Where to store global constants in an iOS application?

Question

Most of the models in my iOS app query a web server. I would like to have a configuration file storing the base URL of the server. It will look something like this:

// production // static NSString* const baseUrl = "http://website.com/"  // testing static NSString* const baseUrl = "http://192.168.0.123/" 

By commenting out one line or the other, I can instantly change which server my models point to. My question is, what's the best practice for storing global constants in iOS? In Android programming, we have this built-in strings resource file. In any Activity (the equivalent of a UIViewController), we can retrieve those string constants with:

String string = this.getString(R.string.someConstant); 

I was wondering if the iOS SDK has an analogous place to store constants. If not, what is the best practice in Objective-C to do so?

Answer 1

Well, you want the declaration local to the interfaces it relates to -- the app-wide constants file is not a good thing.

As well, it's preferable to simply declare an extern NSString* const symbol, rather than use a #define:

---

SomeFile.h

extern NSString* const MONAppsBaseUrl; 

SomeFile.m

#import "SomeFile.h"  #ifdef DEBUG NSString* const MONAppsBaseUrl = @"http://192.168.0.123/"; #else NSString* const MONAppsBaseUrl = @"http://website.com/"; #endif 

---

Apart from the omission of the C++ compatible Extern declaration, this is what you will generally see used in Apple's Obj-C frameworks.

If the constant needs to be visible to just one file or function, then static NSString* const baseUrl in your *.m is good.