繼承層次中的輸入輸出運算符重載
class A
{
};
class B : public A
{
};
方案一
可對 A 進行重載輸入輸出運算符，然后也對 B 重載相應版本的輸入輸出運算符
方案二
只對 A 進行重載輸入輸出運算符，對 A 定義一個 virtual print 函數，在 B 中也對該 virtual 函數 override
在重載的輸入輸出運算符中調用 virtual print 函數
1 #include <iostream>
2 #include <string>
3 using namespace std;
4
5 class Complex
6 {
7 protected:
8 // private:
9 int nR;
10 int nI;
11 public:
12 Complex(int tmpR = -100, int tmpI = -100);
13 virtual void display();
14 virtual ostream& print(ostream& os) const;
15 friend ostream& operator << (ostream&, const Complex&);
16 };
17
18 class NameComplex : public Complex
19 {
20 private:
21 string strName;
22 public:
23 NameComplex(const string& = "abc", int = -100, int = -100);
24 virtual void display();
25 virtual ostream& print(ostream& os) const;
26 // friend ostream& operator << (ostream&, const NameComplex&);
27 };
28
29 Complex::Complex(int tmpR, int tmpI) : nR(tmpR), nI(tmpI) {}
30
31 void Complex::display()
32 {
33 cout << nR << endl;
34 cout << nI << endl;
35 }
36
37 ostream& Complex::print(ostream& os) const
38 {
39 os << nR << ' ' << nI;
40 return os;
41 }
42
43 /*
44 ostream& operator << (ostream& os, const Complex& rhs)
45 {
46 os << rhs.nR << ' ' << rhs.nI;
47 return os;
48 }
49 */
50
51 ostream& operator << (ostream& os, const Complex& rhs)
52 {
53 return rhs.print(os);
54 }
55
56 NameComplex::NameComplex(const string& str, int nR, int nI) : Complex(nR, nI), strName(str) {}
57
58 void NameComplex::display()
59 {
60 cout << strName << endl;
61 Complex::display();
62 }
63
64 /*
65 ostream& operator << (ostream& os, const NameComplex& rhs)
66 {
67 os << rhs.strName << ' ';
68 operator << (os, static_cast<Complex>(rhs));
69 return os;
70 }
71 */
72
73 ostream& NameComplex::print(ostream& os) const
74 {
75 os << strName << ' ';
76 return Complex::print(os);
77 }
78
79 int main()
80 {
81 Complex a;
82 cout << a << endl;
83
84 NameComplex b;
85 cout << b << endl;
86 }
http://topic.csdn.net/u/20110627/22/c4c0b809-13f4-482d-aa26-5faf5c1fc0f0.html?54375
posted on 2011-06-27 23:44
unixfy 閱讀(243)
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