Objective C - Static and global variable?

Question

In my .m file for a class named Ad , I have 3 static strings

static NSString *AdStateDisabled = @"disable";
static NSString *AdStateExpired = @"expired";
static NSString *AdStateActive = @"active";

I can simply use these static variables in the current class, but i cannot call them from any other class, is there a way to make these static variables global? So for example in my viewcontroller class i can do something like.

//HomeViewController.m
if ([self.ad.state isEqual:Ad.AdStateDisabled])
{
     //do something
}

Solution 1

You could add the following declarations to your HomeViewController.h header, which would then need to be imported anywhere you wanted access to the strings.

//HomeViewController.h
extern NSString *AdStateDisabled;
extern NSString *AdStateExpired;
extern NSString *AdStateActive;

Then alter your definitions to remove 'static'.

//HomeViewController.m
NSString *AdStateDisabled = @"disable";
NSString *AdStateExpired = @"expired";
NSString *AdStateActive = @"active";

If you don't want a user of the strings to have to import HomeViewController.h then you could also just define those strings in AdState.h and put the definitions into AdState.m (and remove them from HomeViewController.m) after which users of the string would just need to import AdState.h to use the strings.

Solution 2

First, remove the static. Static variables and functions in C and Objective-C mean that they're visible only to the current compilation unit (that is more or less: only the file that you've declared the statix variable in can see it).

Next, you also need to declare the variables in a public header file with "extern", like the one of the class associated with the class:

extern NSString *AdStateDisabled;

You can then use them in other files as well, but you would not access them as "Ad.AdStateDisabled" but just as "AdStateDisabled".

Comments

[Dario]

Hey I made a gist some time ago, not ARC compatible but it can actually be used in ARC by using the assign methods and specifying strong or weak references. It's a bit closer to what the original question asked: gist.github.com/darionco/03649feeee57f86fee3f