Am I on the right track with my singleton? - iphone

Question

I asked a question yesterday regarding my table view and linking unique detail views to each cell in the table view. I believe I got a good answer to my question here. (Hopefully you can read that post and see what I need). Basically I wanted to know if I am making my singleton correctly. Here is my code:
timerStore.h
#import "Tasks.h"
#interface timerStore : NSObject
{
NSMutableDictionary *allItems;
}
+(timerStore *)sharedStore;
-(NSDictionary *)allItems;
-(NSTimer *)createTimerFor:(Tasks *)t inLocation: (NSIndexPath *)indexPath;
-(void)timerAction;
#end
timerStore.m
#implementation timerStore
+(timerStore *)sharedStore{
static timerStore *sharedStore = nil;
if (!sharedStore)
sharedStore = [[super allocWithZone:nil]init];
return sharedStore;
}
+(id)allocWithZone:(NSZone *)zone{
return [self sharedStore];
}
-(id)init {
self = [super init];
if (self) {
allItems = [[NSMutableDictionary alloc]init];
}
return self;
}
-(NSDictionary *)allItems{
return allItems;
}
-(NSTimer *)createTimerFor:(Tasks *)t inLocation: (NSIndexPath *)indexPath {
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:t.timeInterval target:self selector:#selector(timerAction) userInfo:nil repeats:1.0];
[allItems setObject:timer forKey:indexPath];
return timer;
}
-(void)timerAction{
//custom properties here
}
#end
I'm kind of confused because I was under the impression that a cell's index path gets recycled as you scroll down (dequeue). I may be wrong though. Anyway, am I on the right path to making a singleton as the guy in the link suggested?

Answer 1

The best way to implement App Singleton is as follows
Header file
#import <Foundation/Foundation.h>
#interface AppSingleton : NSObject
#property (nonatomic, retain) NSString *username;
+ (AppSingleton *)sharedInstance;
#end
Implementation File
#import "AppSingleton.h"
#implementation AppSingleton
#synthesize username;
+ (AppSingleton *)sharedInstance {
static AppSingleton *sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
// Initializing
- (id)init {
if (self = [super init]) {
username = [[NSString alloc] init];
}
return self;
}
#end
Note:
What this does is it defines a static variable (but only global to this translation unit) called sharedInstance which is then initialised once and only once in sharedInstance Method. The way we ensure that it’s only created once is by using the dispatch_once method from Grand Central Dispatch (GCD). This is thread safe and handled entirely by the OS for you so that you don’t have to worry about it at all.
Using Singleton To set value
[[AppSingleton sharedInstance] setUsername:#"codebuster"];
Using Singleton to get value.
NSString *username = [[AppSingleton sharedInstance] username];
Further Reference and Reading