如何让我的程序接受指针？

Question

I am trying to make my program accept pointers as part of a requirement to deallocate the heap space and kill the pointer. My program runs fine without the adjustments I attempted to make to accept pointers. I'm getting the following error

lab.cpp: In function 'int main()':
lab.cpp:21:19: error: request for member 'unit' in 'shipment', which is of pointer type 'cargo*'
(maybe you meant to use '->' ?)
21 |    input(shipment.unit);
  |                   ^~~~
lab.cpp:22:20: error: request for member 'unit' in 'shipment', which is of pointer type 'cargo*'   
(maybe you meant to use '->' ?)
22 |    output(shipment.unit);
  |                    ^~~~

Here is my program without the adjustments, really simple but it works. All it's doing is taking input and outputting it, just setting it up for now as my assignment is to collect data from user and output it while deallocating the heapspace

#include <iostream>
#include <string>
using namespace std;
struct cargo{
   string unit;
   string unitID;
   int airCraft;
   int weight;
   string destination;
};
void input(cargo shipment){
   cout << "Is it a pallet or a container?" << endl; 
   getline(cin, shipment.unit);
}
void output(cargo shipment){
   cout << shipment.unit << endl;
}

int main() {
   cargo shipment;
   input(shipment);
   output(shipment);
   return 0;
}

Here is my program with my adjustments

#include <iostream>
#include <string>
using namespace std;
struct cargo{
   string unit;
   string unitID;
   int airCraft;
    int weight;
    string destination;
 };
 void input(cargo *shipment){
    cout << "Is it a pallet or a container?" << endl; 
    getline(cin, shipment.unit);
 }
 void output(cargo *shipment){
    cout << shipment.unit << endl;
 }

 int main() {
    cargo *shipment = new cargo;
    input(shipment.unit);
    output(shipment.unit);
    delete shipment;
    shipment = nullptr;
    return 0;
 }

Answer 1

When accessing an pointer's members, you need to use the arrow ( -> ) operator. But your methods input and output takes the cargo pointer. After accessing its member, you'll return the member, not the pointer. So by doing shipment.unit , your returning a string.

To fix it, lest just pass in the pointer.

void input(cargo *shipment){
    cout << "Is it a pallet or a container?" << endl; 
    getline(cin, shipment->unit);
 }
 void output(cargo *shipment){
    cout << shipment->unit << endl;
}

...

input(shipment);
output(shipment);

Additional: After deleting the shipment , assigning it a nullptr is useless. Your not gonna use it anyway.