Bruce Eckel's Thinking in C++, 2nd Ed | Contents | Prev | Next |
//: C24:Recycle2.cpp // Chapter 14 example w/ RTTI #include <fstream> #include <vector> #include <typeinfo> #include <cstdlib> #include <ctime> #include "../purge.h" using namespace std; ofstream out("recycle2.out"); class Trash { float _weight; public: Trash(float wt) : _weight(wt) {} virtual float value() const = 0; float weight() const { return _weight; } virtual ~Trash() { out << "~Trash()\n"; } }; class Aluminum : public Trash { static float val; public: Aluminum(float wt) : Trash(wt) {} float value() const { return val; } static void value(int newval) { val = newval; } }; float Aluminum::val = 1.67; class Paper : public Trash { static float val; public: Paper(float wt) : Trash(wt) {} float value() const { return val; } static void value(int newval) { val = newval; } }; float Paper::val = 0.10; class Glass : public Trash { static float val; public: Glass(float wt) : Trash(wt) {} float value() const { return val; } static void value(int newval) { val = newval; } }; float Glass::val = 0.23; // Sums up the value of the Trash in a bin: template<class Container> void SumValue(Container& bin, ostream& os) { typename Container::iterator tally = bin.begin(); float val = 0; while(tally != bin.end()) { val += (*tally)->weight() * (*tally)->value(); os << "weight of " << typeid(*tally).name() << " = " << (*tally)->weight() << endl; tally++; } os << "Total value = " << val << endl; } int main() { srand(time(0)); // Seed random number generator vector<Trash*> bin; // Fill up the Trash bin: for(int i = 0; i < 30; i++) switch(rand() % 3) { case 0 : bin.push_back(new Aluminum(rand() % 100)); break; case 1 : bin.push_back(new Paper(rand() % 100)); break; case 2 : bin.push_back(new Glass(rand() % 100)); break; } // Note difference w/ chapter 14: Bins hold // exact type of object, not base type: vector<Glass*> glassBin; vector<Paper*> paperBin; vector<Aluminum*> alBin; vector<Trash*>::iterator sorter = bin.begin(); // Sort the Trash: while(sorter != bin.end()) { Aluminum* ap = dynamic_cast<Aluminum*>(*sorter); Paper* pp = dynamic_cast<Paper*>(*sorter); Glass* gp = dynamic_cast<Glass*>(*sorter); if(ap) alBin.push_back(ap); if(pp) paperBin.push_back(pp); if(gp) glassBin.push_back(gp); sorter++; } SumValue(alBin, out); SumValue(paperBin, out); SumValue(glassBin, out); SumValue(bin, out); purge(bin); } ///:~