Static Class vs Singleton [duplicate]

Question

So, pretty simple question. Ignoring the implications of over-use of the singleton pattern. I'm trying to find a reliable singleton patter in Objective-C. I have come across this:

@implementation SomeSingleTonClass  static SomeSingleTonClass* singleInstance;  + (SomeSingleTonClass*)getInstance {     static dispatch_once_t dispatchOnceToken;      dispatch_once(&dispatchOnceToken, ^{         singleInstance = [[SomeSingleTonClass alloc] init];     });      return singleInstance; }  - (void)someMethodOnTheInstance {     NSLog(@"DO SOMET WORK") }  @end 

This I am fairly happy with but it leads to a lot of this:

[[SomeSingleTonClass getInstance] someMethodOnTheInstance]; 

My question is, why is this better than a purely static class.

@implementation SomeStaticClass  static NSString* someStaticStateVariable;  - (id)init {     //Don't allow init to initialize any memory state     //Perhaps throw an exception to let some other programmer know     //not to do this     return nil; }  + (void)someStaticMethod {     NSLog(@"Do Some Work"); } 

All you really gain, is mildly cleaner looking method calls. Basically you swap out this:

[[SomeSingleTonClass getInstance] someMethodOnTheInstance]; 

For this

[SomeStaticClass someStaticMethod]; 

This is a minor simplification for sure, and you can always store the instance within your class. This is more intellectual curiosity, what Objective-C god am I pissing off by using static classes instead of singletons? I'm sure I can't be the first person to think this, but I promise, I did a duplicate search first. The few answers I found, I felt like were based on older versions of cocoa, because even the discussed singleton patterns seemed to suffer from threading issues.

Answer 1

Static class : Used when you want to group together utility methods that are state independent.

Singleton : Used when you have multiple methods that share a state.