C++ cannot convert 'type' to 'type*'

Question

getting this error in my code error: cannot convert 'Aircrafts' to 'Aircrafts*'

All I am trying to do is add a class record into a vector.

it is a c++ code and using -ansi -Wall -pedantic

it is bit annoying me. Hope somebody can help. Here is my code:

error is given for this line temp_aircraft = Aircrafts("Scenic", "Piper Arrow", 3, 120, 0, 0);

#include <iostream>
#include <string>
#include <stdlib.h>
#include <vector>
#include <iomanip>

using namespace std;

class Aircrafts
{
   public:
      string category;
      string aircraft;

   public: 

      Aircrafts () { 
         category = "";
         aircraft = "";         
      }

      Aircrafts (string f_cat, string airc) {
         category = f_cat;
         aircraft = airc;
      }      
}

void main()
{

   vector <Aircrafts> aircraft_list;

   Aircrafts *temp_aircraft;

   temp_aircraft = new Aircrafts;
   temp_aircraft = Aircrafts("Abc", "Xyz");
   aircraft_list.push_back(*temp_aircraft);
}

For learning more on basics like this, you might want to pick up a [good book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). — Angew is no longer proud of SO, Nov 21 '13 at 10:34

score 4 · Accepted Answer · answered Nov 21 '13 at 10:33

4

To fix the error in levels of indirection, you can replace

temp_aircraft = new Aircrafts;
temp_aircraft = Aircrafts("Abc", "Xyz");

with

temp_aircraft = new Aircrafts("Abc", "Xyz");

That's the correct syntax for calling a constructor with parameters. However, this creates a memory leak.

You do not need new there at all - you can do everything on a single line without using a temp_aircraft pointer:

aircraft_list.push_back(Aircrafts("Abc", "Xyz"));

answered Nov 21 '13 at 10:33

Sergey Kalinichenko

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And even if you _did_ use a `temp_Aircraft`, you still wouldn't need to make it a pointer: `Aircrafts temp_Aircraft{"Abc", "Xyz"};` – MSalters Nov 21 '13 at 12:51

score 1 · Answer 2 · answered Nov 21 '13 at 10:33

You're assigning an Aircrafts object into a pointer to Aircrafts. This doesn't work.

Looking at your code, you don't need any dynamic allocation (= new) at all. Just do this:

void main()
{

   vector <Aircrafts> aircraft_list;

   aircraft_list.push_back(Aircrafts("Abc", "Xyz"));
}

john · Answer 3 · 2013-11-21T10:46:13.537

1

No need for pointers

Aircrafts temp_aircraft("Abc", "Xyz");
aircraft_list.push_back(temp_aircraft);

Why do beginners love pointers?

EDIT I rest my case, the OP picked the answer that continued to use pointers, despite every other answer telling them that pointers were unnecessary.

edited Nov 21 '13 at 10:46

answered Nov 21 '13 at 10:33

john

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score 1 · Answer 4 · answered Nov 21 '13 at 10:33

First you declare temp_aircraft as a pointer to Aircrafts, which you then initialize using new correctly. However, you then try to assign a non-pointer object to the pointer.

There is no need for pointers here, just create the object and push it into the container in one go:

aircraft_list.push_back(Aircrafts("Abc", "Xyz"));

This will work with your class even if you haven't defined an explicit copy-assignment operator (the compiler will create a simple for you). But you might want to learn about the rule of three anyway.

score 1 · Answer 5 · answered Nov 21 '13 at 10:33

1

This line of code,

temp_aircraft = Aircrafts("Abc", "Xyz");

should be

temp_aircraft = new Aircrafts("Abc", "Xyz");

And remember to include semicolon at the end of the class.

class Aircrafts
{
   .....
}; // <-- semicolon here

answered Nov 21 '13 at 10:33

Deidrei

2,125
1
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1

Good spot on the semicolon, bad idea to introduce a memory leak. – MSalters Nov 21 '13 at 12:52

klm123 · Answer 6 · 2013-11-21T10:45:39.343

Instead of

temp_aircraft = new Aircrafts;
temp_aircraft = Aircrafts("Abc", "Xyz");

you should do:

temp_aircraft = new Aircrafts("Abc", "Xyz");

constructor Aircrafts() gives you Aircrafts object, meantime temp_aircraft is Aircrafts *

P.S. also you have memory leak problem. All what you have allocated with new you must free with delete when you don't need it anymore; You can do it like:

   Aircrafts *temp_aircraft;

   temp_aircraft = new Aircrafts;
   temp_aircraft = Aircrafts("Abc", "Xyz");
   aircraft_list.push_back(*temp_aircraft);
   delete temp_aircraft;

or may be you don't need a pointer at all. Same result you can achieve with one line:

   aircraft_list.push_back( Aircrafts("Abc", "Xyz") );

score 1 · Answer 7 · answered Nov 21 '13 at 10:38

1

no need for a temporary object.

int main()
{
   vector <Aircrafts> aircraft_list;
   aircraft_list.emplace_back("Abc", "Xyz");
}

answered Nov 21 '13 at 10:38

Walter

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score 0 · Answer 8 · answered Nov 21 '13 at 10:34

temp_aircraft is a pointer, so when you try to do

temp_aircraft = Aircrafts("Scenic", "Piper Arrow", 3, 120, 0, 0);

you are trying to use the assignment operator to assign a Aircrafts to temp_aircarft

You can just use this constructor when you say new:

   temp_aircraft = new Aircrafts("Abc", "Xyz");

(or whatever the line really is that gives the error)

Of course, when you then do

aircraft_list.push_back(*temp_aircraft);

you are going to forget to delete the pointer. As other answers say, you can (and should) do this without pointers.

score 0 · Answer 9 · answered Nov 21 '13 at 10:34

The problem is on this line: temp_aircraft = Aircrafts("Abc", "Xyz");

WHen you write Aircrafts("Abc", "Xyz"), you create an object of the class Aircrafts, and you try to affect it to a variable of type Aircrafts* (pointer to Aircrafts). If you want to create a pointer, use the operator new, like this :

temp_aircraft = new Aircrafts("Abc", "Xyz");

If you don't want a pointer, create your variable with the Aircraft type, like this:

Aircrafts temp_aircraft;

Here, you mix the two ways, that's why it doesn't work.

C++ cannot convert 'type' to 'type*'

9 Answers9