ in 21 Days

Advanced Inheritance 587

16

41: // ConstructorCount++;

42: }

43:

44: // private (helper) constructor, used only by

45: // class methods for creating a new string of

46: // required size. Null filled.

47: String::String(int len)

48: {

49: itsString = new char[len+1];

50: for (int i = 0; i<=len; i++)

51: itsString[i] = ‘\0’;

52: itsLen=len;

53: // cout << “\tString(int) constructor” << endl;

54: // ConstructorCount++;

55: }

56:

57: // Converts a character array to a String

58: String::String(const char * const cString)

59: {

60: itsLen = strlen(cString);

61: itsString = new char[itsLen+1];

62: for (int i = 0; i<itsLen; i++)

63: itsString[i] = cString[i];

64: itsString[itsLen]=’\0’;

65: // cout << “\tString(char*) constructor” << endl;

66: // ConstructorCount++;

67: }

68:

69: // copy constructor

70: String::String (const String & rhs)

71: {

72: itsLen=rhs.GetLen();

73: itsString = new char[itsLen+1];

74: for (int i = 0; i<itsLen;i++)

75: itsString[i] = rhs[i];

76: itsString[itsLen] = ‘\0’;

77: // cout << “\tString(String&) constructor” << endl;

78: // ConstructorCount++;

79: }

80:

81: // destructor, frees allocated memory

82: String::~String ()

83: {

84: delete [] itsString;

85: itsLen = 0;

86: // cout << “\tString destructor” << endl;

87: }

88:

89: // operator equals, frees existing memory

90: // then copies string and size

91: String& String::operator=(const String & rhs)

92: {

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