1 c++继承经典例子
2 #include <iostream.h>
3 class Base
4 {
5 private:
6 int b_number;
7 public:
8 Base( ){}
9 Base(int i) : b_number (i) { }
10 int get_number( ) {return b_number;}
11 void print( ) {cout << b_number << endl;}
12 };
13
14 class Derived : public Base
15 {
16 private:
17 int d_number;
18 public:
19 // constructor, initializer used to initialize the base part of a Derived object.
20 Derived( int i, int j ) : Base(i), d_number(j) { };
21 // a new member function that overrides the print( ) function in Base
22 void print( )
23 {
24 cout << get_number( ) << " ";
25 // access number through get_number( )
26 cout << d_number << endl;
27 }
28 };
29 int main( )
30 {
31 Base a(2);
32 Derived b(3, 4);
33 cout << "a is ";
34 a.print( ); // print( ) in Base
35 cout << "b is ";
36 b.print( ); // print( ) in Derived
37 cout << "base part of b is ";
38 b.Base::print( ); // print( ) in Base
39 return 0;
40 }
41
42
43 没有虚析构函数，继承类没有析构
44 //Example: non- virtual destructors for dynamically allocated objects.
45
46 #include <iostream.h>
47 #include <string.h>
48 class Thing
49 { public:
50 virtual void what_Am_I( ) {cout << "I am a Thing./n";}
51 ~Thing(){cout<<"Thing destructor"<<endl;}
52 };
53 class Animal : public Thing
54 {
55 public:
56 virtual void what_Am_I( ) {cout << "I am an Animal./n";}
57 ~Animal(){cout<<"Animal destructor"<<endl;}
58 };
59 void main( )
60 {
61 Thing *t =new Thing;
62 Animal*x = new Animal;
63 Thing* array[2];
64 array[0] = t; // base pointer
65 array[1] = x;
66 for (int i=0; i<2; i++) array->what_Am_I( ) ;
67 delete array[0];
68 delete array[1];
69 return ;
70 }
71
72
73 纯虚函数，多态
74 #include <iostream.h>
75 #include <math.h>
76 class Point
77 {
78 private:
79 double x;
80 double y;
81 public:
82 Point(double i, double j) : x(i), y(j) { }
83 void print( ) const
84 { cout << "(" << x << ", " << y << ")"; }
85 };
86 class Figure
87 {
88 private:
89 Point center;
90 public:
91 Figure (double i = 0, double j = 0) : center(i, j) { }
92
93 Point& location( )
94 {
95 return center;
96 } // return an lvalue
97 void move(Point p)
98 {
99 center = p;
100 draw( );
101 }
102 virtual void draw( ) = 0; // draw the figure
103 virtual void rotate(double) = 0;
104 // rotate the figure by an angle
105 };
106 class Circle : public Figure
107 {
108 private:
109 double radius;
110 public:
111 Circle(double i = 0, double j = 0, double r = 0) : Figure(i, j), radius(r) { }
112 void draw( )
113 {
114 cout << "A circle with center ";
115 location( ).print( );
116 cout << " and radius " << radius << endl;
117 }
118 void rotate(double)
119 {
120 cout << "no effect./n";
121 } // must be defined
122 };
123 class Square : public Figure
124 {
125 private:
126 double side; // length of the side
127 double angle; // the angle between a side and the x-axis
128 public:
129 Square(double i = 0, double j = 0, double d = 0, double a = 0) : Figure(i, j), side(d), angle(a) { }
130 void draw( )
131 {
132 cout << "A square with center ";
133 location( ).print( );
134 cout << " side length " << side << "./n"
135 << "The angle between one side and the X-axis is " << angle << endl;
136 }
137 void rotate(double a)
138 {
139 angle += a;
140 cout << "The angle between one side and the X-axis is " << angle << endl;
141 }
142 void vertices( )
143 {
144 cout << "The vertices of the square are:/n";
145 // calculate coordinates of the vertices of the square
146 }
147 };
148 int main( )
149 {
150 Circle c(1, 2, 3);
151 Square s(4, 5, 6);
152 Figure *f = &c, &g = s;
153 f -> draw( );
154 f -> move(Point(2, 2));
155 g.draw( );
156 g.rotate(1);
157
158 s.vertices( );
159 // Cannot use g here since vertices( ) is not a member of Figure.
160 return 0;
161 }
162 ////////////////////////////////////////////////////////////////////
163 #include <iostream.h>
164 #include <string.h>
165 class Thing
166 {
167 public:
168 virtual void what_Am_I( ) {cout << "I am a Thing./n";}
169 ~Thing(){cout<<"Thing destructor"<<endl;}
170 };
171 class Animal : public Thing
172 {
173 public:
174 virtual void what_Am_I( ) {cout << "I am an Animal./n";}
175 ~Animal(){cout<<"Animal destructor"<<endl;}
176 };
177 void main( )
178 {
179 Thing t ;
180 Animal x ;
181 Thing* array[2];
182 array[0] = &t; // base pointer
183 array[1] = &x;
184 for (int i=0; i<2; i++) array->what_Am_I( ) ;
185 return ;
186 }
187
188
189 多继承
190 #include <iostream.h>
191 class A
192 {
193 private:
194 int a;
195 public:
196 A(int i) : a(i) { }
197 virtual void print( ) {cout << a << endl;}
198 int get_a( ) {return a;}
199 };
200 class B
201 {
202 private:
203 int b;
204 public:
205 B(int j) : b(j) { }
206 void print( ) {cout << b << endl;}
207 int get_b( ) {return b;}
208 };
209 class C : public A, public B
210 {
211 int c;
212 public:
213 C(int i, int j, int k) : A(i), B(j), c(k) { }
214 void print( ) {A::print( ); B::print( );}
215 // use print( ) with scope resolution
216 void get_ab( ) {cout << get_a( ) << " " << get_b( ) << endl;}
217 // use get_a( ) and get_b( ) without scope resolution
218 };
219 int main( )
220 {
221 C x(5, 8, 10);
222 A* ap = &x;
223 B* bp = &x;
224 ap -> print( ); // use C::print( );
225 bp -> print( ); // use B::print( );
226 // bp -> A::print( ); // as if x is inherited from B only,
227 // cannot access A::print( );
228 x.A::print( ); // use A::print( );
229 x.get_ab( );
230 return 0;
231 }
232
233
234 共同基类的多继承
235 #include <iostream.h>
236 class R
237 {int r;
238 public:
239 R(int anInt){ r = anInt;};
240 printOn(){ cout<<"r="<<r<<endl;} ; };
241 class A : public R
242 {
243 int a;
244 public:
245 A(int int1,int int2):R(int2){ a = int1;};};
246 class B : public R
247 {
248 int b;
249 public:
250 B(int int1,int int2):R(int2){ b = int1;};};
251 class C : public A, public B
252 {
253 int c;
254 public:
255 C(int int1,int int2, int int3):A(int2,int3), B(int2,int3){ c = int1;}
256 };
257
258 int main( )
259 {
260 int i;
261 R rr(10);
262 A aa(20,30);
263 B bb (40,50);
264 C cc(5, 7, 9);
265 rr.printOn();
266 aa.printOn(); //inherits R printOn
267 bb.printOn(); //inherits R printOn
268 //cc.printOn(); //would give error
269 return 0;}
270
271
272 虚基类
273
274 #include <iostream.h>
275 class R
276 { int r;
277 public:
278 R (int x = 0) : r(x) { } // constructor in R
279 void f( ){ cout<<"r="<<r<<endl;}
280 void printOn(){cout<<"printOn R="<<r<<endl;}
281 };
282 class A : public virtual R
283 { int a;
284 public:
285 A (int x, int y) : R(x), a(y) { } // constructor in A
286 void f( ){ cout<<"a="<<a<<endl;R::f();}
287 };
288 class B : public virtual R
289 {int b;
290 public:
291 B(int x, int z) : R(x), b(z) { }// constructor in B
292 void f( ){ cout<<"b="<<b<<endl;R::f();}
293 };
294 class C : public A, public B
295 { int c;
296 public:
297 // constructor in C, which constructs an R object first
298 C(int x, int y, int z, int w) : R(x), A(x, y), B(x, z), c(w) { }
299
300 void f( ){ cout<<"c="<<c<<endl;A::f(); B::f();}
301 };
302 void main()
303 { R rr(1000);
304 A aa(2222,444);
305 B bb(3333,111);
306 C cc(1212,345,123,45);
307 cc.printOn(); //uses R printOn but only 1 R..no ambiguity
308 cc.f(); // shows multiple call of the R::f()
309 }
310
311 ////////////////////////////////////////
312 #include <iostream.h>
313 class R
314 { int r;
315 public:
316 R (int x = 0) : r(x) { } // constructor in R
317 void f( ){ cout<<"r="<<r<<endl;}
318 };
319 class A : virtual public R
320 { int a ;
321 protected:
322 void fA( ){cout<<"a="<<a<<endl;};
323 public:
324 A (int x, int y) : R(x), a(y) { } // constructor in A
325 void f( ) {fA( ); R::f( );}
326 };
327 class B : virtual public R
328 { int b;
329 protected:
330 void fB( ){cout<<"b="<<b<<endl;};
331 public:
332 B (int x, int y) : R(x), b(y) { } // constructor in A
333 void f( ) {fB( ); R::f( );}
334 };
335
336 class C : public A, public B
337 { int c;
338 protected:
339 void fC( ){ cout<<"c="<<c<<endl;};
340 public:
341 C(int x, int y, int z, int w) : R(x), A(x, y), B(x, z), c(w) { }
342 void f( )
343 {
344 R::f( ); // acts on R stuff only
345 A::fA( ); //acts on A stuff only
346 B::fB( ); // acts on B stuff only
347 fC( ); // acts on C stuff only
348 }
349 };
350 void main()
351 { R rr(1000);
352 A aa(2222,444);
353 B bb(3333,111);
354 C cc(1212,345,123,45);
355 cc.f();
356 }
357
358
359 私有继承
360
361 // Access levels
362 #include <iostream.h>
363 class Base
364 {
365 private:
366 int priv;
367 protected:
368 int prot;
369 int get_priv( ) {return priv;}
370 public:
371 int publ;
372 Base( );
373 Base(int a, int b, int c) : priv(a), prot(b), publ(c) { }
374 int get_prot( ) {return prot;}
375 int get_publ( ) {return publ;}
376 };
377 class Derived1 : private Base // private inheritance
378 {
379 public:
380 Derived1 (int a, int b, int c) : Base(a, b, c) { }
381 int get1_priv( ) {return get_priv( );}
382 // priv not accessible directly
383 int get1_prot( ) {return prot;}
384 int get1_publ( ) {return publ;}
385 };
386 class Leaf1 : public Derived1
387 {
388 public:
389 Leaf1(int a, int b, int c) : Derived1(a, b, c) { }
390 void print( )
391 {
392 cout << "Leaf1 members: " << get1_priv( ) << " "
393 // << get_priv( ) // not accessible
394 << get1_prot( ) << " "
395 // << get_prot( ) // not accessible
396 // << publ // not accessible
397 << get1_publ( ) << endl;
398 } // data members not accessible. get_ functions in Base not accessible
399 };
400 class Derived2 : protected Base // protected inheritance
401 {
402 public:
403 Derived2 (int a, int b, int c) : Base(a, b, c) { }
404 };
405 class Leaf2 : public Derived2
406 {
407 public:
408 Leaf2(int a, int b, int c) : Derived2(a, b, c) { }
409 void print( )
410 {
411 cout << "Leaf2 members: " << get_priv( ) << " "
412 // << priv // not accessible
413 << prot << " "
414 << publ << endl;
415 } // public and protected data members accessible. get_ functions in Base accessible.
416 };
417 class Derived3 : public Base // public inheritance
418 {
419 public:
420 Derived3 (int a, int b, int c) : Base(a, b, c) { }
421 };
422 class Leaf3 : public Derived3
423 {
424 public:
425 Leaf3(int a, int b, int c) : Derived3(a, b, c) { }
426 void print( )
427 {
428 cout << "Leaf3 members: " << get_priv( ) << " "
429 << prot << " "
430 << publ << endl;
431 } // public and protected data members accessible. get_ functions in Base accessible
432 };
433 int main( )
434 {
435 Derived1 d1(1, 2, 3);
436 Derived2 d2(4, 5, 6);
437 Derived3 d3(7, 8, 9);
438 // cout << d1.publ; // not accessible
439 // cout << d1.get_priv( ); // not accessible
440 // cout << d2.publ; // not accessible
441 // cout << d2.get_priv( ); // not accessible
442 cout << d3.publ; // OK
443 cout << d3.get_prot( ); // OK
444 Leaf1 lf1(1, 2, 3);
445 Leaf2 lf2(4, 5, 6);
446 Leaf3 lf3(7, 8, 9);
447 // cout << lf1.publ << endl; // not accessible
448 // cout << lf2.publ << endl; // not accessible
449 cout << lf3.publ << endl; // OK
450 return 0;
451 }
452
453
454 多级继承
455 // Point-Circle-Cylinder
456 #include <iostream.h>
457 // THE POINT CLASS
458 class Point
459 {
460 friend ostream & operator<<(ostream &,Point &);
461 public:
462
463 // constructor
464 Point (double xval =0, double yval=0 )
465 { x=xval; y=yval;};
466 protected: // accessed by derived class
467 double x;
468 double y;
469 };
470 ostream & operator << (ostream & os,
471 Point & apoint)
472 {
473 cout <<" Point:X:Y: "<<apoint.x << ","
474 << apoint.y<< "/n";
475 return os;
476 }
477 //The Circle class inherits from class Point
478 class Circle : public Point
479 {
480 friend ostream & operator<<(ostream &,Circle&);
481 public:
482 Circle (double r=0,double xval=0,double yval=0)
483 :Point(xval,yval), radius(r)
484 {
485 //radius = r;
486 }
487 double area()
488 {
489 return (3.14159* radius *radius);
490 }
491 protected:
492 double radius;
493 };
494
495 //note casting circle to point
496 ostream & operator <<(ostream & os, Circle & aCircle)
497 {
498 cout<< "Circle:radius:" << aCircle.radius;
499 os<< aCircle.x << "/n";
500 os<< aCircle.y << "/n";
501 return os;
502 }
503 // THE CYLINDER CLASS
504 class Cylinder : public Circle
505 {
506 friend ostream & operator << (ostream & ,Cylinder &);
507 public:
508 Cylinder (double hv=0,double rv=0,
509 double xv=0,double yv=0 )
510 : Circle( xv,yv,rv)
511 {
512 height = hv;
513 }
514 double area ( );
515 protected: // may have derived classes
516 double height;
517 };
518 double Cylinder :: area ( )
519 { // Note that cylinder area uses Circle area
520 return 2.0* Circle::area() + 2.0*3.14159* radius*height;
521 }
522 ostream & operator << (ostream & os,
523 Cylinder & acylinder)
524 {
525 cout << "cylinder dimensions: ";
526 cout << "x: " <<acylinder.x;
527 cout << " y: " <<acylinder.y ;
528 cout << " radius: " <<acylinder.radius ;
529 cout << " height: " <<acylinder.height
530 << endl;
531 return os;
532 }
533 int main(void)
534 {
535 Point p(2,3);
536 Circle c(7,6,5);
537 Cylinder cyl(10,11,12,13);
538 cout << p;
539 cout << c;
540 cout << "area of cirle:" << c.area() << endl;
541 cout<< cyl;
542 cout<<"area of cylinder:"<< cyl.area()<<endl ;
543 cout<<"area of cylinder base is "
544 << cyl.Circle::area() << endl;
545 return 0;
546 }
547
548
549 protected 访问控制属性在继承的意义
550
551 //Example of treating derived class object as base class objects. Point------Circle
552 #include <iostream.h>
553 // THE POINT CLASS
554 class Point
555 {
556 friend ostream & operator<<(ostream &,Circle&);
557 public:
558 Point (double xval =0, double yval=0 ) { x=xval; y=yval;};
559 public:
560 void print()
561 {
562 cout <<" Point:X:Y: "<<x << "," <<y<< "/n";
563 }
564 protected: // accessed by derived class
565 double x; double y;
566 };
567 ostream & operator << (ostream & os, Point & apoint)
568 {
569 cout <<" Point:X:Y: "<<apoint.x << ","<< apoint.y<< "/n";
570 return os;
571 }
572
573 //The Circle class inherits from class Point
574 class Circle : public Point
575 {
576 friend ostream & operator<<(ostream &,Circle&);
577 public:
578 Circle (double r=0,double xval=0,double yval=0):Point(xval,yval)
579 { radius = r;};
580 void print()
581 {
582 cout<< "Circle:radius:" <<radius<<endl;
583 cout <<" Point:X:Y: "<<x << "," <<y<< "/n";
584 }
585 double area()
586 { return (3.14159* radius *radius);};
587 protected:
588 double radius;
589 };
590 //note casting circle to point
591 ostream & operator <<(ostream & os, Circle & aCircle)
592 {
593 cout<< "Circle:radius:" << aCircle.radius;
594 cout<< (Point) aCircle << "/n";
595 return os;
596 }
597
598 //We will look at a few main programs based on previous class definitions. Casting and assignments
599 void main (void )
600 {
601 Point p(2,3); cout <<"Point P= "<< p;
602 Point pp(0,0); cout <<"Point PP= "<< pp;
603 Circle c(7,6,5); cout <<"Circle c= "<< c; //radius =7
604 pp = p; cout <<"Point PP= "<< pp; //built in assign =
605 // a circle is a member of the point class so assign a circle to a point.
606 pp = c; //legal; also assignment O.K.
607 cout <<"Point PP= "<< pp;
608 pp= (Point) c; // but better use the cast
609 cout <<"Point PP= "<< pp; //note we get only the point part of the Circle
610 //c = (Circle) pp; // illegal Cannot convert ‘class Point‘ to ‘class Circle‘
611 //c=pp; //illegal assignment not defined
612 Point* p;
613 p = &c;
614 P->print(); //call base class print
615 ((Circle*)p)->print();
616 Point& r = c;
617 r.print();
618 ((Circle&)r).print();
619 }
620
621
622 类的兼容性规则
623
624
625 #include <iostream.h>
626 class Base
627 {
628 public:
629 void func( )
630 {cout << "Base class function./n";}
631 };
632 class Derived : public Base
633 {
634 public:
635 void func( )
636 {cout << "Derived class function./n";}
637 };
638 void foo(Base b)
639 { b.func( ); }
640 int main( )
641 {
642 Derived d;
643 Base b;
644 Base * p = &d;
645 Base& br = d;
646 b = d;
647 b.func( );
648 d.func( );
649 p -> func( );
650 foo(d);
651 br.func( );
652 return 0;
653 }
654
655
656
657
658 虚析构函数，防止内存泄露
659
660
661 #include <iostream.h>
662 #include <string.h>
663 class Base
664 {
665 protected:
666 int id;
667 char * name;
668 public:
669 // default constructor
670 Base(int a = 0, char * s = "") : id(a)
671 {
672 if (!s)
673 {
674 name = NULL;
675 }
676 else
677 {
678 name = new char[strlen(s) + 1];
679 strcpy(name, s);
680 }
681 cout << "base default constructor/n";
682 }
683 // copy constructor
684 Base(const Base& b) : id(b.id)
685 {
686 if (!b.name) { name = NULL; }
687 else
688 {
689 name = new char[strlen(b.name) + 1];
690 strcpy(name, b.name);
691 }
692 cout << "base copy constructor/n";
693 }
694 // destructor
695 ~Base( )
696 {
697 if( name != NULL ) delete [ ] name;
698 cout << "base destructor/n";
699 }
700 const Base& operator= (const Base& b);
701 friend ostream& operator << (ostream&, const Base&);
702 };
703 const Base& Base:perator= (const Base& b)
704 {
705 if (this != &b) // Check if an object is assigned to itself.
706 {
707 id = b.id;
708 delete [ ] name; // Destroy the old object.
709 if (!b.name) { name = NULL; }
710 else
711 {
712 name = new char[strlen(b.name) + 1];
713 strcpy(name, b.name);
714 }
715 }
716 cout << "base assignment operator/n";
717 return *this;
718 }
719 ostream& operator << (ostream& out, const Base& b)
720 {
721 out << "Base member id = " << b.id << endl;
722 out << "Base member name = " << b.name << endl;
723
724 return out;
725 }
726 class Derived : public Base
727 {
728 private:
729 float f;
730 char * label;
731 public:
732 // default constructor
733 Derived(int a = 0, char * s = "", float x = 0, char * t = "") : Base(a, s), f(x)
734 {
735 if (!t) { label = NULL; }
736 else
737 {
738 label = new char [strlen(t) + 1];
739 strcpy(label, t);
740 }
741 cout << "derived default constructor/n";
742 }
743 // copy constructor
744 Derived(const Derived& d) : Base(d), f(d.f)
745 // d used as an instance of Base
746 {
747 if(!d.label) { label = NULL; }
748 else
749 {
750 label = new char [strlen(d.label) + 1];
751 strcpy(label, d.label);
752 }
753 cout << "derived copy constructor/n";
754 }
755 // destructor
756 ~Derived( )
757 {
758 delete [ ] label;
759 cout << "derived destructor/n";
760 }
761 const Derived& operator= (const Derived& d);
762 friend ostream& operator << (ostream&, const Derived&);
763 };
764 const Derived& Derived:perator= (const Derived& d)
765 {
766 if (this != &d)
767 {
768 delete [ ] label;
769 Base:perator=(d); // Assign the Base part of d to the Base
770 // part of the object that calls this operator;
771 f = d.f;
772 if (!d.label) { label = NULL; }
773 else
774 {
775 label = new char [strlen(d.label) + 1];
776 strcpy(label, d.label);
777 }
778 cout << "derived assignment operator/n";
779 }
780 return *this;
781 }
782 ostream& operator << (ostream& out, const Derived& d)
783 {
784 out << (Base)d; // Convert d to Base object to output Base members.
785 out << "Derived member f = " << d.f << endl;
786 out << "Derived member label = " << d.label << endl;
787 return out;
788 }
789 int main( )
790 {
791 Derived d1;
792 Derived d2(d1);
793 return 0;
794 }
http://blog.csdn.net/zhaori/article/details/1700356
时间： 2024-08-08 05:34:47