Why my app doesn't compile when my NSFetchedResultsController properties is named "fetchedResultsController" and I override the setter selector?

Question

Hi everyone,
I'm struggling with a problem here. I cannot compile my app when I name a NSFetchedResultsController "fetchedResultController" and I override the setter selector.
How do you explain that? Is it a bug?
I'm using xCode Version 5.0.2 (5A3005) on OS X 10.9 (13A603).
Here is a sample of code showing the problem:
TestViewController.h
#import <UIKit/UIKit.h>
@interface TestViewController : UIViewController
@end
TestViewController.m
#import "TestViewController.h"
@interface TestViewController ()<NSFetchedResultsControllerDelegate>
@property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController;
@end
@implementation TestViewController
-(void)setFetchedResultsController:(NSFetchedResultsController *)fetchedResultsController
    if(_fetchedResultsController) _fetchedResultsController.delegate = nil;
    _fetchedResultsController = fetchedResultsController;
- (NSFetchedResultsController *)fetchedResultsController
    if (!_fetchedResultsController) // if no filter, no request
        static NSString *SomeCacheName = @"SomeCache";
        NSFetchRequest *request = [[NSFetchRequest alloc] init];
        [request setRelationshipKeyPathsForPrefetching:@[@"tags",@"tags.tagged_players"]];
        [NSFetchedResultsController deleteCacheWithName:SomeCacheName];
        _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:[NSManagedObjectContext defaultContext] sectionNameKeyPath:nil cacheName:SomeCacheName];
        NSError *error;
        ZAssert([_fetchedResultsController performFetch:&error], @"Event list fetch error. %@. %@", error, error.userInfo);
        _fetchedResultsController.delegate = self;
    return _fetchedResultsController;
@end

Answer 1

You have custom accessor methods so need to explicitly declare the instance variable _fetchedResultsController. Read this note under You Can Implement Custom Accessor Methods in Programming with Objective-C.
https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/Programmi ngWithObjectiveC/EncapsulatingData/EncapsulatingData.html
Note: The compiler will automatically synthesize an instance variable in all situations where it’s also synthesizing at least one accessor method. If you implement both a getter and a setter for a readwrite property, or a getter for a readonlyproperty, the compiler will assume that you are taking control over the property implementation and won’t synthesize an instance variable automatically.