IOS设计模式之一（MVC模式，单例模式）

 

@property (nonatomic, copy, readonly) NSString *title, *artist, *genre, *coverUrl, *year;  
- (id)initWithTitle:(NSString*)title artist:(NSString*)artist coverUrl:(NSString*)coverUrl year:(NSString*)year;

- (id)initWithTitle:(NSString*)title artist:(NSString*)artist coverUrl:(NSString*)coverUrl
  year:(NSString*)year {
    self = [super init];
    if (self)
    {
        _title = title;
        _artist = artist;
        _coverUrl = coverUrl;
        _year = year;
        _genre = @"Pop";
    }
    return self;
}

- (id)initWithFrame:(CGRect)frame   albumCover:(NSString*)albumCover;

@implementationAlbumView
{
    UIImageView *coverImage;
    UIActivityIndicatorView *indicator;
}
 
- (id)initWithFrame:(CGRect)frame albumCover:(NSString*)albumCover
{
    self = [super initWithFrame:frame];
    if (self)
    {
 
        self.backgroundColor = [UIColor blackColor];
        // the coverImage has a 5 pixels margin from its frame
        coverImage = [[UIImageView alloc] initWithFrame:CGRectMake(5, 5, frame.size.width-10,
 
        frame.size.height-10)];
        [self addSubview:coverImage];
 
        indicator = [[UIActivityIndicatorView alloc] init];
        indicator.center = self.center;
        indicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
        [indicator startAnimating];
        [self addSubview:indicator];
    }
    return self;
}
 
@end

 

 

 

 

@interfaceLibraryAPI : NSObject
 
+ (LibraryAPI*)sharedInstance;
 
@end

+ (LibraryAPI*)sharedInstance
{
    // 1
    static LibraryAPI *_sharedInstance = nil;
 
    // 2
    static dispatch_once_t oncePredicate;
 
    // 3
    dispatch_once(&oncePredicate, ^{
        _sharedInstance = [[LibraryAPI alloc] init];
    });
    return _sharedInstance;
}

- (NSArray*)getAlbums;
- (void)addAlbum:(Album*)album atIndex:(int)index;
- (void)deleteAlbumAtIndex:(int)index;

@interfacePersistencyManager () {
    // an array of all albums
    NSMutableArray *albums;
}

- (id)init
{
    self = [super init];
    if (self) {
        // a dummy list of albums
        albums = [NSMutableArrayarrayWithArray:
                 @[[[Album alloc] initWithTitle:@"Best of Bowie" artist:@"David Bowie" coverUrl:@"http://www.coversproject.com/static/thumbs/album/album_david%20bowie_best%20of%20bowie.png" year:@"1992"],
                 [[Album alloc] initWithTitle:@"It's My Life" artist:@"No Doubt" coverUrl:@"http://www.coversproject.com/static/thumbs/album/album_no%20doubt_its%20my%20life%20%20bathwater.png" year:@"2003"],
                 [[Album alloc] initWithTitle:@"Nothing Like The Sun" artist:@"Sting" coverUrl:@"http://www.coversproject.com/static/thumbs/album/album_sting_nothing%20like%20the%20sun.png" year:@"1999"],
                 [[Album alloc] initWithTitle:@"Staring at the Sun" artist:@"U2" coverUrl:@"http://www.coversproject.com/static/thumbs/album/album_u2_staring%20at%20the%20sun.png" year:@"2000"],
                 [[Album alloc] initWithTitle:@"American Pie" artist:@"Madonna" coverUrl:@"http://www.coversproject.com/static/thumbs/album/album_madonna_american%20pie.png" year:@"2000"]]];
    }
    return self;
}

- (NSArray*)getAlbums
{
    return albums;
}
 
- (void)addAlbum:(Album*)album atIndex:(int)index
{
    if (albums.count >= index)
        [albums insertObject:album atIndex:index];
    else
        [albums addObject:album];
}
 
- (void)deleteAlbumAtIndex:(int)index
{
    [albums removeObjectAtIndex:index];
}