design pattern
http://www.raywenderlich.com/46988/ios-design-patterns/
*NSKeyedUnarchiver can be used to save data.
-to save data:
NSMutableArray *albums;
albums = [NSMutableArray arrayWithArray:
@[[[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"]]];
NSString *filename = [NSHomeDirectory() stringByAppendingString:@"/Documents/albums.bin"];
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:albums];
[data writeToFile:filename atomically:YES];
-to read data:
NSData *data = [NSData dataWithContentsOfFile:[NSHomeDirectory() stringByAppendingString:@"/Documents/albums.bin"]];
albums = [NSKeyedUnarchiver unarchiveObjectWithData:data];
*when to set layout
note that the toolbar isn’t initiated with a frame, as the frame size set in viewDidLoad isn’t final. So set the final frame via the following block of code once the view frame is finalized by adding the code to
- (void)viewWillLayoutSubviews
{
toolbar.frame = CGRectMake(0, self.view.frame.size.height-44, self.view.frame.size.width, 44);
dataTable.frame = CGRectMake(0, 130, self.view.frame.size.width, self.view.frame.size.height - 200);
}
*how to remove all the subviews.
[scroller.subviews enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
[obj removeFromSuperview];
}];
*to save user data before the application entered background.
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveCurrentState) name:UIApplicationDidEnterBackgroundNotification object:nil];
- (void)saveCurrentState
{
[[NSUserDefaults standardUserDefaults] setInteger:currentAlbumIndex forKey:@"currentAlbumIndex"];
[[LibraryAPI sharedInstance] saveAlbums];
}
NOTE: need to call loadPreviousState from viewDidLoad()
*post notification
[[NSNotificationCenter defaultCenter] postNotificationName:@"BLDownloadImageNotification"
object:self
userInfo:@{@"imageView":coverImage, @"coverUrl":albumCover}];
*receive notification
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(downloadImage:) name:@"BLDownloadImageNotification" object:nil];
