new and strings

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new and strings

This program should seperate a string such as 2/3 into 2 and 3. When I run it and enter data for the string, I get an error message, the one that asks you if you want to send an error report.

I got the example from a book but the book used char types and I tried to use string types.

Note: use_String_Parser() is the equivelent if main. (this is called by another program.

#include "stdafx.h"

#include <String.h>

void use_String_Parser();

class StringParser{

private:

//Data Members

int m_pos;

string m_input_str;

string m_delimeters;

public:

//Public Functions

string *get();

int more() {return (m_input_str[m_pos] != '\0');}

void reset() {m_pos = 0;}

//Constructors

StringParser(string m_inp, string delim) {m_input_str = m_inp; m_delimeters = delim; m_pos = 0;}

StringParser(string inp) {m_input_str = inp; m_delimeters = ','; m_pos = 0;}

};

void use_String_Parser(){

string v_input_string;

string *p;

//Delayed: {StringParser parser(input_str, "/");}

cout << "Enter input line: ";

getline(cin, v_input_string);

StringParser parser(v_input_string, "/");

while (parser.more()){

p = parser.get();

cout << p << endl;

delete [] p;

}

}

string *StringParser::get(){

int j = 0;

string *new_str;

new_str = new string;

while (strchr(m_delimeters.c_str(), m_input_str[m_pos]))

++m_pos;

while (m_input_str[m_pos] != '\0' && !strchr(m_delimeters.c_str(), m_input_str[m_pos]))

new_str[++j] = m_input_str[++m_pos];

new_str[j] = '\0';

return new_str;

}


Answer this question

new and strings

  • gheese

    std::getline()

    index of source string is less than string size

    dynamically allocated string object is sized correctly

    Kuphryn

  • carina9138

    string *new_str = new string;

    makes new_str a pointer to a string object, not a pointer to an array of characters.  In addition, as Kuphryn points out, you cannot index characters the way you're doing because you'd be indexing an array of string objects (of which there is only the one you allocated).  Furthermore, the corresponding delete should be delete p, not delete[] p.

    It's okay to return string objects instead a pointer to string objects.  The whole point of using string is that it manages the "pointing to an array of characters" business for you and makes strings act more like first-class objects within the language.  You should use string::append() to add characters to the string.

    If it helps, here's a simpler implementation that I use on relatively short 8-bit character strings.  It is patterned after System.String.Split in the .NET framework.

    vector<string> Split(     const string& input, const string& delimiters )
    {
       vector<string> arr;
       char* tokenizeCopy = strdup( input.c_str() );
       char* pos = tokenizeCopy;
       char* token;
       do
       {
          token = strtok( pos, delimiters.c_str() );
          pos = 0;
          if( token != 0 )
          {
                arr.push_back( token );
          }
       }     while( token != 0 );

       free( tokenizeCopy );
       return arr;
    }     
  • new and strings
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