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Updated Ash Furrow’s original.
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SixtyFrames authored and SixtyFrames committed Mar 30, 2015
1 parent 7fae742 commit 09a18ed
Showing 1 changed file with 108 additions and 119 deletions.
227 changes: 108 additions & 119 deletions AFMasterViewController.m
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Original file line number Diff line number Diff line change
Expand Up @@ -13,8 +13,8 @@

@implementation AFMasterViewController
{
NSMutableArray *_objectChanges;
NSMutableArray *_sectionChanges;
NSMutableDictionary *_objectChanges;
NSMutableDictionary *_sectionChanges;
}

- (void)awakeFromNib
Expand All @@ -27,8 +27,6 @@ - (void)viewDidLoad
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

_objectChanges = [NSMutableArray array];
_sectionChanges = [NSMutableArray array];
}

- (void)didReceiveMemoryWarning
Expand Down Expand Up @@ -102,155 +100,146 @@ - (NSFetchedResultsController *)fetchedResultsController
}

return _fetchedResultsController;
}
}

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
_objectChanges = [NSMutableDictionary dictionary];
_sectionChanges = [NSMutableDictionary dictionary];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{

NSMutableDictionary *change = [NSMutableDictionary new];

switch(type) {
case NSFetchedResultsChangeInsert:
change[@(type)] = @(sectionIndex);
break;
case NSFetchedResultsChangeDelete:
change[@(type)] = @(sectionIndex);
break;
if (type == NSFetchedResultsChangeInsert || type == NSFetchedResultsChangeDelete) {
NSMutableIndexSet *changeSet = _sectionChanges[@(type)];
if (changeSet != nil) {
[changeSet addIndex:sectionIndex];
} else {
_sectionChanges[@(type)] = [[NSMutableIndexSet alloc] initWithIndex:sectionIndex];
}
}

[_sectionChanges addObject:change];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
NSMutableArray *changeSet = _objectChanges[@(type)];
if (changeSet == nil) {
changeSet = [[NSMutableArray alloc] init];
_objectChanges[@(type)] = changeSet;
}

NSMutableDictionary *change = [NSMutableDictionary new];
switch(type)
{
switch(type) {
case NSFetchedResultsChangeInsert:
change[@(type)] = newIndexPath;
[changeSet addObject:newIndexPath];
break;
case NSFetchedResultsChangeDelete:
change[@(type)] = indexPath;
[changeSet addObject:indexPath];
break;
case NSFetchedResultsChangeUpdate:
change[@(type)] = indexPath;
[changeSet addObject:indexPath];
break;
case NSFetchedResultsChangeMove:
change[@(type)] = @[indexPath, newIndexPath];
[changeSet addObject:@[indexPath, newIndexPath]];
break;
}
[_objectChanges addObject:change];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
if ([_sectionChanges count] > 0)
{
[self.collectionView performBatchUpdates:^{
NSMutableArray *moves = _objectChanges[@(NSFetchedResultsChangeMove)];
if (moves.count) {
NSMutableArray *updatedMoves = [[NSMutableArray alloc] initWithCapacity:moves.count];

NSMutableIndexSet *insertSections = _sectionChanges[@(NSFetchedResultsChangeInsert)];
NSMutableIndexSet *deleteSections = _sectionChanges[@(NSFetchedResultsChangeDelete)];
for (NSArray *move in moves) {
NSIndexPath *fromIP = move[0];
NSIndexPath *toIP = move[1];

for (NSDictionary *change in _sectionChanges)
{
[change enumerateKeysAndObjectsUsingBlock:^(NSNumber *key, id obj, BOOL *stop) {

NSFetchedResultsChangeType type = [key unsignedIntegerValue];
switch (type)
{
case NSFetchedResultsChangeInsert:
[self.collectionView insertSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
break;
case NSFetchedResultsChangeDelete:
[self.collectionView deleteSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
break;
case NSFetchedResultsChangeUpdate:
[self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
break;
if ([deleteSections containsIndex:fromIP.section]) {
if (![insertSections containsIndex:toIP.section]) {
NSMutableArray *changeSet = _objectChanges[@(NSFetchedResultsChangeInsert)];
if (changeSet == nil) {
changeSet = [[NSMutableArray alloc] initWithObjects:toIP, nil];
_objectChanges[@(NSFetchedResultsChangeInsert)] = changeSet;
} else {
[changeSet addObject:toIP];
}
}];
}
} else if ([insertSections containsIndex:toIP.section]) {
NSMutableArray *changeSet = _objectChanges[@(NSFetchedResultsChangeDelete)];
if (changeSet == nil) {
changeSet = [[NSMutableArray alloc] initWithObjects:toIP, nil];
_objectChanges[@(NSFetchedResultsChangeDelete)] = changeSet;
} else {
[changeSet addObject:toIP];
}
} else {
[updatedMoves addObject:move];
}
} completion:nil];
}

if ([_objectChanges count] > 0 && [_sectionChanges count] == 0)
{
}

if ([self shouldReloadCollectionViewToPreventKnownIssue] || self.collectionView.window == nil) {
// This is to prevent a bug in UICollectionView from occurring.
// The bug presents itself when inserting the first object or deleting the last object in a collection view.
// http://stackoverflow.com/questions/12611292/uicollectionview-assertion-failure
// This code should be removed once the bug has been fixed, it is tracked in OpenRadar
// http://openradar.appspot.com/12954582
[self.collectionView reloadData];

if (updatedMoves.count) {
_objectChanges[@(NSFetchedResultsChangeMove)] = updatedMoves;
} else {

[self.collectionView performBatchUpdates:^{

for (NSDictionary *change in _objectChanges)
{
[change enumerateKeysAndObjectsUsingBlock:^(NSNumber *key, id obj, BOOL *stop) {

NSFetchedResultsChangeType type = [key unsignedIntegerValue];
switch (type)
{
case NSFetchedResultsChangeInsert:
[self.collectionView insertItemsAtIndexPaths:@[obj]];
break;
case NSFetchedResultsChangeDelete:
[self.collectionView deleteItemsAtIndexPaths:@[obj]];
break;
case NSFetchedResultsChangeUpdate:
[self.collectionView reloadItemsAtIndexPaths:@[obj]];
break;
case NSFetchedResultsChangeMove:
[self.collectionView moveItemAtIndexPath:obj[0] toIndexPath:obj[1]];
break;
}
}];
}
} completion:nil];
[_objectChanges removeObjectForKey:@(NSFetchedResultsChangeMove)];
}
}

[_sectionChanges removeAllObjects];
[_objectChanges removeAllObjects];
}

- (BOOL)shouldReloadCollectionViewToPreventKnownIssue {
__block BOOL shouldReload = NO;
for (NSDictionary *change in self.objectChanges) {
[change enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
NSFetchedResultsChangeType type = [key unsignedIntegerValue];
NSIndexPath *indexPath = obj;
switch (type) {
case NSFetchedResultsChangeInsert:
if ([self.collectionView numberOfItemsInSection:indexPath.section] == 0) {
shouldReload = YES;
} else {
shouldReload = NO;
}
break;
case NSFetchedResultsChangeDelete:
if ([self.collectionView numberOfItemsInSection:indexPath.section] == 1) {
shouldReload = YES;
} else {
shouldReload = NO;
}
break;
case NSFetchedResultsChangeUpdate:
shouldReload = NO;
break;
case NSFetchedResultsChangeMove:
shouldReload = NO;
break;
}
}];

NSMutableArray *deletes = _objectChanges[@(NSFetchedResultsChangeDelete)];
if (deletes.count) {
NSMutableIndexSet *deletedSections = _sectionChanges[@(NSFetchedResultsChangeDelete)];
[deletes filterUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(NSIndexPath *evaluatedObject, NSDictionary *bindings) {
return ![deletedSections containsIndex:evaluatedObject.section];
}]];
}

return shouldReload;
NSMutableArray *inserts = _objectChanges[@(NSFetchedResultsChangeInsert)];
if (inserts.count) {
NSMutableIndexSet *insertedSections = _sectionChanges[@(NSFetchedResultsChangeInsert)];
[inserts filterUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(NSIndexPath *evaluatedObject, NSDictionary *bindings) {
return ![insertedSections containsIndex:evaluatedObject.section];
}]];
}

UICollectionView *collectionView = self.collectionView;

[collectionView performBatchUpdates:^{
NSIndexSet *deletedSections = _sectionChanges[@(NSFetchedResultsChangeDelete)];
if (deletedSections.count) {
[collectionView deleteSections:deletedSections];
}

NSIndexSet *insertedSections = _sectionChanges[@(NSFetchedResultsChangeInsert)];
if (insertedSections.count) {
[collectionView insertSections:insertedSections];
}

NSArray *deletedItems = _objectChanges[@(NSFetchedResultsChangeDelete)];
if (deletedItems.count) {
[collectionView deleteItemsAtIndexPaths:deletedItems];
}

NSArray *insertedItems = _objectChanges[@(NSFetchedResultsChangeInsert)];
if (insertedItems.count) {
[collectionView insertItemsAtIndexPaths:insertedItems];
}

NSArray *reloadItems = _objectChanges[@(NSFetchedResultsChangeUpdate)];
if (reloadItems.count) {
[collectionView reloadItemsAtIndexPaths:reloadItems];
}

NSArray *moveItems = _objectChanges[@(NSFetchedResultsChangeMove)];
for (NSArray *paths in moveItems) {
[collectionView moveItemAtIndexPath:paths[0] toIndexPath:paths[1]];
}
} completion:nil];

_objectChanges = nil;
_sectionChanges = nil;
}

@end

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