本文探討如何在C語言中模擬面向?qū)ο缶幊讨械慕涌诟拍?。我們將以計算車輛價格為例，分別用Java和C語言實現(xiàn)，對比兩種語言的差異，并展示如何在C中實現(xiàn)接口的基本功能。

Java實現(xiàn)：

Java中，接口使用interface關(guān)鍵字定義，類通過implements關(guān)鍵字實現(xiàn)接口。示例代碼如下：

interface Vehicle {
    int price();
}

class Car implements Vehicle {
    private final int speed;

    public Car(int speed) {
        this.speed = speed;
    }

    @Override
    public int price() {
        return speed * 60;
    }
}

class Motorcycle implements Vehicle {
    private final int cc;

    public Motorcycle(int cc) {
        this.cc = cc;
    }

    @Override
    public int price() {
        return cc * 10;
    }
}

public class Main {
    public static void printVehiclePrice(Vehicle vehicle) {
        System.out.println("$"   vehicle.price()   ".00");
    }

    public static void main(String[] args) {
        Car car = new Car(120);
        Motorcycle motorcycle = new Motorcycle(1000);

        printVehiclePrice(car);
        printVehiclePrice(motorcycle);
    }
}

C語言實現(xiàn)：

C語言沒有直接的接口機制。我們可以通過枚舉類型、結(jié)構(gòu)體和函數(shù)指針來模擬接口的行為。

首先定義枚舉類型表示車輛類型：

typedef enum { VEHICLE_CAR, VEHICLE_MOTORCYCLE } VehicleType;

然后定義車輛結(jié)構(gòu)體，包含類型信息和函數(shù)指針：

typedef struct {
    VehicleType type;
    int (*price)(void*); // 函數(shù)指針，指向價格計算函數(shù)
} Vehicle;

接下來，實現(xiàn)汽車和摩托車結(jié)構(gòu)體：

typedef struct {
    VehicleType type;
    int speed;
} Car;

typedef struct {
    VehicleType type;
    int cc;
} Motorcycle;

相應(yīng)的初始化和價格計算函數(shù)：

Car* car_init(int speed) {
    Car* car = malloc(sizeof(Car));
    car->type = VEHICLE_CAR;
    car->speed = speed;
    return car;
}

int car_price(void* car) {
    return ((Car*)car)->speed * 60;
}

Motorcycle* motorcycle_init(int cc) {
    Motorcycle* motorcycle = malloc(sizeof(Motorcycle));
    motorcycle->type = VEHICLE_MOTORCYCLE;
    motorcycle->cc = cc;
    return motorcycle;
}

int motorcycle_price(void* motorcycle) {
    return ((Motorcycle*)motorcycle)->cc * 10;
}

最后，實現(xiàn)vehicle_price函數(shù)，根據(jù)車輛類型調(diào)用不同的價格計算函數(shù)：

int vehicle_price(Vehicle* vehicle) {
    switch (vehicle->type) {
        case VEHICLE_CAR:
            return car_price((Car*)vehicle);
        case VEHICLE_MOTORCYCLE:
            return motorcycle_price((Motorcycle*)vehicle);
        default:
            return 0;
    }
}

void print_vehicle_price(Vehicle* vehicle) {
    printf("$%d.00\n", vehicle_price(vehicle));
}

int main() {
    Vehicle car_v = {VEHICLE_CAR, car_price};
    ((Car*)&car_v)->speed = 120; // 強制類型轉(zhuǎn)換

    Vehicle motorcycle_v = {VEHICLE_MOTORCYCLE, motorcycle_price};
    ((Motorcycle*)&motorcycle_v)->cc = 1000; // 強制類型轉(zhuǎn)換


    print_vehicle_price(&car_v);
    print_vehicle_price(&motorcycle_v);

    free((Car*)&car_v);
    free((Motorcycle*)&motorcycle_v);
    return 0;
}

這種C語言的實現(xiàn)模擬了接口的行為，但需要手動管理內(nèi)存和類型轉(zhuǎn)換，相比Java的接口機制更加復(fù)雜。 這種方法在處理復(fù)雜數(shù)據(jù)結(jié)構(gòu)，例如抽象語法樹（AST）時，可以提高代碼的可維護性和可讀性。

以上是C語言中的面向?qū)ο螅繌念^開始實現(xiàn)接口的詳細內(nèi)容。更多信息請關(guān)注PHP中文網(wǎng)其他相關(guān)文章！