ignore negative indexes when using ListMonitor's safeIndex APIs

CoreStore/Observing/ListMonitor.swift

@@ -117,19 +117,11 @@ public final class ListMonitor<T: NSManagedObject> {
      */
     public subscript(safeSectionIndex sectionIndex: Int, safeItemIndex itemIndex: Int) -> T? {
         
-        CoreStore.assert(
+        guard let section = self.sectionInfoAtIndex(safeSectionIndex: sectionIndex) else {
-            !self.isPendingRefetch || NSThread.isMainThread(),
-            "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
-        )
             
-        guard let sections = self.fetchedResultsController.sections
+            return nil
-            where sectionIndex < sections.count else {
-                
-                return nil
         }
-        
+        guard itemIndex >= 0 && itemIndex < section.numberOfObjects else {
-        let section = sections[sectionIndex]
-        guard itemIndex < section.numberOfObjects else {
             
             return nil
         }
@@ -148,7 +140,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.objectAtIndexPath(indexPath) as! T
     }
     
@@ -201,7 +192,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return (self.fetchedResultsController.fetchedObjects as? [T]) ?? []
     }
     
@@ -214,12 +204,7 @@ public final class ListMonitor<T: NSManagedObject> {
     @warn_unused_result
     public func objectsInSection(section: Int) -> [T] {
         
-        CoreStore.assert(
+        return (self.sectionInfoAtIndex(section).objects as? [T]) ?? []
-            !self.isPendingRefetch || NSThread.isMainThread(),
-            "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
-        )
-        
-        return (self.fetchedResultsController.sections?[section].objects as? [T]) ?? []
     }
     
     /**
@@ -231,12 +216,7 @@ public final class ListMonitor<T: NSManagedObject> {
     @warn_unused_result
     public func objectsInSection(safeSectionIndex section: Int) -> [T]? {
         
-        CoreStore.assert(
+        return (self.sectionInfoAtIndex(safeSectionIndex: section)?.objects as? [T]) ?? []
-            !self.isPendingRefetch || NSThread.isMainThread(),
-            "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
-        )
-        
-        return (self.fetchedResultsController.sections?[section].objects as? [T]) ?? []
     }
     
     /**
@@ -251,7 +231,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.sections?.count ?? 0
     }
     
@@ -267,7 +246,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.fetchedObjects?.count ?? 0
     }
     
@@ -308,7 +286,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.sections![section]
     }
     
@@ -325,13 +302,15 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
+        guard section >= 0 else {
             
+            return nil
+        }
         guard let sections = self.fetchedResultsController.sections
             where section < sections.count else {
                 
                 return nil
         }
-        
         return sections[section]
     }
     
@@ -347,7 +326,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.sections ?? []
     }
     
@@ -365,7 +343,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.sectionForSectionIndexTitle(title, atIndex: index)
     }
     
@@ -381,7 +358,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.sectionIndexTitles
     }
     
@@ -398,7 +374,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return (self.fetchedResultsController.fetchedObjects as? [T] ?? []).indexOf(object)
     }
     
@@ -415,7 +390,6 @@ public final class ListMonitor<T: NSManagedObject> {
             !self.isPendingRefetch || NSThread.isMainThread(),
             "Attempted to access a \(typeName(self)) outside the main thread while a refetch is in progress."
         )
-        
         return self.fetchedResultsController.indexPathForObject(object)
     }
     
@@ -439,7 +413,6 @@ public final class ListMonitor<T: NSManagedObject> {
             NSThread.isMainThread(),
             "Attempted to add an observer of type \(typeName(observer)) outside the main thread."
         )
-        
         self.removeObserver(observer)
         
         self.registerChangeNotification(
@@ -513,7 +486,6 @@ public final class ListMonitor<T: NSManagedObject> {
             NSThread.isMainThread(),
             "Attempted to add an observer of type \(typeName(observer)) outside the main thread."
         )
-        
         self.removeObserver(observer)
         
         self.registerChangeNotification(
@@ -657,7 +629,6 @@ public final class ListMonitor<T: NSManagedObject> {
             NSThread.isMainThread(),
             "Attempted to add an observer of type \(typeName(observer)) outside the main thread."
         )
-        
         self.removeObserver(observer)
         
         self.registerChangeNotification(
@@ -832,7 +803,6 @@ public final class ListMonitor<T: NSManagedObject> {
             NSThread.isMainThread(),
             "Attempted to remove an observer of type \(typeName(observer)) outside the main thread."
         )
-        
         let nilValue: AnyObject? = nil
         setAssociatedRetainedObject(nilValue, forKey: &self.willChangeListKey, inObject: observer)
         setAssociatedRetainedObject(nilValue, forKey: &self.didChangeListKey, inObject: observer)