Sams Teach Yourself C++ in 21 Days

Advanced Inheritance 541

16

117: // on const objects (see copy constructor!)

118: char String::operator[](int offset) const

119: {

120: if (offset > itsLen)

121: return itsString[itsLen-1];

122: else

123: return itsString[offset];

124: }

125:

126: // creates a new string by adding current

127: // string to rhs

128: String String::operator+(const String& rhs)

129: {

130: int totalLen = itsLen + rhs.GetLen();

131: String temp(totalLen);

132: int i, j;

133: for (i = 0; i<itsLen; i++)

134: temp[i] = itsString[i];

135: for (j = 0; j<rhs.GetLen(); j++, i++)

136: temp[i] = rhs[j];

137: temp[totalLen]=’\0’;

138: return temp;

139: }

140:

141: // changes current string, returns nothing

142: void String::operator+=(const String& rhs)

143: {

144: unsigned short rhsLen = rhs.GetLen();

145: unsigned short totalLen = itsLen + rhsLen;

146: String temp(totalLen);

147: int i, j;

148: for (i = 0; i<itsLen; i++)

149: temp[i] = itsString[i];

150: for (j = 0; j<rhs.GetLen(); j++, i++)

151: temp[i] = rhs[i-itsLen];

152: temp[totalLen]=’\0’;

153: *this = temp;

154: }

155:

156: // int String::ConstructorCount = 0;

Put the code from Listing 16.1 into a file called MyString.hpp. Then, any

time you need the Stringclass, you can include Listing 16.1 by using

#include “MyString.hpp”, such as in this listing. You might notice a number

of commented lines in this listing. The purpose of these lines are explained

throughout today’s lesson.

NOTE

LISTING16.1 continued