Question

There is a strange behavior in my code and I really don’t know how to solve it.
I have a Singleton class with this definition:

AppModelLocator.h>

#import <Foundation/Foundation.h>

@interface AppModelManager : NSObject

+ (AppModelManager *)sharedManager;

@end

AppModelLocator.m

#import "AppModelManager.h"

static AppModelManager *instance = nil;

@implementation AppModelManager

#pragma mark - Singletone
#pragma mark

+ (AppModelManager *)sharedManager
{
    @synchronized ([AppModelManager class]) {
        if (instance == nil) {
            instance = [AppModelManager new];
        }
    }

    return instance;
}

+ (id)alloc
{
    @synchronized ([AppModelManager class]) {
        NSAssert(instance == nil, @"Attempted to allocate the second instance of AppModelManager.");
        instance = [super alloc];
        return instance;
    }

    return nil;
}

@end

When I call [AppModelLocator sharedManager]somewhere in my code everything is fine. But when I call the singleton class after a specific line of code it throws me EXC_BAD_ACCESS (code=1, address=0xfffffeec) and refers to return instance in sharedManager definition in the singleton class.

That specific code is initializing a class that create a HTTP request and start sending the request but in the class is not any reference of AppModelLocator or something special. It is a simple creating of NSURLConnection and its delegate methods.

I used similar classes and approach in other applications and they are working fine and I wonder what is wrong with this class. I tried a dozen other ways of creating singleton class but none of them were useful.

Answer 1

Finally, I found what was wrong in the code. I made a NSURL instance dynamically and I used 3rd library to encrypt the URL. Something through the encoding caused the crash in special condition but I wonder why the exception raised after calling the singleton class. Anyway the issue was not because of the singleton definition as deanWombourne said.