将指针传递给指针数组

Question

I have a test function that takes an array as an argument. And I have an array of pointers. Can someone explain why I need to deference the pointer to an array of pointers when I pass it?

void test(States a[]){

    cout << a[0].name << endl;
    cout << a[1].name << endl;
}

Calling test() :

States *pStates[MAX_STATES];
test(*pStates); //Or test(pStates[0])
                //Can't do test(pStates);

Answer 1

You won't need to dereference if the arguments of test function expect so

void test(States *a[]);

But in your case, clearly the argument type is States [] , so you need to pass a pointer.

You may want to consider rewriting test function as:

void test(States *a[]){
    cout << a[0]->name << endl;
    cout << a[1]->name << endl;
}

Answer 2

Use this instead:

void test(States* a[]){

    cout << a[0]->name << endl;
    cout << a[1]->name << endl;
}

And you won't need to dereference it...

Answer 3

The declaration of pStates declares an array of pointers. Not a pointer to an array. However the function void test(States a[]); expects an array of objects ( States objects).

You can't just cast one to the other.

#include <iostream>

typedef struct {
    int name;
} States; //Surely this should be called State (not plural)

const size_t MAX_STATES=2;


void test(States a[]){
    std::cout << a[0].name << std::endl;
    std::cout << a[1].name << std::endl;
}

int main() {

    States lFirst;
    States lSecond;
    lFirst.name=1;
    lSecond.name=7;


    //Here's what you had. 
    States*pStates[MAX_STATES];

    //Now initialise it to point to some valid objects.
    pStates[0]=&lFirst;
    pStates[1]=&lSecond;

    //Here's what you need to do.
    States lTempStates[]={*pStates[0],*pStates[1]};

    test(lTempStates); 
    return EXIT_SUCCESS;
}

Please see here https://stackoverflow.com/help/mcve