gistfile1.m

@implementation NSArray (NSArray+MyAdditions)

- (NSArray *)arrayOfClass:(Class)class {
	
	 // oh look, dictionaries..
}


@implementation NSObject (NSObject+MyAdditions)

- (id)initWithDictionary:(NSDictionary *)dictionary {
	
	self = [super init];
	if (self == nil) {
		return nil;
	}
    
        [self setValuesForKeysWithDictionary:dictionary];
    
        return self;
}

@end

@implementation MyModelObject

- (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues {
	
	self.propertyName = [keyedValues valueForKey:@"underscore_bullshit"];
	// etc..
}

// thanks @bmf!

@end