工厂模式--C语言实现

工厂模式，其实就是C++中的类的继承，只不过用C语言中的函数指针来实现了。

假设现在的需求是公司生产一系列产品，包括椅子，床等，要求先生产产品，然后将生产的产品销售出去。将来可能要增加新的产品，不希望修改现有的核心代码流程，满足开闭原则。

#include 
#include 
#include 

typedef struct PRO_STR
{
    void (*produce)(struct PRO_STR *pthis);
    void (*sell)(struct PRO_STR **pthis);
} PRO_STR, *pPRO_STR;


// 实现两个接口
void produceProduct(PRO_STR *pthis) {
    if (pthis == NULL) return;
    pthis->produce(pthis);
}

void sellProduct(PRO_STR **pthis) {
    if (pthis == NULL || *pthis == NULL) return;

    (*pthis)->sell(pthis);
    free(*pthis);
    *pthis = NULL;
}


pPRO_STR createChair();
pPRO_STR createBed();

// 工厂创建接口
pPRO_STR factoryCreate(char *strName) {

    if (0 == strcasecmp("CHAIR", strName)) {
        return createChair();
    }

    if (0 == strcasecmp("BED", strName)) {
        return createBed();
    }
}

// 子类接口实现
void produceChair(PRO_STR *pthis) {
    printf("produce a chairn");
}

void sellChair(PRO_STR **pthis) {
    printf("sell a chairn");
}

pPRO_STR createChair() {
    pPRO_STR pthis = (pPRO_STR)malloc(sizeof(PRO_STR));
    if (pthis == NULL) return NULL;

    pthis->produce = produceChair;
    pthis->sell = sellChair;

    return pthis;
}

void produceBed(PRO_STR *pthis) {
    printf("produce a bedn");
}

void sellBed(PRO_STR **pthis) {
    printf("sell a bedn");
}

pPRO_STR createBed() {
    pPRO_STR pthis = (pPRO_STR)malloc(sizeof(PRO_STR));
    if (pthis == NULL) return NULL;

    pthis->produce = produceBed;
    pthis->sell = sellBed;

    return pthis;
}

int main() {

    pPRO_STR chair = factoryCreate("CHAIR");
    produceProduct(chair);
    sellProduct(&chair);

    pPRO_STR bed = factoryCreate("BED");
    produceProduct(bed);
    sellProduct(&bed);

    return 0;
}

新的需求，每个产品有自己的属性。这时需要对外提供每个产品类别的属性结构体。

#include 
#include 
#include 

typedef struct PRO_STR
{
    void (*produce)(struct PRO_STR *pthis);
    void (*sell)(struct PRO_STR **pthis);
    void (*print)(struct PRO_STR *pthis);
    void *attr;
} PRO_STR, *pPRO_STR;


// 实现两个接口
void produceProduct(PRO_STR *pthis) {
    if (pthis == NULL) return;
    pthis->produce(pthis);
}

void sellProduct(PRO_STR **pthis) {
    if (pthis == NULL || *pthis == NULL) return;

    (*pthis)->sell(pthis);
    free(*pthis);
    *pthis = NULL;
}

void printProduct(PRO_STR *pthis) {
    if (pthis == NULL) return;
    pthis->print(pthis);
}

pPRO_STR createChair(void *attr);
pPRO_STR createBed(void *attr);

// 工厂创建接口
pPRO_STR factoryCreate(char *strName, void *attr) {

    if (0 == strcasecmp("CHAIR", strName)) {
        return createChair(attr);
    }

    if (0 == strcasecmp("BED", strName)) {
        return createBed(attr);
    }
}

// 子类接口实现
typedef struct CHAIR
{
    int heavyAbility;
    int legs;
} CHAIR;

void produceChair(PRO_STR *pthis) {
    printf("produce a chairn");
}

void sellChair(PRO_STR **pthis) {
    printf("sell a chairn");
}

void printChair(PRO_STR *pthis) {
    if (NULL == pthis) return;

    CHAIR *pChair = (CHAIR *)(pthis->attr);
    printf("heavy %d legs %d n", pChair->heavyAbility, pChair->legs);
}

pPRO_STR createChair(void *attr) {
    pPRO_STR pthis = (pPRO_STR)malloc(sizeof(PRO_STR));
    if (pthis == NULL) return NULL;

    pthis->attr = (CHAIR *)malloc(sizeof(CHAIR));
    if (NULL == pthis->attr) return NULL;

    pthis->produce = produceChair;
    pthis->sell = sellChair;
    pthis->print = printChair;
    memcpy(pthis->attr, attr, sizeof(CHAIR));

    return pthis;
}

typedef struct BED
{
    int big;
    int height;
    int lenth;
} BED;

void produceBed(PRO_STR *pthis) {
    printf("produce a bedn");
}

void sellBed(PRO_STR **pthis) {
    printf("sell a bedn");
}

void printBed(PRO_STR *pthis) {
    if (NULL == pthis) return;

    BED *pBed = (BED *)(pthis->attr);
    printf("big %d height %d length %d n", pBed->big, pBed->height, pBed->lenth);
}

pPRO_STR createBed(void *attr) {
    pPRO_STR pthis = (pPRO_STR)malloc(sizeof(PRO_STR));
    if (pthis == NULL) return NULL;

    pthis->attr = (BED *)malloc(sizeof(BED));
    if (NULL == pthis->attr) return NULL;

    pthis->produce = produceBed;
    pthis->sell = sellBed;
    pthis->print = printBed;

    memcpy(pthis->attr, attr, sizeof(BED));

    return pthis;
}

int main() {
    CHAIR chairAttr = {100,4};
    pPRO_STR chair = factoryCreate("CHAIR", &chairAttr);
    produceProduct(chair);
    printProduct(chair);
    sellProduct(&chair);

    BED bedAttr = {10, 10, 7};
    pPRO_STR bed = factoryCreate("BED", &bedAttr);
    produceProduct(bed);
    printProduct(bed);
    sellProduct(&bed);

    return 0;
}

编译执行

parallels@ubuntu-linux-20-04-desktop:~/leecode2/marco$ ./a.out 
produce a chair
heavy 100 legs 4 
sell a chair
produce a bed
big 10 height 10 length 7 
sell a bed