Operator Overloading part 3(Chapter 12 of Thinking in C++)

  1 #include <string>
  2 #include <iostream>
  3 using namespace std;
  4 
  5 class Dog
  6 {
  7     string nm;
  8     int refcount;
  9     Dog(const string& name) : nm(name), refcount(1) 
 10     {
 11         cout << "Creating Dog:" << *this << endl;
 12     }
 13 
 14     Dog& operator=(const Dog& rv);
 15 public:
 16     static Dog* make(const string& name)
 17     {
 18         return new Dog(name);
 19     }
 20 
 21     Dog(const Dog& d) : nm(d.nm + " copy"), refcount(1)
 22     {
 23         cout << "Dog copy-constructor: " << *this << endl;
 24     }
 25 
 26     ~Dog()
 27     {
 28         cout << "Deleting Dog: " << *this << endl;
 29     }
 30 
 31     void attach()
 32     {
 33         ++refcount;
 34         cout << "Attached Dog:" << *this << endl;
 35     }
 36 
 37     void detach()
 38     {
 39         cout << "Detaching Dog: " << *this << endl;
 40         if(--refcount == 0)
 41         {
 42             delete this;
 43         }
 44     }
 45 
 46     Dog* unalias()
 47     {
 48         cout << "Unaliasing Dog: " << *this << endl;
 49         if(refcount == 1)
 50         {
 51             return this;
 52         }
 53         --refcount;
 54         return new Dog(*this);
 55     }
 56 
 57     void rename(const string& newName)
 58     {
 59         nm = newName;
 60         cout << "Dog renamed to " << *this << endl;
 61     }
 62 
 63     friend ostream& operator<<(ostream& os, const Dog& d)
 64     {
 65         return os << "[" << d.nm << "], rc = " << d.refcount;
 66     }
 67 };
 68 
 69 
 70 class DogHouse
 71 {
 72     Dog* p;
 73     string houseName;
 74 public:
 75     DogHouse(Dog* dog, const string& house) : p(dog), houseName(house)
 76     {
 77         cout << "Creating DogHouse: " << *this << endl;
 78     }
 79 
 80     DogHouse(const DogHouse& dh) : p(dh.p), houseName("copy-constructed " + dh.houseName)
 81     {
 82         p->attach();
 83         cout << "DogHouse copy-constructed: " << *this << endl;
 84     }
 85 
 86     DogHouse& operator=(const DogHouse& dh)
 87     {
 88         if(&dh != this)
 89         {
 90             houseName = dh.houseName + " assigned";
 91             p->detach();
 92             p = dh.p;
 93             p->attach();
 94         }
 95 
 96         cout << "DogHouse operator= : " << *this << endl;
 97         return *this;
 98     }
 99 
100     ~DogHouse()
101     {
102         cout << "DogHouse destructor: " << *this << endl;
103         p->detach();
104     }
105 
106     void renameHouse(const string& newName)
107     {
108         houseName = newName;
109     }
110 
111     void unalias()
112     {
113         p = p->unalias();
114     }
115 
116     void renameDog(const string& newName)
117     {
118         unalias();
119         p->rename(newName);
120     }
121 
122     Dog* getDog()
123     {
124         unalias();
125         return p;
126     }
127 
128     friend ostream& operator<<(ostream& os, const DogHouse& dh)
129     {
130         return os << "[" << dh.houseName << "] contains " << *dh.p;
131     }
132 
133 };
134 
135 int main()
136 {
137     DogHouse fidos(Dog::make("Fido"), "FidoHouse"), spots(Dog::make("Spot"), "SpotHouse");
138     cout << "Entering copy-construction" << endl;
139     DogHouse bobs(fidos);
140     cout << "After copy-constructing bobs" << endl;
141     cout << "fidos:" << fidos << endl;
142     cout << "spots:" << spots << endl;
143     cout << "bobs:" << bobs << endl;
144     cout << "Entering spots = fidos" << endl;
145     spots = fidos;
146     cout << "After spots = fidos" << endl;
147     cout << "spots:" << spots << endl;
148     cout << "Entering self-assignment" << endl;
149     bobs = bobs;
150     cout << "After self-assignment" << endl;
151     cout << "bobs:" << bobs << endl;
152     // Comment out the following lines:
153     cout << "Entering rename(\"Bob\")" << endl;
154     bobs.getDog()->rename("Bob");
155     cout << "After rename(\"Bob\")" << endl;
156 }