Classes/DataSource.m

/*
     File: DataSource.m
 Abstract: The singular data source for the table view controller
  Version: 1.1
 
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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
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 */
 
#import "DataSource.h"
 
@interface DataSource ()
@property (nonatomic, strong) NSMutableArray *dataArray;
@end
 
@implementation DataSource
 
+ (DataSource *)sharedInstance
{
    static dispatch_once_t  onceToken;
    static DataSource * sSharedInstance;
    
    dispatch_once(&onceToken, ^{
        sSharedInstance = [[DataSource alloc] init];
    });
    return sSharedInstance;
}
 
// returns the URL to the application's Documents directory
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
 
- (id)init
{
    self = [super init];
    if (self != nil)
    {
        NSURL *dataFileURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"SavedData"];
        if ([[NSFileManager defaultManager] fileExistsAtPath:[dataFileURL path]])
        {
            // saved file exists, load it's content from that path
            // note: unarchiveObjectWithFile returns an immutable array, we need to make it mutable
            //
            _dataArray = [[NSKeyedUnarchiver unarchiveObjectWithFile:[dataFileURL path]] mutableCopy];
        }
        else
        {
            _dataArray = [[NSMutableArray alloc] init];
        }
    }
    return self;
}
 
- (NSInteger)count
{
    return self.dataArray.count;
}
 
- (void)addItem:(Item *)item
{
    [self.dataArray addObject:item];
}
 
- (Item *)itemAtIndex:(NSInteger)index
{
    return [self.dataArray objectAtIndex:index];
}
 
- (void)removeItemAtIndex:(NSInteger)index
{
    [self.dataArray removeObjectAtIndex:index];
}
 
- (void)insertItem:(Item *)item atIndex:(NSInteger)index;
{
    [self.dataArray insertObject:item atIndex:index];
}
 
- (void)replaceItemAtIndex:(NSInteger)index withObject:(Item *)item
{
    [self.dataArray replaceObjectAtIndex:index withObject:item];
}
 
- (Item *)itemWithIdentifier:(NSString *)identifier
{
    return [self.dataArray objectAtIndex:[self.dataArray indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
        *stop = [[obj identifier] isEqual:identifier];
        return *stop;
    }]];
}
 
- (NSIndexPath *)indexPathForItem:(Item *)item
{
    return [NSIndexPath indexPathForRow:[self.dataArray indexOfObject:item] inSection:0];
}
 
- (void)save
{
    NSURL *dataFileURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"SavedData"];
    [NSKeyedArchiver archiveRootObject:self.dataArray toFile:[dataFileURL path]];
}
 
@end