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COMMENT(
Also note that
the example doesn't show where the destructor is called; this action occurs
implicitly when the below function tt(main()) terminates and hence when its
local variable tt(p) ceases to exist.
When tt(printperson()) receives a fully defined tt(Person) object (i.e.,
containing a name, address and phone number), the data are correctly printed.
However, when a tt(Person) object is only partially filled, e.g. with only a
name, tt(printperson()) passes 0-pointers to tt(cout). This unesthetic
feature can be remedied with a little more code:
verb(
void printperson(Person const &p)
{
if (p.name())
cout << "Name : " << p.name() << "\n";
if (p.address())
cout << "Address : " << p.address() << "\n";
if (p.phone())
cout << "Phone : " << p.phone() << "\n";
}
)
Alternatively, the constructor tt(Person::Person()) might initialize the
members to `printable defaults', like tt(" ** undefined ** ").
The destructor, constructor and the class definition are given below.
verb(
// class definition
class Person
{
public:
Person(); // constructor
~Person(); // destructor
// functions to set fields
void setName(string const &n);
void setAddress(string const &a);
void setPhone(string const &p);
// functions to inspect fields
string const &name() const;
string const &address() const;
string const &phone() const;
private:
char *name; // name of person
char *address; // address field
char *phone; // telephone number
};
// constructor
Person::Person()
{
name = 0;
address = 0;
phone = 0;
}
// destructor
Person::~Person()
{
free(name);
free(address);
free(phone);
}
)
END COMMENT)
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