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Second C++ demo - heap v stack, char handling, this, static
this example from a Well House Consultants training course
More on this [link]
Source code: act_02.cpp Module: C051
using namespace std;

#include <iostream>
#include <string>

/*
Taking the earlier example, we have added four more significant
features to our C++ example:

1. Objects can be defined on the heap or on the stack. We used
the heap in the earlier example but this one uses the stack

2. We have added character handling (through pointers and also
through copying strings)

3. Rather than come up with lots of names for the same thing, we
have used "this" to indicate the object variables.

4. We have defined a static variable and method

5. We have shown overloading - multiple methods of the same name
but with different calling sequences.
*/


// Second demo / test - will split into multiple files later

// Define the API to the class
// ---------------------------

class Activity {
        public:
                Activity(char *descriptor, float minutes, float cals);
                Activity(char *descriptor, float minutes, float cals, char *where);
                float getCalpm();
                char *getDesc();
                char *getLocation();
                        // Above, one per object.
                        // Below, one per class!
                static int getCount();
        private:
                float mins;
                float cals;
                char *description; // Option 1 - pointer
                char location[21]; // Option 2 - hold it here
                        // Above, one per object.
                        // Below, one per class!
                static int options_count;
};

// Define the class itself
// -----------------------

// We have modified the name of the variable within the object
// to be the same as the name used in the call (avoids the need
// for lots of different words for the same thing), and we can
// now refer to them as "mins" for the local variable and
// "this->mins" for the object variable

Activity::Activity(char *description, float mins, float cals) {
        Activity::options_count++;
        this->mins = mins;
        this->cals = cals;
         // Remember that following copies just the POINTER and
         // the data remains in variables outside the object space
         // which may have a different persistance.
        this->description = description;
         // Alternative - set up and store string in the object
         // (a) String is with object [better than other approach]
         // (b) String has fixed length [worse than other approach]
        *(this->location) = '\0';
        }

Activity::Activity(char *description, float mins, float cals, char *where) {
        Activity::options_count++;
        this->mins = mins;
        this->cals = cals;
        this->description = description;
        // we need to copy the string! ...
        strcpy(this->location,where);
        }

float Activity::getCalpm() {
        return cals / mins;
        }

char * Activity::getDesc() {
        return description;
        }

char * Activity::getLocation() {
        return location;
        }

int Activity::getCount() {
        return options_count;
        }

/* Please note that using a static variable to count the number
of objects of a type you have is pretty nasty ... but it makes a
good demo. Typically, static variables will be internal things
like the name of a temporary work file or a database password. If
you use them as a counter, you have a problem when you user wants
fo count all of the object <i>with a certain characteristic!</i> */


int Activity::options_count = 0;

// Main test program - what do want to be able to do with activities?
// ------------------------------------------------------------------

int main () {

        // Set up objects on the stack / current area.
        // This means the object's data is LOST at function end!

        Activity Ramble = Activity("Walk da dog",60.0,1000.0," in da field");
        Activity Foxtrot = Activity("With Widdy",3.0,400.0);

        cout << Ramble.getDesc() << " burns up " <<
                        Ramble.getCalpm() << " c.p.m at " <<
                        Ramble.getLocation() << endl;
        cout << Foxtrot.getDesc() << " burns up " <<
                        Foxtrot.getCalpm() << " c.p.m at " <<
                        Foxtrot.getLocation() << endl;
        cout << "Object count " << Activity::getCount() << endl ;
        return 0;
        }

/* Sample Output

wizard:cppcsr graham$ ./act_02
Walk da dog burns up 16.6667 c.p.m at in da field
With Widdy burns up 133.333 c.p.m at
Object count 2
wizard:cppcsr graham$

*/

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