n o t e 1 9 . c o m

I’ve recently started using my iPhone to read reference books. I bought a number of books on Amazon, but the Kindle app is kind of annoying for reference material. For example, there is no search, you cant jump to the Index section, the table of content is just a long list of long links making it difficult to scroll through the TOC pages. But there is a new class of reference material for the iPhone that take advantage of the native iPhone controls to provide a much more enjoyable and useful experience. By far the best such apps that I’ve seen to date are SDK IQ by cygen.com, 7-Steps to a successful Startup by Naeem Zafar, and Presenter Pro app.

Today I had to migrate a MySQL table to SQLite so that I could use it in an iPhone app. The process is simple, you can export the MySQL table and then import it in SQLite. I found the following shell script in the MySQL site (I think), but the resulting file could not be imported in SQLite, since I had used the MySQL COMMENT to document each of the columns. SQLite does not understand column comments. So here is the updated script that makes the MYSQL dump work with SQLite.

#!/bin/sh 

/opt/local/lib/mysql5/bin/mysqldump --compact --compatible=ansi --default-character-set=binary -uUSERNAME -pPASSWORD DATABASE TABLE  | 
sed -e "s/COMMENT '.*',/,/" |
grep -v ' KEY "' | 
grep -v ' UNIQUE KEY "' | 
perl -e 'local $/;$_=<>;s/,\n\)/\n\)/gs;print "begin;\n";print;print "commit;\n"' | 
perl -pe ' 
if (/^(INSERT.+?)\(/) { 
$a=$1; 
s/\\'\''/'\'\''/g; 
s/\\n/\n/g; 
s/\),\(/\);\n$a\(/g; 
} 
' > db.sql 

You must substitute the USERNAME, PASSWORD, DATABASE and TABLE with the values for your project.

Next, you need to load this dump file into SQLite, issue the following command:

cat db.sql | sqlite3 db.db

This will create a SQLite database in a file called db.db. Now you can add the file db.db to your iPhone project, plus add the SQLite3 iphone framework and finally you’ll be ready to use the database from Objective-C.

There are times when you want to add a UITableView to a UIViewController (without having to use a UITableViewController). To do this, you’ve to make sure to override the implementation of a number of methods in the delegate and data source classes to get the table to work as expected, i.e., to support deletion and insertion of rows. You’ve to remember to make the following changes:

You need to implement some of the methods of the UITableViewDelegate and UITableViewDataSource classes. Don’t forget to declare them in the interface definition. If you’re using the Interface Builder, make sure that you connect the table view to my_table. I forgot to do this step causing much frustration. If you forget this step, the table view object is not created, but calling methods on it don’t fail so you don’t have a easy null pointer exception to help you find the cause.
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To tile an image on a UIImageView, you’ll need to use CGContextDrawTiledImage function. Here is a code snippet to tile an image called wave on the imageView object that you’ve defined.

- (void)viewDidLoad {
        [super viewDidLoad];
	
	UIImage *wave = [UIImage imageNamed:@"wave-bg.png"];
	CGSize imageViewSize = imageView.bounds.size;
	
	UIGraphicsBeginImageContext(imageViewSize);

	CGRect imageRect;
	imageRect.origin = CGPointMake(0.0, 0.0);
	imageRect.size = CGSizeMake(wave.size.width, wave.size.height);
	
	CGContextRef imageContext = UIGraphicsGetCurrentContext();
	CGContextDrawTiledImage(imageContext, imageRect, wave.CGImage);

	UIImage *finishedImage = UIGraphicsGetImageFromCurrentImageContext();
	
	UIGraphicsEndImageContext();
	
	imageView.image = finishedImage;
}

In an iPhone application where can you store the model (MVC) object and how do you share it between view controllers? There are a number of ways for doing this. I found the easiest way is to define the model object in the application delegate class and use the UIApplication sharedApplication singleton object from any view controller to access the model.

In your application delegate class define the model. Here the model is assumed to be an NSMutableArray object. Declare the model in the application delegate header file and the define it in the application delegate .m file.

...
@interface MyAppDelegate : NSObject <UIApplicationDelegate> 
{
	UIWindow *window;
        ...
	NSMutableArray *the_model;
}

@property (nonatomic, retain) NSMutableArray *the_model;
...
@end

Now you can access this model in any of your view controllers:

MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
NSMutableArray *model = appDelegate.the_model;