How to include C file in iOS project

Question

I had this code in one my view controller:

int randomNumber =  (arc4random() % 1) + 6;

Because I will need it on more places, I decided to made it as function. But I did it as C function, old habits die hard.

Now I have file WOC_Random.c with this content

#include <stdio.h>
#include <stdlib.h> // for arc4random() function

#ifndef WOC_Random_C
#define WOC_Random_C


int randomInt(int startInt, int endInt)
{
    int randomNumber =  (arc4random() % startInt) + endInt;

    return randomNumber;
}

#endif

Now code in my view controller is:

int randomNumber =  randomInt(1, 6);

But I have problem in linking, this is error:

duplicate symbol _randomInt in:
/Users/Mac/Library/Developer/Xcode/DerivedData/GuessTheNumber-gjovdrsarctubnbqhczqukvahwgb/Build/Intermediates/GuessTheNumber.build/Debug-iphonesimulator/GuessTheNumber.build/Objects-normal/i386/GTN_FirstViewController.o
/Users/Mac/Library/Developer/Xcode/DerivedData/GuessTheNumber-gjovdrsarctubnbqhczqukvahwgb/Build/Intermediates/GuessTheNumber.build/Debug-iphonesimulator/GuessTheNumber.build/Objects-normal/i386/WOC_Random.o
ld: 1 duplicate symbol for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I do have vague understanding, of problem.
But do not know how to fixit ?
So how to fix it, do I need some argument to linker or compiler ?

Also, in case like this when I just have some simple function to implement what is the best way to do it for iOS development, as C function or is it better to do it as class function in Object C ?

Answer 1

You need to add Header file (like WOC_Random.h) in which you will declare the function

int randomInt(int startInt, int endInt);

Then define that function in WOC_Random.c. And then include WOC_Random.h in the class you want to use the function.