Question

I am currently stuck with this portion of my assignment:

Pointers review: to help determine how many fields are presented from the form at run time, the program will count the '=' signs from the QUERY_STRING and dynamically create a name_value_pairs array of cnt elements to be used by parse() and param(). Here is what to do, in order:

1. As directed above, make a back up of the work so far and work with the new version named retrieve_form_OOP_2.cpp.
2. These additions to the class will require a 'private:' area to hold the cnt and qs variables, a 'constructor' function, as well as additional functions to access the variables in the 'private' area, as explained in videos at 1b and 1c.
3. Cheat sheet for the 'class' modification - adopt this structure to help modify your existing class:
   • class_start.txt
4. The way to approach these changes is as always - one step at a time:
   1. First create the constructor by adding following lines (from class_start.txt) into your existing class :
      • cout << "Content-type:text/html\n\n"; set_qs(getenv("QUERY_STRING")); cout << "debug with get_qs: " << get_qs();
   2. Next create the two functions set_qs() and get_qs().
   3. Now compile until it does and runs giving the proper debug message.
   4. Use similar approach with 'cnt' (as get_qs() and set_qs() above) - will need function 'how_many()', which can be adapted from parse() fairly easily. Note: while working on set_cnt() and get_cnt(), code how_many() to simply return a 3 (and comment everything else). Once set_cnt() and get_cnt() are working (based on the debug statements), code how_many() to find the 'real' number of = signs in qs. Makes sense?
   5. Once cnt works, then parse and param will need modifying to replace the variable by its call get_cnt() to produce the value from 'private:'
5. The next step would be to create the dynamic array, of which function will also reside in the class. But the calls will come from main() from this point. Note: no need to use pointer notation with this dynamic array - treat it as a regular array (which it is, of course, since arrays are pointers).
6. Beware of the wo.get_cnt() and other object substitutions in main as well

This is the code for class WebApps that I have so far:

//Libraries

   #include <iomanip>

   #include <iostream>

   #include <cstring>

   #include <cstdlib>

   #include <string>

   #include <cctype> //for isalnum()

   using namespace std;

struct FIELDS {

   string name;

   string value;

};

const int cnt = 3; //should be set to the number of fields in form

class WebApps{

   public:

WebApps()

{

   cout << "Content-type:text/html\n\n";   

   set_qs(getenv("QUERY_STRING"));

//cout << "debug with get_qs: " << get_qs();

   set_cnt(how_many(get_qs()));

//cout << "<br>debug with get_cnt: " << get_cnt();  

}

void set_qs(string f_getenv) {

qs = f_getenv;

   }

void set_cnt(int f_how_many) {

cnt = f_how_many;

   }

string get_qs() {

return qs;

}

int get_cnt() {

return cnt;

   }

/////////////////////////////////////////////////////

// how_many()

// This will count and return how many = signs in the QUERYSTRING

////////////////////////////////////////////////////

int how_many (string f_qs) {

//initialize variables

int i = 0;

int count = 0;

while (i<strlen(f_qs)) {

if(f_qs.at(i) == "=") count++;

   }

   returns count; //returns the count or 0 if f_qs is empty

   }

////////////////////////////////////////////////////

//create_array

// Creates a dynamic array  

FIELDS * create_array (int f_cnt)

{

   FIELDS fields[f_cnt];

   return 0;

}

/////////////////////////////////////////////

// parse()

// This will separate the name/value pairs found after the ? in the URL

/////////////////////////////////////////////   

void parse (string qs, FIELDS f_name_value_pairs []) {

cout << "debug in parse <br>\n"<< endl;

string name, value;

int start_pos = 0, pos;

for (int counter = 0; counter < cnt; counter++) {

pos = qs.find("=", start_pos);

name = qs.substr(start_pos, pos - start_pos);

f_name_value_pairs[counter].name = name;

cout << "name: " << name << " " << endl;

start_pos = pos + 1;

pos = qs.find("&", start_pos);

if (pos == string::npos){

pos = qs.length();

   }

value = qs.substr(start_pos, pos - start_pos);

f_name_value_pairs[counter].value = value; //store the name of parameter in array

cout << "value: " << value << "<br>" << endl;

start_pos = pos + 1;

   }

   }

   //value = qs.substr(startPos, qs.length() - startPos);

   //cout << "value: " << value << endl;

string param(string lookUp, FIELDS f_name_value_pairs[], int f_cnt) {

string f_value;

bool found = false;

for (int index=0; index < f_cnt; index++) {

if(f_name_value_pairs[index].name != lookUp);

   //do nothing

else

   {

found = true;

f_value = f_name_value_pairs[index].value;

   }

   }  

   if (found)

return f_value;

   else

return "";

   }

   private: // private access specifier

string qs; // holds the QUERY_STRING

int cnt; // holds the number of fields found from the form

};

Answer 1

SOLUTION:

class WebApps {

private: // private access specifier

string qs; // holds the QUERY_STRING

int cnt; // holds the number of fields found from the form

public: //public access specifier.   

WebApps (){ //constructor

  

cout << "Content-type:text/html\n\n"; //get ready to print on browser

set_qs(getenv("QUERY_STRING")); //save string to private qs

//cout << "debug with get_qs: " << get_qs(); //testing functions

set_cnt(how_many(get_qs()));

//cout << "<br>debug with get_cnt: " << get_cnt();//testing functions

}

  

//setter method for qs

void set_qs(string f_getenv) {

qs = f_getenv;

}

//setter method for cnt

void set_cnt(int f_how_many) {

cnt = f_how_many;

}

string get_qs() {

return qs;

}

int get_cnt() {

return cnt;

}

/////////////////////////////////////////////////////

// how_many()

// This will count and return how many = signs in the QUERYSTRING

////////////////////////////////////////////////////

int how_many (string f_qs)

{

int i = 0;

int count =0;

while (i < strlen(f_qs)){

if(f_qs.at(i) == '=') count++;

}

returns count;//returns count or 0 if f_qs is empty

}

////////////////////////////////////////////////////

//create_array

// Creates a dynamic array

////////////////////////////////////////////////////

FIELDS * create_array (int f_cnt)

{

FIELDS fields[f_cnt];

return fields;

}

  

/////////////////////////////////////////////

// parse()

// This will separate the name/value pairs found after the ? in the URL

/////////////////////////////////////////////

void parse (string f_qs, FIELDS f_name_value_pairs [])

{

int pos = 0;

string token = "";

int count =0;

while ((pos = s.find(",")) != std::string::npos) {

token = f_qs.substr(0, pos);

f_qs.erase(0, pos + 1);

int pos2 = 0;

string token2 = token;

while ((pos2 = token.find("=")) != std::string::npos) {

token2 = token.substr(0, pos2);

token.erase(0, pos+1);

FIELDS field;

field.key = token2;

field.value = token;

f_name_value_pairs[count++] = field;

}

}

}

  

/////////////////////////////////////////////

// param()

// Will receive the value for any given form field

/////////////////////////////////////////////

string param(string lookUp, FIELDS f_name_value_pairs [], int f_cnt)

{

for(int i=0;i<f_cnt;i++)

if(strcmp(loopup, f_name_value_pairs[i].key) == 0)

return f_name_value_pairs[i].value;

}

  

  

};

class FIELDS{

public:

string key;

string value;

};