Question

The following array x is not large, but it is my example array.

float x[4] = {1.0f, 2.0f, 4.0f, 8.0f};

Say, I want to use the array in my ViewController BSViewController.h/.m . I have included BSParam.h in BSViewController.h, but I don’t know what else to do to use x in BSViewController.m

Below is the code so far for my class which will containt my constant arrays.

//
//  BSParam.h

#import <Foundation/Foundation.h>

@interface BSParam : NSObject

@end



//
//  BSParam.m

#import "BSParam.h"

@implementation BSParam

#include <stdio.h>


float x[4] = {1.0f, 2.0f, 4.0f, 8.0f};

@end

Answer 1

1) If you want to make it available outside of your class, use the extern keyword to make it available:

//  BSParam.h
extern float x[4];


//  BSParam.m
#import "BSParam.h"    
float x[4] = { 1.0f, 2.0f, 4.0f, 8.0f };

// BSViewController.m
#import "BSParam.h"

- (void)dummy {
  float t = x[0]; // etc.
}

2) Anyhow, this solution will make the variable x global, and available anywhere in your application, without any context/namespace to access it, so that’s not the optimal solution.

To make global values accessible to other parts of your application, you better use the Singleton pattern, or use a class method for that.

For example:

@interface BSParam : NSObject
+(float[4])x;
@end

@implementation BSParam
+(float[4])x {
    return (float[4]){ 1.0f, 2.0f, 4.0f, 8.0f };
}
@end

So that you can use [BSParam x] to access your array, instead of just x, adding some namespace to access this x array, avoiding the risk to mess with other local variables or whatever.