如何用C编写面向对象的代码?
用C编写面向对象代码的方法有哪些?特别是在多态性方面如何用C编写面向对象的代码?,c,oop,object,C,Oop,Object,用C编写面向对象代码的方法有哪些?特别是在多态性方面 另请参阅此堆栈溢出问题。我已经看到它完成了。我不推荐。C++最初是以C代码作为中间步骤的预处理器开始的。 基本上,您最终要做的是为存储函数引用的所有方法创建一个分派表。派生类需要复制此分派表并替换要重写的条目,如果新“方法”要调用基方法,则必须调用原始方法。最后,你改写C++。 你可以用函数指针来伪造它,事实上,我认为编译C++程序到C.中是有可能的。 然而,在一种语言上强制一个范例很少有意义,而不是选择一种使用范例的语言。 < p>既然你
另请参阅此堆栈溢出问题。我已经看到它完成了。我不推荐。C++最初是以C代码作为中间步骤的预处理器开始的。
基本上,您最终要做的是为存储函数引用的所有方法创建一个分派表。派生类需要复制此分派表并替换要重写的条目,如果新“方法”要调用基方法,则必须调用原始方法。最后,你改写C++。 你可以用函数指针来伪造它,事实上,我认为编译C++程序到C.</P>中是有可能的。
然而,在一种语言上强制一个范例很少有意义,而不是选择一种使用范例的语言。 < p>既然你在谈论多态性,那么是的,你可以,我们在C++出现之前几年就做过这样的事情。 基本上,您可以使用
struct
来保存数据和函数指针列表,以指向该数据的相关函数
因此,在通信类中,您将有一个open、read、write和close调用,该调用将作为结构中的四个函数指针进行维护,与对象的数据一起,类似于:
typedef struct {
int (*open)(void *self, char *fspec);
int (*close)(void *self);
int (*read)(void *self, void *buff, size_t max_sz, size_t *p_act_sz);
int (*write)(void *self, void *buff, size_t max_sz, size_t *p_act_sz);
// And data goes here.
} tCommClass;
tCommClass commRs232;
commRs232.open = &rs232Open;
: :
commRs232.write = &rs232Write;
tCommClass commTcp;
commTcp.open = &tcpOpen;
: :
commTcp.write = &tcpWrite;
当然,上面的代码段实际上是在一个“构造函数”中,比如rs232Init()
当您从该类“继承”时,只需更改指针以指向您自己的函数。每个调用这些函数的人都会通过函数指针来实现,从而为您提供多态性:
int stat = (commTcp.open)(commTcp, "bigiron.box.com:5000");
有点像手动vtable
您甚至可以通过将指针设置为null来实现虚拟类,行为将与C++(运行时的内核转储而不是编译时的错误)略有不同。
下面是一段示例代码来演示它。首先是顶级班级结构:
#include <stdio.h>
// The top-level class.
typedef struct sCommClass {
int (*open)(struct sCommClass *self, char *fspec);
} tCommClass;
还有HTTP协议:
// Function for the HTTP 'class'.
static int httpOpen (tCommClass *http, char *fspec) {
printf ("Opening HTTP: %s\n", fspec);
return 0;
}
static int httpInit (tCommClass *http) {
http->open = &httpOpen;
return 0;
}
最后是一个测试程序,以显示其实际效果:
// Test program.
int main (void) {
int status;
tCommClass commTcp, commHttp;
// Same 'base' class but initialised to different sub-classes.
tcpInit (&commTcp);
httpInit (&commHttp);
// Called in exactly the same manner.
status = (commTcp.open)(&commTcp, "bigiron.box.com:5000");
status = (commHttp.open)(&commHttp, "http://www.microsoft.com");
return 0;
}
这将产生以下输出:
Opening TCP: bigiron.box.com:5000
Opening HTTP: http://www.microsoft.com
因此,您可以看到,根据子类的不同,调用了不同的函数。面向对象C是可以完成的,我在韩国的生产中见过这种类型的代码,这是我多年来见过的最可怕的怪物(就像我去年(2007年)看到的代码)。
所以,是的,这是可以做到的,是的,人们以前做过,甚至在今天这个时代仍然这样做。但是我建议C++或Objul-C,它们都是C语言生成的,目的是提供面向对象的不同范式。p> 是的。事实上,Axel Schreiner免费提供了“ANSI-C面向对象编程”,涵盖了这个主题 在Jim Larson 1996年的演讲中,这里有一个使用C进行继承的例子:。确定这是可能的。这就是所有的和基于的框架所做的。是的,你可以。人们在C++之前或是在现场出现了面向对象的C语言。C++和Objul-C都试图在C中使用一些面向对象概念,并将它们形式化为语言的一部分。 下面是一个非常简单的程序,它展示了如何进行类似于/是方法调用的操作(有更好的方法可以做到这一点。这只是证明语言支持这些概念):
#包括
结构foobarbaz{
int-one;
int-2;
int三;
int(*示例方法)(int,int);
};
int addTwoNumber(int a,int b){
返回a+b;
}
int main()
{
//定义函数指针
int(*pointerToFunction)(int,int)=添加两个数字;
//让我们确保可以调用指针
int test=(*指针函数)(12,12);
printf(“测试:%u\n”,测试);
//现在,定义结构的一个实例
//并添加一些默认值。
结构foobarbaz fbb;
fbb.one=1;
fbb.2=2;
fbb.3=3;
//现在添加一个“方法”
fbb.exampleMethod=addTwoNumber;
//尝试调用该方法
int test2=fbb.exampleMethod(13,36);
printf(“test2:%u\n”,test2);
printf(“\nDone\n”);
返回0;
}
一个关于动物和狗的简单例子:您镜像了C++的vtable机制(基本上是无论如何)。您还可以分离分配和实例化(Animal_Alloc,Animal_New),这样我们就不会多次调用malloc()。我们还必须显式地传递这个指针
如果你要做非虚拟函数,那就太琐碎了。您不需要将它们添加到vtable,静态函数不需要这个
指针。多重继承通常需要多个vTable来解决歧义
此外,您应该能够使用setjmp/longjmp来进行异常处理
struct Animal_Vtable{
typedef void (*Walk_Fun)(struct Animal *a_This);
typedef struct Animal * (*Dtor_Fun)(struct Animal *a_This);
Walk_Fun Walk;
Dtor_Fun Dtor;
};
struct Animal{
Animal_Vtable vtable;
char *Name;
};
struct Dog{
Animal_Vtable vtable;
char *Name; // Mirror member variables for easy access
char *Type;
};
void Animal_Walk(struct Animal *a_This){
printf("Animal (%s) walking\n", a_This->Name);
}
struct Animal* Animal_Dtor(struct Animal *a_This){
printf("animal::dtor\n");
return a_This;
}
Animal *Animal_Alloc(){
return (Animal*)malloc(sizeof(Animal));
}
Animal *Animal_New(Animal *a_Animal){
a_Animal->vtable.Walk = Animal_Walk;
a_Animal->vtable.Dtor = Animal_Dtor;
a_Animal->Name = "Anonymous";
return a_Animal;
}
void Animal_Free(Animal *a_This){
a_This->vtable.Dtor(a_This);
free(a_This);
}
void Dog_Walk(struct Dog *a_This){
printf("Dog walking %s (%s)\n", a_This->Type, a_This->Name);
}
Dog* Dog_Dtor(struct Dog *a_This){
// Explicit call to parent destructor
Animal_Dtor((Animal*)a_This);
printf("dog::dtor\n");
return a_This;
}
Dog *Dog_Alloc(){
return (Dog*)malloc(sizeof(Dog));
}
Dog *Dog_New(Dog *a_Dog){
// Explict call to parent constructor
Animal_New((Animal*)a_Dog);
a_Dog->Type = "Dog type";
a_Dog->vtable.Walk = (Animal_Vtable::Walk_Fun) Dog_Walk;
a_Dog->vtable.Dtor = (Animal_Vtable::Dtor_Fun) Dog_Dtor;
return a_Dog;
}
int main(int argc, char **argv){
/*
Base class:
Animal *a_Animal = Animal_New(Animal_Alloc());
*/
Animal *a_Animal = (Animal*)Dog_New(Dog_Alloc());
a_Animal->vtable.Walk(a_Animal);
Animal_Free(a_Animal);
}
这是在C++编译器上测试的,但是应该很容易使它在C编译器上工作。
当然,它并不像使用内置支持的语言那么漂亮。我甚至写过“面向对象的汇编程序”。
如果您确信OOP方法对于您试图解决的问题是优越的,那么您为什么要尝试使用非OOP语言来解决它?看来你用错工具了。使用C++或其他面向对象的C语言。
如果你问这个问题是因为你开始在一个已经存在的用C编写的大型项目上进行编码,那么你不应该试图将你自己(或其他任何人)的OOP范例强制到项目的基础设施中。遵循项目中已有的指导原则。一般来说,干净的API和独立的库和模块将大大有助于实现干净的OOP-ish设计
如果在所有这些之后,您真的开始做OOPC,请阅读(PDF)。请检查。它是C中的OO和w的一个实现
#include<stdio.h>
struct foobarbaz{
int one;
int two;
int three;
int (*exampleMethod)(int, int);
};
int addTwoNumbers(int a, int b){
return a+b;
}
int main()
{
// Define the function pointer
int (*pointerToFunction)(int, int) = addTwoNumbers;
// Let's make sure we can call the pointer
int test = (*pointerToFunction)(12,12);
printf ("test: %u \n", test);
// Now, define an instance of our struct
// and add some default values.
struct foobarbaz fbb;
fbb.one = 1;
fbb.two = 2;
fbb.three = 3;
// Now add a "method"
fbb.exampleMethod = addTwoNumbers;
// Try calling the method
int test2 = fbb.exampleMethod(13,36);
printf ("test2: %u \n", test2);
printf("\nDone\n");
return 0;
}
struct Animal_Vtable{
typedef void (*Walk_Fun)(struct Animal *a_This);
typedef struct Animal * (*Dtor_Fun)(struct Animal *a_This);
Walk_Fun Walk;
Dtor_Fun Dtor;
};
struct Animal{
Animal_Vtable vtable;
char *Name;
};
struct Dog{
Animal_Vtable vtable;
char *Name; // Mirror member variables for easy access
char *Type;
};
void Animal_Walk(struct Animal *a_This){
printf("Animal (%s) walking\n", a_This->Name);
}
struct Animal* Animal_Dtor(struct Animal *a_This){
printf("animal::dtor\n");
return a_This;
}
Animal *Animal_Alloc(){
return (Animal*)malloc(sizeof(Animal));
}
Animal *Animal_New(Animal *a_Animal){
a_Animal->vtable.Walk = Animal_Walk;
a_Animal->vtable.Dtor = Animal_Dtor;
a_Animal->Name = "Anonymous";
return a_Animal;
}
void Animal_Free(Animal *a_This){
a_This->vtable.Dtor(a_This);
free(a_This);
}
void Dog_Walk(struct Dog *a_This){
printf("Dog walking %s (%s)\n", a_This->Type, a_This->Name);
}
Dog* Dog_Dtor(struct Dog *a_This){
// Explicit call to parent destructor
Animal_Dtor((Animal*)a_This);
printf("dog::dtor\n");
return a_This;
}
Dog *Dog_Alloc(){
return (Dog*)malloc(sizeof(Dog));
}
Dog *Dog_New(Dog *a_Dog){
// Explict call to parent constructor
Animal_New((Animal*)a_Dog);
a_Dog->Type = "Dog type";
a_Dog->vtable.Walk = (Animal_Vtable::Walk_Fun) Dog_Walk;
a_Dog->vtable.Dtor = (Animal_Vtable::Dtor_Fun) Dog_Dtor;
return a_Dog;
}
int main(int argc, char **argv){
/*
Base class:
Animal *a_Animal = Animal_New(Animal_Alloc());
*/
Animal *a_Animal = (Animal*)Dog_New(Dog_Alloc());
a_Animal->vtable.Walk(a_Animal);
Animal_Free(a_Animal);
}
#ifndef FOO_H_
#define FOO_H_
...
typedef struct FOO_type FOO_type; /* That's all the rest of the program knows about FOO */
/* Declaration of accessors, functions */
FOO_type *FOO_new(void);
void FOO_free(FOO_type *this);
...
void FOO_dosomething(FOO_type *this, param ...):
char *FOO_getName(FOO_type *this, etc);
#endif
#include <stdlib.h>
...
#include "FOO.h"
struct FOO_type {
whatever...
};
FOO_type *FOO_new(void)
{
FOO_type *this = calloc(1, sizeof (FOO_type));
...
FOO_dosomething(this, );
return this;
}
stack_push(thing *)
stack::push(thing *)
class stack {
public:
stack();
void push(thing *);
thing * pop();
static int this_is_here_as_an_example_only;
private:
...
};
struct stack {
struct stack_type * my_type;
// Put the stuff that you put after private: here
};
struct stack_type {
void (* construct)(struct stack * this); // This takes uninitialized memory
struct stack * (* operator_new)(); // This allocates a new struct, passes it to construct, and then returns it
void (*push)(struct stack * this, thing * t); // Pushing t onto this stack
thing * (*pop)(struct stack * this); // Pops the top thing off the stack and returns it
int this_is_here_as_an_example_only;
}Stack = {
.construct = stack_construct,
.operator_new = stack_operator_new,
.push = stack_push,
.pop = stack_pop
};
// All of these functions are assumed to be defined somewhere else
struct stack * st = Stack.operator_new(); // Make a new stack
if (!st) {
// Do something about it
} else {
// You can use the stack
stack_push(st, thing0); // This is a non-virtual call
Stack.push(st, thing1); // This is like casting *st to a Stack (which it already is) and doing the push
st->my_type.push(st, thing2); // This is a virtual call
}
#include <stdio.h>
struct Node {
int somevar;
};
void print() {
printf("Hello from an object-oriented C method!");
};
struct Tree {
struct Node * NIL;
void (*FPprint)(void);
struct Node *root;
struct Node NIL_t;
} TreeA = {&TreeA.NIL_t,print};
int main()
{
struct Tree TreeB;
TreeB = TreeA;
TreeB.FPprint();
return 0;
}
#include "OOStd.h"
CLASS(Animal) {
char *name;
STATIC(Animal);
vFn talk;
};
static int Animal_load(Animal *THIS,void *name) {
THIS->name = name;
return 0;
}
ASM(Animal, Animal_load, NULL, NULL, NULL)
CLASS_EX(Cat,Animal) {
STATIC_EX(Cat, Animal);
};
static void Meow(Animal *THIS){
printf("Meow!My name is %s!\n", THIS->name);
}
static int Cat_loadSt(StAnimal *THIS, void *PARAM){
THIS->talk = (void *)Meow;
return 0;
}
ASM_EX(Cat,Animal, NULL, NULL, Cat_loadSt, NULL)
CLASS_EX(Dog,Animal){
STATIC_EX(Dog, Animal);
};
static void Woof(Animal *THIS){
printf("Woof!My name is %s!\n", THIS->name);
}
static int Dog_loadSt(StAnimal *THIS, void *PARAM) {
THIS->talk = (void *)Woof;
return 0;
}
ASM_EX(Dog, Animal, NULL, NULL, Dog_loadSt, NULL)
int main(){
Animal *animals[4000];
StAnimal *f;
int i = 0;
for (i=0; i<4000; i++)
{
if(i%2==0)
animals[i] = NEW(Dog,"Jack");
else
animals[i] = NEW(Cat,"Lily");
};
f = ST(animals[0]);
for(i=0; i<4000; ++i) {
f->talk(animals[i]);
}
for (i=0; i<4000; ++i) {
DELETE0(animals[i]);
}
return 0;
}
typedef struct _peeker
{
log_t *log;
symbols_t *sym;
scanner_t scan; // inherited instance
peek_t pk;
int trace;
void (*push) ( SELF *d, symbol_t *symbol );
short (*peek) ( SELF *d, int level );
short (*get) ( SELF *d );
int (*get_line_number) ( SELF *d );
} peeker_t, SlkToken;
#define push(self,a) (*self).push(self, a)
#define peek(self,a) (*self).peek(self, a)
#define get(self) (*self).get(self)
#define get_line_number(self) (*self).get_line_number(self)
INSTANCE_METHOD
int
(get_line_number) ( peeker_t *d )
{
return d->scan.line_number;
}
PUBLIC
void
InitializePeeker ( peeker_t *peeker,
int trace,
symbols_t *symbols,
log_t *log,
list_t *list )
{
InitializeScanner ( &peeker->scan, trace, symbols, log, list );
peeker->log = log;
peeker->sym = symbols;
peeker->pk.current = peeker->pk.buffer;
peeker->pk.count = 0;
peeker->trace = trace;
peeker->get_line_number = get_line_number;
peeker->push = push;
peeker->get = get;
peeker->peek = peek;
}
#include "triangle.h"
#include "rectangle.h"
#include "polygon.h"
#include <stdio.h>
int main()
{
Triangle tr1= CTriangle->new();
Rectangle rc1= CRectangle->new();
tr1->width= rc1->width= 3.2;
tr1->height= rc1->height= 4.1;
CPolygon->printArea((Polygon)tr1);
printf("\n");
CPolygon->printArea((Polygon)rc1);
}
/*output:
6.56
13.12
*/
//private_class.h
struct private_class;
extern struct private_class * new_private_class();
extern int ret_a_value(struct private_class *, int a, int b);
extern void delete_private_class(struct private_class *);
void (*late_bind_function)(struct private_class *p);
//private_class.c
struct inherited_class_1;
struct inherited_class_2;
struct private_class {
int a;
int b;
struct inherited_class_1 *p1;
struct inherited_class_2 *p2;
};
struct inherited_class_1 * new_inherited_class_1();
struct inherited_class_2 * new_inherited_class_2();
struct private_class * new_private_class() {
struct private_class *p;
p = (struct private_class*) malloc(sizeof(struct private_class));
p->a = 0;
p->b = 0;
p->p1 = new_inherited_class_1();
p->p2 = new_inherited_class_2();
return p;
}
int ret_a_value(struct private_class *p, int a, int b) {
return p->a + p->b + a + b;
}
void delete_private_class(struct private_class *p) {
//release any resources
//call delete methods for inherited classes
free(p);
}
//main.c
struct private_class *p;
p = new_private_class();
late_bind_function = &implementation_function;
delete_private_class(p);