Sample code for a Singleton that provides configuration or environment data

Environment.m

#import "Environment.h"

@implementation Environment

static Environment *sharedInstance = nil;

@synthesize myApiURL;

- (id)init
{
  self = [super init];

  if (self) {
    // Do Nada
  }

  return self;
}

- (void)initializeSharedInstance
{
  NSString* configuration = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"Configuration"];
  NSBundle* bundle = [NSBundle mainBundle];
  NSString* envsPListPath = [bundle pathForResource:@
"Environments" ofType:@"plist"];
  NSDictionary* environments = [[NSDictionary alloc] initWithContentsOfFile:envsPListPath];
  NSDictionary* environment = [environments objectForKey:configuration];

  self.myAPIURL = [environment valueForKey:@"myAPIURL"];
  [environments release];
}

#pragma mark - Lifecycle Methods

+ (Environment *)sharedInstance
{
  @synchronized(self) {
    if (sharedInstance == nil) {
      sharedInstance = [[self alloc] init];
      [sharedInstance initializeSharedInstance];
    }
    return sharedInstance;
  }
}

- (NSUInteger) retainCount
{
  return NSUIntegerMax;
}

- (void) release
{
  // Do Nada
}

- (id) autorelease
{
  return self;
}

- (id) retain
{
  return self;
}

- (void) dealloc
{
  [super dealloc];
}

@end