如何将结构传递给函数

Question

Could anyone tell me explain, how to pass struct into a function? I've tried to put my sorting into a function, and pass my struct into it

typedef struct
{
    int weight;
    int price;
    Color color;
    Equip equip;
}Cars;

Cars automobil[5]; 

sort_cars(&automobil[NUMBER_OF_CARS]);

void sort_cars(struct Cars*automobil[NUMBER_OF_CARS]){
    int i,j;
    CarsmobilOne={};
    for(j=0; j<NUMBER_OF_CARS-1; j++)
    {
        for (i=0; i<NUMBER_OF_CARS-1; i++){
            if (automobil[i]->weight < automobil[i+1]->weight)
            {
                continue;

            }else{
                mobilOne = automobil[i];
                automobil[i] = automobil[i+1];
                automobil[i+1] = mobilOne;
            }
        }
    }

I got this error "incompatible types when assigning to type 'Cars' from type 'struct Cars*'|" I've tried to do passing the struct as people do in the Internet

Answer 1

I've tried to do passing the struct as people do in the Internet

No, you have not. You have tried to invent a new syntax for passing an array, but unfortunately it is not the way arrays are passed in C language.

In C language, arrays do decay to pointers when they are passed as parameters to functions, so people usually pass the actual length along with the array.

So you should use:

void sort_cars(Cars*automobil, int number_of_cars){
    int i,j;
    Cars mobilOne={};
    for(j=0; j<number_of_cars-1; j++)
    {
        for (i=0; i<number_of_cars-1; i++){
            if (automobil[i]->weight < automobil[i+1]->weight)
            {
                continue;

            }else{
                mobilOne = automobil[i];
                automobil[i] = automobil[i+1];
                automobil[i+1] = mobilOne;
            }
        }
    }
}

And call it:

sort_cars(automobil, 5);

Answer 2

int carsSort(const void *a, const void *b) {
    return ((Cars *) a)->weight - ((Cars *) b)->weight;
}

void sortThem(Cars autom[]) {
    qsort(autom, NC, sizeof *autom, carsSort);
}

int main() {
    Cars automobil[NC];

    // Initialiase automobil here
    sortThem(automobil);

    for (int i = 0; i < NC; ++i)
    printf("%d\n", automobil[i].weight);
}

Remember one of the many wise sayings of K&R: "When an array name is passed to a function, what is passed is the location of the beginning of the array".

Inside sortThem() "autom" is a variable whose value is the address of automobil[0].

John