Crash at dispatch_once(&onceToken, ^{

Question

+(Service *) sharedInstance
{
    static LocationService *instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{              <<<< Crash
        instance = [[self alloc]init];
    });
    return instance;
}

I am using the above shown code to create a singleton instance of service in my application. This is called from "AppDelegate application:willFinishLaunchingWithOptions:".

For most of the users, this code works fine. But for 2 users, the app crashes at "dispatch_once(&onceToken, ^{ " line.

They deleted the app and re-installed it. But they still see the issue. Only these 2 users are facing this issue. Others have never seen it. I have the .dsym, .crash and other relevant files to do further debugging. Just wanted to know how should I proceed with it? If someone has seen similar issue how did they proceed with fixing it?

http://stackoverflow.com/questions/13626513/dispatch-once-call-causes-crash — StefanS, Apr 06 '16 at 07:08
http://stackoverflow.com/questions/7570528/ios-singleton-class-crashes-my-app — StefanS, Apr 06 '16 at 07:08
Try removing the '= nil' definition from your static LocationService *instance declaration. I think variables declared as static are initialised as 0 by default. — DDP, Apr 06 '16 at 07:16
I am seeing this problem too, it's very strange - if anyone found a solution, please post :) — theLastNightTrain, Jun 20 '17 at 07:22
@theLastNightTrain, I was facing this issue because I was trying to call a method in CoreLocation framework that was not supported for the current version of OS. The error may not be exactly within this method — Parin Shah, Jun 22 '17 at 20:29

score -1 · Answer 1 · edited Apr 06 '16 at 09:41

-1

Don't use self. Because self is not available before the initilization of class. Instead you can use class name as follows.

+(Service *) sharedInstance
{
static LocationService *instance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{            
    instance = [[Service  alloc]init];
});
return instance;
}

edited Apr 06 '16 at 09:41

answered Apr 06 '16 at 08:08

Satyanarayana

1,059
6
16

4

This is wrong. In a class method, `self` refers to the class. – Phillip Martin Jul 19 '16 at 13:56
Thanks @andey for your answer – Parin Shah Jan 22 '17 at 05:08

Crash at dispatch_once(&onceToken, ^{

1 Answers1