EXC_BAD_ACCESS on a dispatch_get_main_queue()
<p>I have this code, and some times the variable dConfiguration is Nil and I get a EXC_BAD_ACCESS error and most of the time the variable said 0 key/value pairs, and the error is almost imposible to reproduce, I just click my button and most of the time work but in rare occasions it fails.</p>

<pre><code>serviceData = data;
dispatch_async(dispatch_get_main_queue(), ^{
    [loading removeFromSuperview];
    _tvTable.hidden = NO;
    dConfiguration =[NSJSONSerialization JSONObjectWithData:serviceData options:kNilOptions error:nil];
    if (![[dConfiguration objectForKey:@"NumberOfLines"] isEqual: [NSNull null]]) {
        _NumberOfLines = [[dConfiguration objectForKey:@"NumberOfLines"] integerValue];
    } else {
        _NumberOfLines = 1;
    }
    if(badget!=nil){
        dBadgets = [NSJSONSerialization JSONObjectWithData:badget options:kNilOptions error:nil];
    }
    dValue = [dConfiguration objectForKey:sButtonType];
    RowCount = (int)dValue.count;
    [_tvTable numberOfRowsInSection:RowCount];
    [self loadTable];
});
</code></pre>

<p>This variable is declared as global in the implementation:</p>

<pre><code>@implementation vcTableViewEventsManagerEvents {
    NSDictionary *dConfiguration;
}
</code></pre>

<p>I have never implemented the alloc init code:</p>

<pre><code>dConfiguration = [[NSDictionary alloc] init];
</code></pre>

<p>Does this can be the problem? if I always init the variable this error will not occur? It is a good practice to always do the initialisation? Where can I see a more detailed information of the EXC_BAD_ACCESS?</p>

<p>Thanks to all your help. </p>

<p><strong>UPDATE 1</strong></p>

<p>I have tried the to see the error as all commented and maybe I'm doing something wrong because the error variable is nil this are the screen shoots:</p>

<p><a href="https://i.stack.imgur.com/Y5ceu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Y5ceu.png" alt="enter image description here"></a>  </p>

<p><a href="https://i.stack.imgur.com/e91sW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/e91sW.png" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/KCtfX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KCtfX.png" alt="enter image description here"></a></p>

<p>In this particular time the variable dConfiguration said 0 key/value pairs because I added the alloc init.</p>

<p>I have tried with double click and changing from the tabbar items as fast as I can and sometimes work and some times it does not.</p>

<p><strong>UPDATE 2</strong></p>

<p>As you asked this is the BT of the error:</p>

<blockquote>
  <p>thread #1: tid = 0x7bfdfd, 0x2537dd52 Foundation<code>newJSONString + 98,
  queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1,
  address=0x3fe64a2)
      frame #0: 0x2537dd52 Foundation</code>newJSONString + 98
      frame #1: 0x2537d300 Foundation<code>newJSONValue + 1976
      frame #2: 0x2537cf04 Foundation</code>newJSONValue + 956
      frame #3: 0x2537d380 Foundation<code>newJSONValue + 2104
      frame #4: 0x2537ca80 Foundation</code>-[_NSJSONReader parseUTF8JSONData:skipBytes:options:] + 176
      frame #5: 0x2537c88e Foundation<code>-[_NSJSONReader parseData:options:] + 238
      frame #6: 0x2537c718 Foundation</code>+[NSJSONSerialization JSONObjectWithData:options:error:] + 156
      frame #7: 0x00121b24 guestperience<code>__43-[vcTableViewEventsManagerEvents
  checkJson]_block_invoke_2(.block_descriptor=0x17040f40) + 244 at
  vcTableViewEventsManagerEvents.m:298
      frame #8: 0x00495b7e libdispatch.dylib</code>_dispatch_call_block_and_release + 10
      frame #9: 0x00495b6a libdispatch.dylib<code>_dispatch_client_callout + 22
      frame #10: 0x0049a654 libdispatch.dylib</code>_dispatch_main_queue_callback_4CF + 1680
      frame #11: 0x24b81bdc CoreFoundation<code>__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 8
      frame #12: 0x24b800d6 CoreFoundation</code>__CFRunLoopRun + 1574
      frame #13: 0x24acf2e8 CoreFoundation<code>CFRunLoopRunSpecific + 520
      frame #14: 0x24acf0d4 CoreFoundation</code>CFRunLoopRunInMode + 108
      frame #15: 0x260bfac8 GraphicsServices<code>GSEventRunModal + 160
      frame #16: 0x291940b8 UIKit</code>UIApplicationMain + 144
      frame #17: 0x001cb6f0 guestperience<code>main(argc=1, argv=0x00473b5c) + 106 at main.m:16
      frame #18: 0x24777872 libdyld.dylib</code>start + 2</p>
</blockquote>

<p><strong>UPDATE 3</strong></p>

<p>I have executed this command in the console to see the JSON and to me looks correct:</p>

<pre><code>(lldb) po (NSString *)[[NSString alloc] initWithData:serviceData encoding:4]

{
    "BackgroundImage": null,
    "ButtonGallery": null,
    "Buttons": null,
    "ButtonsEvents": [{
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "04 JUN 2016 - Horario: 11.00 - 18.00",
        "Id": 23,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_15f37703-f0a0-4f10-be70-76e0118fa9f9_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_15f37703-f0a0-4f10-be70-76e0118fa9f9_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "134",
        "ItemType": null,
        "JsonConfigFile": "134es",
        "Label": "Brazil Pool Party",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Brazil Pool Party",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "23 JUN 2016 - Horario: 20:00 - 01:00",
        "Id": 29,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_5af125bb-1bdf-4fcf-9306-3b565cdbb928_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_5af125bb-1bdf-4fcf-9306-3b565cdbb928_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "140",
        "ItemType": null,
        "JsonConfigFile": "140es",
        "Label": "Noche de San Juan",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche de San Juan",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "02 JUL 2016 - Horario: 21:00 - 1:00",
        "Id": 30,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_7227de52-8d27-4a65-bdf7-dea08e37b968_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_7227de52-8d27-4a65-bdf7-dea08e37b968_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "141",
        "ItemType": null,
        "JsonConfigFile": "141es",
        "Label": "Noche Amàre",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche Amàre",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "09 JUL 2016 - Horario: 22:00 - 00:00",
        "Id": 28,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_4ad05ca3-c345-4a6f-aeb9-972610056b86_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_4ad05ca3-c345-4a6f-aeb9-972610056b86_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "139",
        "ItemType": null,
        "JsonConfigFile": "139es",
        "Label": "Noche Flamenca Beach",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche Flamenca Beach",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "20 JUL 2016 - Horario: 19:00 - 22:00",
        "Id": 27,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_161bab39-5ac6-43a0-84c4-5c0fa764b5b0_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_161bab39-5ac6-43a0-84c4-5c0fa764b5b0_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "138",
        "ItemType": null,
        "JsonConfigFile": "138es",
        "Label": "Noche de luna llena",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche de luna llena",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "23 JUL 2016 - Horario: 21:00 - 00:00",
        "Id": 26,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_c657d56d-5f24-4f28-8d0c-66afb2fae1ad_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_c657d56d-5f24-4f28-8d0c-66afb2fae1ad_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "137",
        "ItemType": null,
        "JsonConfigFile": "137es",
        "Label": "Noche cubana",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche cubana",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "06 AGO 2016 - Horario: 22:00 - 00:00",
        "Id": 31,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_98032ab6-b689-42d6-b19b-6b82705478a3_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_98032ab6-b689-42d6-b19b-6b82705478a3_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "142",
        "ItemType": null,
        "JsonConfigFile": "142es",
        "Label": "Noche Flamenca Beach",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche Flamenca Beach",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "13 AGO 2016 - Horario: 21:00 - 00:00",
        "Id": 32,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_447f28d9-ed38-4482-868e-74743cbb5a89_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_447f28d9-ed38-4482-868e-74743cbb5a89_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "143",
        "ItemType": null,
        "JsonConfigFile": "143es",
        "Label": "Noche cubana",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Noche cubana",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "10 SEP 2016 - Horario: 11:00 - 18:00",
        "Id": 33,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_a7328a94-d64d-4fd4-b0a1-a2c126c8c92c_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_a7328a94-d64d-4fd4-b0a1-a2c126c8c92c_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "144",
        "ItemType": null,
        "JsonConfigFile": "144es",
        "Label": "Pool Party",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Pool Party",
        "ViewController": 21
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "17 SEP 2016 - Horario: 12:00 - 18:00",
        "Id": 25,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_9f8af8e5-56d7-433f-9661-9403196faad8_x320.jpg",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_9f8af8e5-56d7-433f-9661-9403196faad8_x320.jpg",
        "ImageRetinaHeighlighted": null,
        "Item": "136",
        "ItemType": null,
        "JsonConfigFile": "136es",
        "Label": "Oktoberfest",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Oktoberfest",
        "ViewController": 21
    }],
    "ButtonsPromotions": [{
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 18,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_ba95942c-1ece-4332-9f95-eb3f95738f41_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_ba95942c-1ece-4332-9f95-eb3f95738f41_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "126",
        "ItemType": null,
        "JsonConfigFile": "126es",
        "Label": "Desayuna con Nosotros",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Desayuna con Nosotros",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 19,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_3b9f1e44-5f33-4eb9-987b-5e50dcaed2a7_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_3b9f1e44-5f33-4eb9-987b-5e50dcaed2a7_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "127",
        "ItemType": null,
        "JsonConfigFile": "127es",
        "Label": "Disfruta de Nuestra Cena Buffet",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Disfruta de Nuestra Cena Buffet",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 20,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_f0ec90c9-3383-48f7-b5cf-28a236aee9e9_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_f0ec90c9-3383-48f7-b5cf-28a236aee9e9_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "128",
        "ItemType": null,
        "JsonConfigFile": "128es",
        "Label": "Alquiler de Bicicletas Vintage",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Alquiler de Bicicletas Vintage",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 21,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_f72a03bf-ddd2-486e-a289-cb3e82bd08db_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_f72a03bf-ddd2-486e-a289-cb3e82bd08db_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "129",
        "ItemType": null,
        "JsonConfigFile": "129es",
        "Label": "Parking",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Parking",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 22,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_3dd87e35-2ae3-4ef2-a70a-f1b44e41d27a_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_3dd87e35-2ae3-4ef2-a70a-f1b44e41d27a_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "130",
        "ItemType": null,
        "JsonConfigFile": "130es",
        "Label": "Ofertas de Grab &amp; Go",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Ofertas de Grab &amp; Go",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 13,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_b8187a48-1b03-4b29-a403-f03af8433c4f_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_b8187a48-1b03-4b29-a403-f03af8433c4f_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "92",
        "ItemType": null,
        "JsonConfigFile": "92es",
        "Label": "Habitación \"The One\"",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Habitación \"The One\"",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 14,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_fc20ec9b-2107-4828-9796-d5234dbe80fd_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_fc20ec9b-2107-4828-9796-d5234dbe80fd_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "98",
        "ItemType": null,
        "JsonConfigFile": "98es",
        "Label": "Disfruta de una Salida de Habitación más Tarde",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Disfruta de una Salida de Habitación más Tarde",
        "ViewController": 20
    }, {
        "BadgeCount": 0,
        "ClientId": 0,
        "Frequency": "",
        "Id": 15,
        "Image": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_be514668-27d0-4ee8-995e-0f8f89936c9b_x320.png",
        "ImageHeighlighted": null,
        "ImageIconTitle": "",
        "ImageRetina": "http:\/\/ServerCloud.CloudApp.net\/DesktopServerCloud\/ClientData\/4\/Images\/GVT_be514668-27d0-4ee8-995e-0f8f89936c9b_x320.png",
        "ImageRetinaHeighlighted": null,
        "Item": "103",
        "ItemType": null,
        "JsonConfigFile": "103es",
        "Label": "Habitación categoría superior",
        "LongTitle": null,
        "Selector": "btnAction:",
        "SubLabel": null,
        "Title": "Habitación categoría superior",
        "ViewController": 20
    }],
    "ButtonsTabList": null,
    "DatePeriod": null,
    "Details": null,
    "Disclaimer": null,
    "MessageList": null,
    "NoBooking": null,
    "NumberOfLines": 2,
    "Pins": null,
    "Selector": null,
    "ServiceType": null,
    "TabList": null,
    "Texts": null,
    "Titles": null,
    "Url": null,
    "UserCode": null
}
</code></pre>