incompatible types in assignment of 'int*' to 'int [0]'

Question

I was coding a class for "a kind of gun". I have this code for the classes:
Gun.h:

#ifndef Gun_h
#define Gun_h
#include "Arduino.h"
class Gun
{
 public:
 Gun(String identifier, String name, int teamIRCodes[]);
 String getIdentifier();
 String getName();
 int getIRCode();
 private:
 String _identifier;
 String _name;
 int _teamIRCodes[];
};
#endif

Gun.cpp:

#include "Arduino.h"
#include "Gun.h"
Gun::Gun(String identifier, String name, int teamIRCodes[])
{
 _identifier = identifier;
 _name = name;
 _teamIRCodes = teamIRCodes;
}
String Gun::getIdentifier(){
 return _identifier;
}
String Gun::getName(){
 return _name;
}
int Gun::getIRCode(){
 return _teamIRCodes[1];
}

It returns me this error while compiling:

sketch\Gun.cpp: In constructor 'Gun::Gun(String, String, int*)':
Gun.cpp:8: error: incompatible types in assignment of 'int*' to 'int [0]'
 _teamIRCodes = teamIRCodes;
 ^
exit status 1
incompatible types in assignment of 'int*' to 'int [0]'

Answer 1

The issue is with flexible array int _teamIRCodes[]; This is an old technique which I don't recommend. But if you want to use it, you need you use malloc to create a class object, adding on enough space for the array:

// Allocate space for the class AND the array
Gun *gun = (Gun *)malloc(sizeof(Gun) + sizeof(teamIRCodes));

However, this does not call the ctor, and you still have to manually copy the data:

for(int i = 0; i < (sizeof(teamIRCodes) / sizeof(teamIRCodes[0])); i++) {
 gun->_teamIRCodes[i] = teamIRCodes[i];
}

I think it's much simpler to use a pointer:

int* _teamIRCodes;

Then you can make your ctor:

Gun(String identifier, String name, int teamIRCodes[], int numberOfCodes) {
 _teamIRCodes = new int[numberOfCodes];
 // memcpy does the same thing as the for loop - copies the array
 memcpy(_teamIRCodes, teamIRCodes, sizeof(teamIRCodes[0]) * numberOfCodes);
}

And don' forget to add a dtor:

~Gun() {
 delete [] _teamIRCodes;
}

Or, if teamIRCodes is persistent throughout the lifetime of the object, you can just use a pointer to it:

 class Gun {
 public:
 int *_teamIRCodes;
 int _numberOfCodes;
 Gun(String identifier, String name, int teamIRCodes[], int numberOfCodes) {
 _teamIRCodes = teamIRCodes;
 _numberOfCodes = numberOfCodes;
 };

(Maybe this is an Arduino thing as this is the 2nd flexible array question I've seen today).

Answer 2

Ok, using this worked:
Replace

_teamIRCodes = teamIRCodes;

For

for(int i = 0; i < (sizeof(teamIRCodes)/sizeof(int)) ;i++)
 _teamIRCodes[i] = teamIRCodes[i];

Needed to iterate through array, cannot copy full array.

• 001: Close, but where do you allocate space for _teamIRCodes?
• Arnyminer Z: Doesn't it initialize with a value of 0? In Gun::Gun(String identifier, String name, int teamIRCodes[]) I add all the values
• Arnyminer Z: By now, it worked
• Arnyminer Z: Ok, it complied, but it seems that not working