What is the use of Singleton class in objective-c? [duplicate]

Answer 1

Here is an example and tutorial: http://www.galloway.me.uk/tutorials/singleton-classes/

Here is another one: How to create singleton class in objective C

Singleton contains global variables and global functions.It’s an extremely powerful way to share data between different parts of code without having to pass the data around manually.

Answer 2

A singleton is a special kind of class where only one instance of the class exists for the current process. In the case of an iPhone app, the one instance is shared across the entire app.

Have a look at these tutorials :

http://pixeleap.com/?p=19

http://www.codeproject.com/Tips/232321/Implement-Objective-C-Singleton-Pattern

http://xcodenoobies.blogspot.in/2012/08/how-to-pass-data-between.html

http://www.johnwordsworth.com/2010/04/iphone-code-snippet-the-singleton-pattern/

http://www.idev101.com/code/Objective-C/singletons.html

And this video tutorial :

http://www.youtube.com/watch?v=FTfEN8KQPK8

Answer 3

You normally use a Singleton when you want to expose something to the entire project, or you want a single point of entry to something. Imagine that you have a photos application, and 3 our 4 UIViewControllers need to access an Array with Photos. It might (most of the time it doesn't) make sense to have a Singleton to have a reference to those photos.

A quick implementation can be found here. And would look like this:

+ (id)sharedManager
{
  static id sharedManager;
  static dispatch_once_t once;
  dispatch_once(&once, ^{
    sharedManager = [[self alloc] init];
  });
  return sharedManager;
}

You can see other ways of implementing this pattern here.

In Swift 2.1 would look like this:

class Manager {

    static let sharedManager = Manager()
    private init() { }
}