OOP in C - Before GObject (Chinese Version)
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This document discusses object-oriented programming concepts in C, including constructors. It explains how constructors work in C++, and how they can be simulated in C by using naming conventions and manually initializing parent and member values. The document concludes that for more complex inheritance hierarchies, it is better to use an object system like GObject that handles constructor execution order and initialization automatically.
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OOP in C - Before GObject (Chinese Version)
- 1. OOP in C Before GObject [email_address] elpam@Taiwan, Taipei, 2008
- 2. LICENSE 本投影片授權方式為： 姓名標示─非商業性─相同方式分享 3.0 台灣版
- 4. About This Slides All example was build by GCC-4.1.3
- 5. GLIB-1.2.10
- 6. GMAKE-3.81
- 7. Agenda Constructor Review in C++
- 9. C++ Language Review Constructor parent's constructor
- 11. initial member function (x)
- 12. do something class Dog: public Animal{ private : string name; public: Dog(); }; Dog::Dog( const string n) : Animal() /*(1)*/ , name(n) /*(2)*/ { /* (4) */ cout << '' 汪汪 '' << endl; }
- 13. C++ Constructor Which one? cba
- 14. abc /* 3-1.cpp */ class A{ public: A(){printf( “a” );}; }; class B: public A{ public: B(){printf( “b” );}; }; class C: public B{ public: C(){printf( “c” );}; }; C* c = new C;
- 15. C++ Constructor (cont') Answer: abc Why parent's constructor execute first ? 在child的Constructor之中可能會Access到Parent的member value (及 member function)
- 16. C++ Default Constructor Which one? abc
- 17. abC
- 18. ABC /* 3-2.cpp */ class A{ public: A(){printf( “a” );}; A( int ){printf( “A” );}; }; class B: public A{ public: B(){printf( “b” );}; B( int ){printf( “B” );}; }; class C: public B{ public: C(){printf( “c” );}; C( int ){printf( “C” );}; }; C* c = new C(1);
- 19. C++ Default Constructor (cont') Answer: abC 在沒有指定的情況之下Compiler會使用預設的Constructor 也就是沒有參數的那一個 如果將A:A()拿掉的話會發生什麼事? /* 3-2.cpp */ class A{ public: A(){printf( “a” );}; A( int ){printf( “A” );}; }; class B: public A{ public: B(){printf( “b” );}; B( int ){printf( “B” );}; }; class C: public B{ public: C(){printf( “c” );}; C( int ){printf( “C” );}; }; C* c = new C(1);
- 20. Write Constructor Accurately constructor( Value ) : parent's constructor , member value initialize { /* do something */ } /* 3-3.hpp */ class A{ public: A(){ va = 0 ; }; A( int v){ va = v; }; private: int va; }; class B: public A{ public: B(); B( int ); private: int vb; }; /* ex3.cpp */ B::B() : A() , vb( 0 ) { printf( '' hello this is B() \n'' ); B::B( int v) : A( v ) /* !! */ , vb( v ) { printf( '' hello this is B(int) \n'' );
- 21. Constructor 該做的事情 parent's constructor
- 23. do something constructor( Value ) : parent's constructor , member value initialize { /* do something */ }
- 24. From C++ to C
- 25. Constructor in C we use blahblah_new to replace malloc 命名方式並沒有語法上的限制 struct A{ int a; int b; }; struct A* A_new() { struct A* ret = malloc( sizeof (A) ); ret -> a = 0; ret -> a = 1; return ret; }
- 26. Constructor in C (cont') Constructor parent's constructor
- 28. do something struct A{ int a; }; struct B{ struct A parent; int a; }; struct A* A_new() { struct A* ret = malloc( sizeof (A) ); ret -> a = 0; return ret; } struct B* B_new() { struct B* ret = malloc( sizeof (B) ); ret -> parent -> a = 0; /* ???? */ ret -> b = 0; return ret; }
- 29. Constructor's Properties 不用宣告即有Virtual的屬性 執行繼承關係裡最下層的Constructor Child的Constructor執行之前，Parent的Constructor 應該要先被執行 上面的範例需要手動的檢查，才能正確的執行parent's constructor
- 30. Constructor's Properties (cont') Drawback: Parent's constructor can't be reused! You need to rewrite the code what parent do Initialize parent's member value
- 31. Initialize parent's member function!?
- 32. ............. Yes, what we think is the same. Boring jobs should be prevent. Stupid codes should be removed. Or we'll always find out stupid bug. Let's why we use Gobject to do this
- 36. V-Table Actually, above concept is coming from the implementation of V-Table (Virtual-Function-Table, Dispatch Table).
- 37. You can find out more information via reading OO Language's compiler implementation or some JIT interpreter's implementation. http://en.wikipedia.org/wiki/Vtable