components/Collections/examples/CollectionsEditingExample.m

/*
 Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

#import "supplemental/CollectionsEditingExample.h"

static const NSInteger kSectionCount = 10;
static const NSInteger kSectionItemCount = 5;
static NSString *const kReusableIdentifierItem = @"itemCellIdentifier";
static NSString *const HEADER_REUSE_IDENTIFIER = @"EditingExampleHeader";

@implementation CollectionsEditingExample {
  NSMutableArray <NSMutableArray *>*_content;
}

- (void)viewDidLoad {
  [super viewDidLoad];

  // Add button to toggle edit mode.
  [self updatedRightBarButtonItem:NO];

  // Register cell class.
  [self.collectionView registerClass:[MDCCollectionViewTextCell class]
          forCellWithReuseIdentifier:kReusableIdentifierItem];
  // Optional
  // Register section header class
  [self.collectionView registerClass:[MDCCollectionViewTextCell class]
          forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                 withReuseIdentifier:HEADER_REUSE_IDENTIFIER];

  // Populate content.
  _content = [NSMutableArray array];
  for (NSInteger i = 0; i < kSectionCount; i++) {
    NSMutableArray *items = [NSMutableArray array];
    for (NSInteger j = 0; j < kSectionItemCount; j++) {
      NSString *itemString = [NSString stringWithFormat:@"Section-%ld Item-%ld", (long)i, (long)j];
      [items addObject:itemString];
    }
    [_content addObject:items];
  }

  // Customize collection view settings.
  self.styler.cellStyle = MDCCollectionViewCellStyleCard;
}

- (void)updatedRightBarButtonItem:(BOOL)isEditing {
  self.navigationItem.rightBarButtonItem =
      [[UIBarButtonItem alloc] initWithTitle:isEditing ? @"Cancel" : @"Edit"
                                       style:UIBarButtonItemStyleDone
                                      target:self
                                      action:@selector(toggleEditMode:)];
}

- (void)toggleEditMode:(id)sender {
  BOOL isEditing = self.editor.isEditing;
  [self updatedRightBarButtonItem:!isEditing];
  [self.editor setEditing:!isEditing animated:YES];
}

#pragma mark - <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
  return [_content count];
}

- (NSInteger)collectionView:(UICollectionView *)collectionView
     numberOfItemsInSection:(NSInteger)section {
  return [_content[section] count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  MDCCollectionViewTextCell *cell =
      [collectionView dequeueReusableCellWithReuseIdentifier:kReusableIdentifierItem
                                                forIndexPath:indexPath];
  cell.textLabel.text = _content[indexPath.section][indexPath.item];
  return cell;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
           viewForSupplementaryElementOfKind:(NSString *)kind
                                 atIndexPath:(NSIndexPath *)indexPath {
  // If you have defined your own supplementary views, deque them here
  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
    MDCCollectionViewTextCell *sectionHeader =
        [collectionView dequeueReusableSupplementaryViewOfKind:kind
                                           withReuseIdentifier:HEADER_REUSE_IDENTIFIER
                                                  forIndexPath:indexPath];

    NSAssert(sectionHeader != nil, @"Unable to dequeue SupplementaryView");

    if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
      sectionHeader.textLabel.text =
          [NSString stringWithFormat:@"Section %lu Header", (long)indexPath.section];
    }

    return sectionHeader;
  }

  // Otherwise, pass the kind to super to let MDCCollectionViewController handle the request
  return [super collectionView:collectionView
      viewForSupplementaryElementOfKind:kind
                            atIndexPath:indexPath];
}

#pragma mark - <MDCCollectionViewEditingDelegate>

- (BOOL)collectionViewAllowsEditing:(UICollectionView *)collectionView {
  return YES;
}

- (BOOL)collectionViewAllowsReordering:(UICollectionView *)collectionView {
  return YES;
}

- (BOOL)collectionViewAllowsSwipeToDismissItem:(UICollectionView *)collectionView {
  return self.editor.isEditing;
}

- (void)collectionView:(UICollectionView *)collectionView
    willDeleteItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths {
  // First sort reverse order then remove. This is done because when we delete an index path the
  // higher rows shift down, altering the index paths of those that we would like to delete in the
  // next iteration of this loop.
  NSArray *sortedArray = [indexPaths sortedArrayUsingSelector:@selector(compare:)];
  for (NSIndexPath *indexPath in [sortedArray reverseObjectEnumerator]) {
    [_content[indexPath.section] removeObjectAtIndex:indexPath.item];
  }
}

- (void)collectionView:(UICollectionView *)collectionView
    willMoveItemAtIndexPath:(NSIndexPath *)indexPath
                toIndexPath:(NSIndexPath *)newIndexPath {
  if (indexPath.section == newIndexPath.section) {
    // Exchange data within same section.
    [_content[indexPath.section] exchangeObjectAtIndex:indexPath.item
                                     withObjectAtIndex:newIndexPath.item];
  } else {
    // Since moving to different section, first remove data from index path and insert
    // at new index path.
    id movedObject = [_content[indexPath.section] objectAtIndex:indexPath.item];
    [_content[indexPath.section] removeObjectAtIndex:indexPath.item];
    [_content[newIndexPath.section] insertObject:movedObject atIndex:newIndexPath.item];
  }
}

#pragma mark UICollectionViewFlowLayoutDelegate

- (CGSize)collectionView:(UICollectionView *)collectionView
                             layout:(UICollectionViewLayout *)collectionViewLayout
    referenceSizeForHeaderInSection:(NSInteger)section {
  return CGSizeMake(collectionView.bounds.size.width, MDCCellDefaultOneLineHeight);
}

#pragma mark - CatalogByConvention

+ (NSArray *)catalogBreadcrumbs {
  return @[ @"Collections", @"Cell Editing Example" ];
}

+ (BOOL)catalogIsPrimaryDemo {
  return NO;
}

+ (BOOL)catalogIsPresentable {
  return NO;
}

@end