It is still a study notes for more effective C Terms 30-Proxy Class.
#include
Using namespace std;
Template
Class Array
{
PUBLIC:
Class Proxy
{
PUBLIC:
Proxy (Array & Array, Int Index)
: THEARRAY (Array), ItemIndex (INDEX)
{}
Proxy & operator = (const t & rhs) {THEARRAY.Array [itemindex] = rhs; return * this;} Operator t () const {return thealay.Array [itemIndex];
Friend Ostream & Operator << (Ostream & OS, Const Proxy & RHS) {OS << RHS.THEARRAY [RHS.ITEMINDEX]; RETURN OS;
Private: Array & THEARRAY; INT ITEMINDEX;
Const proxy operator [] "const; proxy operator [] (int index);
Friend Class Proxy; Array (int Dim); ~ array ();
PRIVATE: T * array;
Template
Array
:: Array (int Dim)
{
Array = New T [DIM];
}
Template
Array
:: ~ array ()
{
delete [] array;
}
Template
Array
:: Proxy Array
:: Operator [] (int INDEX)
{
Return Proxy (* this, index);
}
Template
Const array
:: Proxy Array
:: Operator [] (int index) Const
{
Return Proxy (const_cast (* this), index;
}
class Rational {public: Rational (int numerator = 0, int denominator = 1); int numerator () const; int denominator () const; Rational & operator = (const Rational & rhs); friend ostream & operator << (ostream & os, const Rational & RHS);
PUBLIC: INT NUM; INT DENO;
Rational :: Rational (int name): Num (namerator), DENO (Denominator) {std :: cout << "Rational Construct << std :: endl;}
int Rational :: Numerator () const {std :: cout << "numerator:" << Num <
Return 0;
}
INT Rational :: Denominator () const {std :: cout << "Denominator:" << DENO << std :: endl; return 0;}
Rational & Rational :: Operator = (Const Rational & RHS) {Num = rhs.Num; DENO = rhs.deno; return * this;}
Ostream & Operator << (Ostream & OS, Const Rational & Rhs) {OS << rhs.num << "<< rhs.deno; return os;
Int main () {Array
a (5);
a [1] .Numerator (); //
error}
The reason why the error occurring is: Operator [] Returns a proxy object rather than the actual Rational object. But the member function Numerator () and Denominator () are only on the Rational object, not their agent objects.
But I think, why do the compiler not call an implicit conversion function here?
Operator t () const {return thearray.Array [itemindex];
? If the call is called, then the error should not appear.
A simple solution is
Int main () {Array
a (5);
(Rational) a [1]) .Numerator ();
}
