LKAssetsLibrary provides grouping / filtering / sorting functions for ALAssetsLibrary.

Example: Grouped by month, Filtered with JPEG and PNG, Sorted in descenting

LKAssetsCollection
      |
      |--LKAassetsCollectionEntry (May 2014)
      |      |
      |      |--LKAsset (JPEG, 25 May 2014 10:00）
      |      |--LKAsset (JPEG, 13 May 2014 12:00）
      |      |--LKAsset (JPEG, 4 May 2014 23:00）
      |      :
      |
      |--LKAassetsCollectionEntry (Apr 2014)
      |      |
      |      |--LKAsset (JPEG, 25 Apr 2014 10:00）
      |      |--LKAsset (JPEG, 13 APr 2014 12:00）
      |      |--LKAsset (JPEG,  4 Apr 2014 23:00）
      |      :

Usage

Basic

LKAssetsLibrary has 3 basic classes:

LKAssetsLibrary
LKAassetsGroup
LKasset

These are wrapper classes for ALAssetsLibrary, ALAssetsGroup, ALAsset. They has convenience methods (e.g. LKAsset.thumbnail, LKAsset.date, ...).

LKAssetsLibrary posts a notification after fetchs assets. You can handle the assets by observing the notification.

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(_assetsLibraryDidSetup:)
                                             name:LKAssetsLibraryDidSetupNotification
                                           object:nil];
    self.assetsLibrary = [LKAssetsLibrary assetsLibrary];
    [self.assetsLibrary reload];
}

Once you recieve the notification, you use LKAssetGroup or LKAsset.

- (void)_assetsLibraryDidSetup:(NSNotification*)notification
{
    [self.tableView reloadData];
}

Using LKAssetsGroup for UITableViewCell.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"GroupCell" forIndexPath:indexPath];

    LKAssetsGroup* assetsGroup = self.assetsLibrary.assetsGroups[indexPath.row];   
    cell.imageView.image = assetsGroup.posterImage;
    cell.textLabel.text = assetsGroup.description;
    return cell;
}

Using for UICollectionViewCell.

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    AssetCell* cell = (AssetCell*)[collectionView dequeueReusableCellWithReuseIdentifier:@"AssetCell"
                                                                           forIndexPath:indexPath];
    LKAsset* asset = [self.assetsCollection assetForIndexPath:indexPath];
    cell.imageView.image = asset.thumbnail;
    return cell;
}

Collection

LKAssetsCollection has a set of assets. It has an array of LKAssetsCollectionEntry, which has assets (LKAsset array).

Class diagram is here.

The intercae of LKAssetsCollection:

@interface LKAssetsCollection : NSObject

@property (nonatomic, weak  , readonly) LKAssetsGroup* group;
@property (nonatomic, strong, readonly) NSArray* entries;   // <lkassetscollectionentry>

@property (nonatomic, strong, readonly) id <LKAssetsCollectionGrouping> grouping;
@property (nonatomic, strong) id <LKAssetsCollectionFilter> filter;
@property (nonatomic, strong) id <LKAssetsCollectionSorter> sorter;

+ (instancetype)assetsCollectionWithGroup:(LKAssetsGroup*)group grouping:(id <LKAssetsCollectionGrouping>)grouping;

@end

@class LKAsset;
@interface LKAssetsCollection (NSIndexPath)
- (LKAsset*)assetForIndexPath:(NSIndexPath*)indexPath;
@end

The assets are extracted with 3 factors:

<LKAssetsCollectionGrouping>   Yearly, Monthly,...
<LKAssetsCollectionFilter>     JPEG, PNG, Screenshot,... 
<LKAssetsCollectionSorter>     Date in ascending or descending

These are defined as protocol. The library provides generic classes here.

LKAssetsCollectionGenericGrouping
LKAssetsCollectionGenericFilter
LKAssetsCollectionGenericSorter

You can use like below:

self.assetsCollection = [LKAssetsCollection assetsCollectionWithGroup:self.assetsGroup
                          grouping:[LKAssetsCollectionGenericGrouping groupingWithType:self.groupingType]];
self.assetsCollection.filter = [LKAssetsCollectionGenericFilter filterWithType:LKAssetsCollectionGenericFilterTypeJPEG|LKAssetsCollectionGenericFilterTypePNG];
self.assetsCollection.sorter = [LKAssetsCollectionGenericSorter sorterAscending:NO];

LKAssetsCollectionGrouping and LKAssetsGroup can not be changed, can be changed when initializing. LKAssetsFilter and LKAssetsSorter can be changed after initializing.

Demo

LKAssetsGroup's information are listed.

LKAssetsCollection's information are displayed. You can try various groupings, filters and sorters.

Requirements

iOS7

Author

Hiroshi Hashiguchi, [email protected]

License

LKAssetsLibrary is available under the MIT license. See the LICENSE file for more info.