What kind of category methods do you use to make Cocoa programming easier? - cocoa

Question

I use a collection of category methods for Cocoa's built in classes to make my life easier. I'll post some examples, but I really want to see what other coders have come up with. What kind of handy category methods are you using?
Example #1:
#implementation NSColor (MyCategories)
+ (NSColor *)colorWithCode:(long)code
{
return [NSColor colorWithCalibratedRed:((code & 0xFF000000) >> 24) / 255.0
green:((code & 0x00FF0000) >> 16) / 255.0
blue:((code & 0x0000FF00) >> 8) / 255.0
alpha:((code & 0x000000FF) ) / 255.0];
}
#end
// usage:
NSColor * someColor = [NSColor colorWithCode:0xABCDEFFF];
Example #2:
#implementation NSView (MyCategories)
- (id)addNewSubViewOfType:(Class)viewType inFrame:(NSRect)frame
{
id newView = [[viewType alloc] initWithFrame:frame];
[self addSubview:newView];
return [newView autorelease];
}
#end
// usage:
NSButton * myButton = [someView addNewSubviewOfType:[NSButton class]
inFrame:someRect];

Answer 1

I've really been loving Andy Matuschak's "KVO+Blocks" category on NSObject. (Yes, it adds some new classes internally as implementation details, but the end result is just a category on NSObject). It lets you provide a block to be executed when a KVO-conforming value changes rather than having to handle every KVO observation in the observeValueForKeyPath:ofObject:change:context: method.

Answer 2

Regular Expressions with RegexKitLite. Download # RegexKitLite-3.1.tar.bz2

Answer 3

Category, which adds md5/sha1 hashing to NSString. NSData one is similar.
#define COMMON_DIGEST_FOR_OPENSSL
#import <CommonCrypto/CommonDigest.h>
#implementation NSString(GNExtensions)
- (NSString*)
hashMD5
{
NSData* data = [self dataUsingEncoding: NSUTF8StringEncoding allowLossyConversion: NO];
unsigned char hashingBuffer[16];
char outputBuffer[32];
CC_MD5([data bytes], [data length], hashingBuffer);
for(int index = 0; index < 16; index++)
{
sprintf(&outputBuffer[2 * index], "%02x", hashingBuffer[index]);
}
return([NSString stringWithCString: outputBuffer length: 32]);
}
- (NSString*)
hashSHA1
{
NSData* data = [self dataUsingEncoding: NSUTF8StringEncoding allowLossyConversion: NO];
unsigned char hashingBuffer[20];
char outputBuffer[40];
CC_SHA1([data bytes], [data length], hashingBuffer);
for(int index = 0; index < 20; index++)
{
sprintf(&outputBuffer[2 * index], "%02x", hashingBuffer[index]);
}
return([NSString stringWithCString: outputBuffer length: 40]);
}
#end

Answer 4

I have a few nifty methods on NSDate. This is self-explanatory:
-(BOOL)isOnTheSameDayAsDate:(NSDate *)date {
NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *selfComponents = [cal components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit
fromDate:self];
NSDateComponents *dateComponents = [cal components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit
fromDate:date];
return (([selfComponents day] == [dateComponents day]) &&
([selfComponents month] == [dateComponents month]) &&
([selfComponents year] == [dateComponents year]));
}
Usage:
if ([aDate isOnTheSameDayAsDate:anotherDate]) { ... }
This provides a method to easily get dates like "9am the day before":
-(NSDate *)dateWithDayDelta:(NSInteger)daysBeforeOrAfter atHour:(NSUInteger)hour minute:(NSUInteger)minute second:(NSUInteger)second {
NSDate *date = [self addTimeInterval:(24 * 60 * 60) * daysBeforeOrAfter];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *comps = [calendar components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit |
NSMinuteCalendarUnit | NSSecondCalendarUnit
fromDate:date];
[comps setHour:hour];
[comps setMinute:minute];
[comps setSecond:second];
return [calendar dateFromComponents:comps];
}
Usage:
// We want 9am yesterday
NSDate *nineAmYesterday = [[NSDate date] dateWithDayDelta:-1
atHour:9
minute:0
second:0];