我怎样才能得到基金会的星期几？

NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateFormatter setDateFormat:@"EEEE"];
NSLog(@"%@", [dateFormatter stringFromDate:[NSDate date]]);

outputs current day of week as a string in locale dependent on current regional settings.

To get just a week day number you must use NSCalendar class:

NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *comps = [gregorian components:NSWeekdayCalendarUnit fromDate:[NSDate date]];
int weekday = [comps weekday];

Just use these three lines:

CFAbsoluteTime at = CFAbsoluteTimeGetCurrent();
CFTimeZoneRef tz = CFTimeZoneCopySystem();
SInt32 WeekdayNumber = CFAbsoluteTimeGetDayOfWeek(at, tz);

-(void)getdate {
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyy-MM-dd"];
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:@"MMM dd, yyyy HH:mm"];
NSDateFormatter *timeFormat = [[NSDateFormatter alloc] init];
[timeFormat setDateFormat:@"HH:mm:ss"];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init] ;
[dateFormatter setDateFormat:@"EEEE"];


NSDate *now = [[NSDate alloc] init];
NSString *dateString = [format stringFromDate:now];
NSString *theDate = [dateFormat stringFromDate:now];
NSString *theTime = [timeFormat stringFromDate:now];


NSString *week = [dateFormatter stringFromDate:now];
NSLog(@"\n"
"theDate: |%@| \n"
"theTime: |%@| \n"
"Now: |%@| \n"
"Week: |%@| \n"
, theDate, theTime,dateString,week);
}

Vladimir's answer worked well for me, but I thought that I would post the Unicode link for the date format strings.

http://www.unicode.org/reports/tr35/tr35-25.html#Date_Format_Patterns

This link is for iOS 6. The other versions of iOS have different standards which can be found in the X-Code documentation.

I needed a simple (Gregorian) day of the week index, where 0=Sunday and 6=Saturday to be used in pattern match algorithms. From there it is a simple matter of looking up the day name from an array using the index. Here is what I came up with that doesn't require date formatters, or NSCalendar or date component manipulation:

+(long)dayOfWeek:(NSDate *)anyDate {
//calculate number of days since reference date jan 1, 01
NSTimeInterval utcoffset = [[NSTimeZone localTimeZone] secondsFromGMT];
NSTimeInterval interval = ([anyDate timeIntervalSinceReferenceDate]+utcoffset)/(60.0*60.0*24.0);
//mod 7 the number of days to identify day index
long dayix=((long)interval+8) % 7;
return dayix;
}

This way it works in Swift:

    let calendar = NSCalendar.currentCalendar()
let weekday = calendar.component(.CalendarUnitWeekday, fromDate: NSDate())

Then assign the weekdays to the resulting numbers.

I had quite strange issue with getting a day of week. Only setting firstWeekday wasn't enough. It was also necesarry to set the time zone. My working solution was:

 NSCalendar* cal = [NSCalendar currentCalendar];
[cal setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[cal setFirstWeekday:1]; //Sunday
NSDateComponents* comp = [cal components:( NSWeekOfMonthCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit | NSWeekCalendarUnit)  fromDate:date];
return [comp weekday]  ;

Many of the answers here are deprecated. This works as of iOS 8.4 and gives you the day of the week as a string and as a number.

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"EEEE"];
NSLog(@"The day of the week: %@", [dateFormatter stringFromDate:[NSDate date]]);


NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *comps = [gregorian components:NSCalendarUnitWeekday fromDate:[NSDate date]];
int weekday = [comps weekday];
NSLog(@"The week day number: %d", weekday);

I think this topic is really useful, so I post some code Swift 2.1 compatible.

extension NSDate {


static func getBeautyToday() -> String {
let now = NSDate()
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "EEEE',' dd MMMM"
return dateFormatter.stringFromDate(now)
}


}

Anywhere you can call:

let today = NSDate.getBeautyToday()
print(today) ---> "Monday, 14 December"

Swift 3.0

As @delta2flat suggested, I update answer giving user the ability to specify custom format.

extension NSDate {


static func getBeautyToday(format: String = "EEEE',' dd MMMM") -> String {
let now = Date()
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = format
return dateFormatter.string(from: now)
}


}

Swift 2: Get day of week in one line. (based on neoscribe answer)

let dayOfWeek  = Int((myDate.timeIntervalSinceReferenceDate / (60.0*60.0*24.0)) % 7)
let isMonday   = (dayOfWeek == 0)
let isSunday   = (dayOfWeek == 6)

Here is the updated code for Swift 3

Code :

let calendar = Calendar(identifier: .gregorian)


let weekdayAsInteger = calendar.component(.weekday, from: Date())

To Print the name of the event as String:

 let dateFromat = DateFormatter()


datFormat.dateFormat = "EEEE"


let name = datFormat.string(from: Date())

Here's how you do it in Swift 3, and get a localised day name…

let dayNumber = Calendar.current.component(.weekday, from: Date()) // 1 - 7
let dayName = DateFormatter().weekdaySymbols[dayNumber - 1]

self.dateTimeFormatter = [[NSDateFormatter alloc] init];
self.dateTimeFormatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0]; // your timezone
self.dateTimeFormatter.locale = [NSLocale localeWithLocaleIdentifier:@"zh_CN"]; // your locale
self.dateTimeFormatter.dateFormat = @"ccc MM-dd mm:ss";

there are three symbols we can use to format day of week:

• E
• e
• c

The following two documents may help you.

https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/DataFormatting/Articles/dfDateFormatting10_4.html

http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns

Demo:

you can test your pattern on this website:

http://nsdateformatter.com/