IOS: simulate a calendar

I have this code

NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
[components setYear:2011];
[components setDay:1];
[components setMonth:7];
NSCalendar *gregorianCalendar = [[[NSCalendar alloc]       initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *date = [gregorianCalendar dateFromComponents:components];
NSDateFormatter *dateFormatter = [[NSDateForm开发者_如何转开发atter alloc] init];
[dateFormatter setDateFormat:@"dd"];
NSString *strDate = [dateFormatter stringFromDate: date];

but now I want set 31 labels for each day of my month: how I can add this component for each label?

[components setDay:1];

and I also I want that all sundays are red, then avery 7 days label must be red color; can you help me?

Loops are your friend:

NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
[components setYear:2011];
[components setDay:1];
[components setMonth:7];
NSCalendar *gregorianCalendar = [[[NSCalendar alloc]       initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *firstDate = [gregorianCalendar dateFromComponents:components];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd"];

for (int i = 0; i < 31; i++) {
   NSTimeInterval seconds = 24*60*60 * i;
   NSDate *date = [NSDate dateWithTimeInterval:seconds sinceDate:firstDate];
   NSDateComponents *weekdayComponents = [gregorian components:NSWeekdayCalendarUnit fromDate:date];
   int weekday = [weekdayComponents weekday];
   NSString *strDate = [dateFormatter stringFromDate: date];
   yourLabel.text = strDate;
   yourLabel.textColor = weekday == 1 ? [UIColor redColor : blackColor];
}

Please adjust the yourLabel variable to the appropriate ones.

This is like @Eiko's answer, except more correct when dealing with things like daylight savings time, months that don't have 31 days, etc:

NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
[components setYear:2011];
[components setMonth:7];
[components setDay:1];

NSCalendar *gregorianCalendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *startDate = [gregorianCalendar dateFromComponents:components];
NSRange rangeOfDays = [gregorianCalendar rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:startDate];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd"];

for (NSInteger i = 1; i <= NSMaxRange(rangeOfDays); ++i) {
  [components setDay:i];
  NSDate *date = [gregorianCalendar dateFromComponents:components];

  yourLabel.text = [dateFormatter stringFromDate: date];

  NSDateComponents *weekdayComponents = [gregorian components:NSWeekdayCalendarUnit fromDate:date];
  int weekday = [weekdayComponents weekday];

  yourLabel.textColor = weekday == 1 ? [UIColor redColor : blackColor];
}

[dateFormatter release];