What is SharedInstance actually?

Question

What is sharedInstance actually? I mean what is the usage?

Currently I\'m having some problem in communicating between 2 different files.

Here\'s my question:<

Answer 1

Shared Instance is a process by which you can access the same instance or object of a class anywhere in the project. The main idea behind this is to return the same object each time a method is called so that the values/properties stored in the instance can be used anywhere in the application.

This can be done in 2 simple process as follows:-

1) Using a static variable initialised only once

@implementation SharedInstanceClass

static SharedInstanceClass *sharedInstance = nil;

+ (id)sharedInstanceMethod
{
    @synchronized(self) {
        if (sharedInstance == nil) {
            sharedInstance = [SharedInstanceClass new];
        }
    }
    return sharedInstance;
}

@end

2) Using GCD's :-

+ (id)sharedInstance{
    static dispatch_once_t onceToken;
    static SharedInstanceClass *sharedInstance = nil;
    dispatch_once(&onceToken, ^{
        sharedInstance = [SharedInstanceClass new];
    });
    return sharedInstance;
}

These have to be called as:-

SharedInstanceClass *instance = [SharedInstanceClass sharedInstance];

Thus everytime the same instance will be returned from the function and the values set to the properties will be retained and can be used anywhere in the application.

Regards,