简单工厂模式（C语言实现）

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工厂模式属于创建型模式，大致可以分为三类，简单工厂模式、工厂方法模式、抽象工厂模式。

一. 简单工厂模式

简单工厂模式，它的主要特点是需要在工厂类中做判断，从而创造相应的产品。当增加新的产品时，就需要修改工厂类。举个例子，有一家电子产品生产厂家，它只有一个工厂，能够生产两种型号的产品，A 和 B。可以想像一下，A是电吹风，B是电风扇。客户需要什么样的吹风类产品，一定要显示地告诉生产工厂。

代码实现：

abstractClass.h

#ifndef ABSTRACTCLASS_H#define ABSTRACTCLASS_H#include <stdlib.h>#include <stdarg.h>typedef struct {    size_t size;    void* (*ctor)(void *_self, va_list *params);    void* (*dtor)(void *_self);} AbstractClass;#endif

factory.h

#ifndef FACTORY_H#define FACTORY_H#include <stdlib.h>#include <stdarg.h>typedef enum {    PRODUCT_A,    PRODUCT_B} PRODUCT_TYPE;typedef struct {    size_t size;    void* (*ctor)(void *_self, va_list *params);    void* (*dtor)(void *_self);    void* (*createProduct)(const void *_self, PRODUCT_TYPE productType);} _Factory;extern const void *Factory;#endif

factory.c

#include "new.h"#include "factory.h"#include "productA.h"#include "productB.h"#include <stdlib.h>#include <stdarg.h>static void *factoryCtor(void *_self, va_list *params) {    _Factory *self = _self;    return self;}static void *factoryDtor(void *_self) {    _Factory *self = _self;    return self;}static void* factoryCreateProduct(const void *_self, PRODUCT_TYPE productType) {    void *product = NULL;        switch(productType) {        case PRODUCT_A:            product = New(ProductA);            break;        case PRODUCT_B:            product = New(ProductB);            break;        default:            break;    }    return product;}static const _Factory _factory = {    sizeof(_Factory),    factoryCtor,    factoryDtor,    factoryCreateProduct};const void *Factory = &_factory;

product.h

#ifndef PRODUCT_H#define PRODUCT_H#include <stdlib.h>#include <stdarg.h>typedef struct {    size_t size;    void* (*ctor)(void *_self, va_list *params);    void* (*dtor)(void *_self);    void (*show)(const void *_self);} Product;#endif

productA.h

#ifndef PRODUCTA_H#define PRODUCTA_Htypedef struct {    const void *_;} _ProductA;extern const void *ProductA;#endif

productA.c

#include "product.h"#include "productA.h"#include <stdarg.h>#include <stdio.h>static void *productACtor(void *_self, va_list *params) {    _ProductA *self = _self;    return self;}static void *productADtor(void *_self) {    _ProductA *self = _self;    return self;}static void productAShow(const void *_self) {    (void)_self;    fprintf(stdout, "Product A\n");}static const Product _product = {    sizeof(_ProductA),    productACtor,    productADtor,    productAShow};const void *ProductA = &_product;

productB.h

#ifndef PRODUCTB_H#define PRODUCTB_Htypedef struct {    const void *_;} _ProductB;extern const void *ProductB;#endif

productB.c

#include "product.h"#include "productB.h"#include <stdarg.h>#include <stdio.h>#include <stdlib.h>static void *productBCtor(void *_self, va_list *params) {    _ProductB *self = _self;    return self;}static void *productBDtor(void *_self) {    _ProductB *self = _self;    return self;}static void productBShow(const void *_self) {    (void)_self;    fprintf(stdout, "Product B\n");}static const Product _product = {    sizeof(_ProductB),    productBCtor,    productBDtor,        productBShow};const void *ProductB = &_product;

new.h

#ifndef NEW_H#define NEW_Hvoid *New(const void *_class, ...);void Delete(void *_class);void *CreateProduct(const void *_factory, int productType);void Show(const void *product);#endif

new.c

#include "new.h"#include "abstractClass.h"#include "factory.h"#include "product.h"#include <stdarg.h>#include <stdlib.h>#include <assert.h>#include <stdio.h>void *New(const void *_class, ...) {    const AbstractClass *class = _class;    void *p = calloc(1, class->size);    assert(p);    *(const AbstractClass **)p = class;        if (class->ctor) {        va_list params;        va_start(params, _class);        p = class->ctor(p, ¶ms);        va_end(params);    }    return p;}void Delete(void *_class) {    const AbstractClass **class = _class;    if (_class && *class && (*class)->dtor) {        _class = (*class)->dtor(_class);    }    free(_class);}void *CreateProduct(const void *_factory, int productType) {    return ((const _Factory*)Factory)->createProduct(_factory, productType);}void Show(const void *_product) {    const Product * const *product = _product;    if (_product && *product && (*product)->show) {            (*product)->show(_product);    }}

main.c

#include "new.h"#include "factory.h"int main(int argc, char *argv[]) {    void *fac = New(Factory);    void *pro1 = CreateProduct(fac, PRODUCT_A);    void *pro2 = CreateProduct(fac, PRODUCT_B);                                               Show(pro1);    Show(pro2);    Delete(fac);    Delete(pro1);    Delete(pro2);        return 0;}

图片来源：http://blog.csdn.net/hmsiwtv/article/details/9627109

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