How to create an array which can store two types of data

[cj179]

Hello, fellows:

I having difficulties on creating an array which can store two different data types, for example: string and int, in C++. Some of the websites told me it is impossible. Or use class to do it. Could anyone give me a hand on this. Thank you every much!

[Banfa]

A class or structure is the way to go, you could start by reading this.

[weaknessforcats]

Do you know about class templates yet?

template<class T>
class Data
{
T theValue
//class methods omitted for brevity
};

Data<int> arr[100]; //array of 100 Data objects containing ints
Data<string> arr1[100]; //array of 100 Data objects containing strings

[rakchha]

Hello, fellows:

I having difficulties on creating an array which can store two different data types, for example: string and int, in C++. Some of the websites told me it is impossible. Or use class to do it. Could anyone give me a hand on this. Thank you every much!

An indirect way to do this is to create an array of struct which itself is union of two or more data types eg

union u
{
int i;
char j; //for storing string u can keep char *
} ;

struct s
{
int eletype; //say int =0, char =1 and so on
union u data;
};

struct s array[10];
array[0].eletype = 0; //store int
array[0].data = 12;

array[1].eletype = 1;
array[1].data = 'g';

[cj179]

Thanks for the reply and I have found them being very helpful to me.

But I have a question on the Class template approach, is it still using two arrays rather than one. because I have to define two arrays when I instantiate an object of this class. Have I misunderstand this method?

Thanks to everyone again.

[cj179]

When I implementing the struct mehod in DEV c++ , I got this error as below:

24 E:\new c++\c++290307\ltest1.cpp no match for 'operator=' in 'array[0].main()::s::data = 12'

Does it mean I have to define a operator in the class, how to do it?

thanks

[Banfa]

When I implementing the struct mehod in DEV c++ , I got this error as below:

24 E:\new c++\c++290307\ltest1.cpp no match for 'operator=' in 'array[0].main()::s::data = 12'

Does it mean I have to define a operator in the class, how to do it?

thanks

May be seeing the code line would help.

[cj179]

Hi, here is the code with error I mentioned early on:

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


using namespace std;

int main(){
union u
{
int i;
char j; //for storing string u can keep char *
} ;

struct s
{
int eletype; //say int =0, char =1 and so on
union u data;
};

struct s array[10];
array[0].eletype = 0; //store int
array[0].data = 12;

array[1].eletype = 1;
array[1].data = 'g';


system("PAUSE");

}

[Banfa]

array[0].data = 12;

array[0].data is of type union u and does not support the = operator (unless you write a function for it, you probably want 1 of these 2 lines

array[0].data.i = 12;
array[0].data.j = 12;
 

[cj179]

Thank you for the reply. If it is possible, could you give me some hints for how to write this function for =operator?
Thank you

[Banfa]

Read This.