NSFetchedResultsController extension for safely retrieving objects without raising 'NSInternalInconsistencyException'.

NSFetchedResultsController+SafeObjectAtIndexPath

//
//  NSFetchedResultsController+SafeObjectAtIndexPath.swift
//  This extension prevents the 'no object at index in section at index' exception.
//
//  Copyright (c) 2016 Thiago Pereira
//  MIT License, http://www.opensource.org/licenses/mit-license.php

import Foundation

extension NSFetchedResultsController{
   
   /// Check whether provided indexPath is valid.
   /// 
   /// - note: This method checks if self.section is greater than indexPath.section
   /// and if number of object in indexPath.section is greater than indexPath.row
   ///
   /// - parameter indexPath: indexPath to be checked.
   ///
   /// - returns: Whether indexPath has a value associated to it.
   private func hasObject(at indexPath : NSIndexPath) -> Bool{
      guard let sections = self.sections where sections.count > indexPath.section else {
         return false
      }
      
      let sectionInfo = sections[indexPath.section]
      
      guard sectionInfo.numberOfObjects > indexPath.row else {
         return false
      }
      
      return true
   }
   
   
   /// Check whether the object exists and returns it if true.
   ///
   /// - parameter indexPath: Indexpath of object.
   ///
   /// - returns: Object at indexPath if exists. Nil otherwise.
   func exceptionFreeObject(at indexPath : NSIndexPath) -> AnyObject?{
      guard self.hasObject(at: indexPath) else {
         return nil
      }
      
      return self.objectAtIndexPath(indexPath)
   }
}