Ignore touches to UIView subclass, but not to its subviews

Note: I’ve moved all future technical/programming posts out of this blog and over to objectivesea.tumblr.com. Follow that one if you’re going to follow me for technical junk.

If you want a UIView subclass to ignore touch events, just set its userInteractionEnabled property to NO. But that will block touches to all its subviews. To ignore touches in a UIView subclass, but not its subviews, just work a little hitTest magic:

-(id)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    id hitView = [super hitTest:point withEvent:event];
    if (hitView == self) return nil;
    else return hitView;
}

How to set default values for NSUserDefaults

NSUserDefaults is a great place to store your apps settings. It is convenient, available everywhere, and integrates nicely with settings bundles. One problem you run across with NSUserDefaults, is setting default values for your settings. There is a very simple elegant solution to this, detailed below.

Define keys

I usually have one header file just for keys I use throughout the project.

Create a defaults property list

Create a new property list, and enter default values for all your settings. Make sure the keys match the ones you #define-d. Also pay attention to the types.

Set defaults on launch

The following code needs to run every time your app launches (in case your NSUserDefaults have gotten nuked or mangled). I added the following three lines to application:didFinishLaunchingWithOptions: in my app delegate.

NSString *defPath = [[NSBundle mainBundle] pathForResource:@"DEF" ofType:@"plist"];

NSDictionary *defaultsDict = [NSDictionary dictionaryWithContentsOfFile:defPath];

[[NSUserDefaults standardUserDefaults] registerDefaults:defaultsDict];

Fantastic, you are done.

NSDateFormatter format strings for Twitter and Facebook

Format strings for processing dates from facebook or twitter’s json api’s

//2010-09-12T22:21:18+0000
#define DF_FACEBOOK @"yyyy-MM-dd'T'HH:mm:ssZZ"
// Sun Sep 12 17:06:56 +0000 2010
#define DF_TWITTER @"EEE LLL dd HH:mm:ss ZZ yyyy"

Usage:

NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setTimeStyle:NSDateFormatterFullStyle]; // important
[df setDateFormat:DF_TWITTER];
NSDate *date = [df dateFromString:dateStringTwitter];
[df release];

Where DF_TWITTER would be DF_FACEBOOK, if you were processing facebook json instead of Twitter.

How to vertically center a UITextView

Note: I’ve moved all future technical/programming posts out of this blog and over to objectivesea.tumblr.com. Follow that one if you’re going to follow me for technical junk.

This took me ages to figure out how to vertically center the text in a UITextView. There really ought to be a property to set, but there isn’t so… this is pretty easy.

In -(void)viewDidLoad, add this to observe the contentSize key value:

[textView addObserver:self forKeyPath:@"contentSize" options:(NSKeyValueObservingOptionNew) context:NULL];

Then add this method, which adjusts the contentOffset every time the contentSize value changes.

-(void)observeValueForKeyPath:(NSString *)keyPath   ofObject:(id)object   change:(NSDictionary *)change   context:(void *)context {
 UITextView *tv = object;
 CGFloat topCorrect = ([tv bounds].size.height - [tv contentSize].height * [tv zoomScale])  / 2.0;
 topCorrect = ( topCorrect < 0.0 ? 0.0 : topCorrect );
 tv.contentOffset = (CGPoint){.x = 0, .y = -topCorrect};
}

Et voila!

FileMaker Custom Function: Hex to Decimal

This FileMaker Pro Custom Function converts a single character from hex to decimal.

I’m using it to convert an HTML-style hex colour into decimal, and then floating point values. I grab two characters from the string, pass each one to the function, and then divide the result by 30. The first two characters represent red, second two green, last two are the blue.

Function name: HexToDec

Function parameters: hexCharacter

Let (a = Upper ( Left(hexCharacter; 1) ); 
Case (
a = "0"; 0;
a = "1"; 1;
a = "2"; 2;
a = "3"; 3;
a = "4"; 4;
a = "5"; 5;
a = "6"; 6;
a = "7"; 7;
a = "8"; 8;
a = "9"; 9;
a = "A"; 10;
a = "B"; 11;
a = "C"; 12;
a = "D"; 13;
a = "E"; 14;
a = "F"; 15;0)
)