NSOperationQueue ....unrecognized selector sent - ios

Question

I am trying to implement a contact app.
In the MyContactsViewController, I am trying to get access to Contacts and if the access is granted I will fetch the contacts from my address book. The ContactHandler is my model class(singleton) which has the method called getAllContacts to get the contacts in a NSMutableArray.
- (void)viewDidLoad {
[super viewDidLoad];
contactHandler = [ContactHandler sharedInstance];
if(!self.accessGranted){
NSOperationQueue *queue =[[ NSOperationQueue alloc]init];
[queue performSelectorOnMainThread:#selector(getAccessToAddressBook) withObject:self waitUntilDone:YES];
contactList = [contactHandler getAllContacts];
}
else{
contactList = [contactHandler getAllContacts];
}
}
-(BOOL)getAccessToAddressBook{
CNContactStore * contactStore = [[CNContactStore alloc] init];
if( [CNContactStore authorizationStatusForEntityType:CNEntityTypeContacts] == CNAuthorizationStatusNotDetermined){
[contactStore requestAccessForEntityType:CNEntityTypeContacts completionHandler:^(BOOL granted, NSError * _Nullable error) {
if(granted){
self.accessGranted = YES;
}
else{
self.accessGranted = NO;
}
}];
}
else if( [CNContactStore authorizationStatusForEntityType:CNEntityTypeContacts]== CNAuthorizationStatusAuthorized){
self.accessGranted = YES;
}
else{
self.accessGranted = NO;
}
return self.accessGranted;
}
But I am getting this error -
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSOperationQueue getAccessToAddressBook]: unrecognized selector sent to instance 0x137630700'
Can anyone please help.

Answer 1

Your problem is this line:
[queue performSelectorOnMainThread:#selector(getAccessToAddressBook) withObject:self waitUntilDone:YES];
You're asking queue to perform getAccessToAddressBook when is self who has this selector
If you want to run the method getAccessToAddressBook on the queue, you can use - addOperationWithBlock:

Answer 2

As in this line: performSelectorOnMainThread you are passing withObject:self, where as in method definition i.e (BOOL)getAccessToAddressBookyou are not using it, which is causing the crash, so make withObject:nil , if you don't want to pass any object or value to the method.
Change this line:-
[queue performSelectorOnMainThread:#selector(getAccessToAddressBook) withObject:self waitUntilDone:YES];
to this:-
[queue performSelectorOnMainThread:#selector(getAccessToAddressBook) withObject:nil waitUntilDone:YES];
Or the better approach will be to write like this:-
NSOperationQueue *opQueue=[NSOperationQueue new];
NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(getAccessToAddressBook) object:nil];
[opQueue addOperation:op ];