Convert NSDate to an Integer

问题

So my dilemma is that I can't figure out how to store the date only in an integer value (fetched using:

NSDate* date = [NSDate date]

I found this code online which seems similar to what I need (I thought that changing setDateFormat to @"dd" would've worked (but apparently it didn't)

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy"];

//Optionally for time zone conversions
[formatter setTimeZone:[NSTimeZone timeZoneWithName:@"..."]];

NSString *stringFromDate = [formatter stringFromDate:date];

Am I just forgetting something simple about integers?

回答1:

Use dd in setDateFormat:.

This will give only date but in string.

After this you can convert the string to integer, with the help of integerValue.

Edit:

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


NSString *stringFromDate = [formatter stringFromDate:[NSDate date]];
NSInteger integerDate = [stringFromDate integerValue];

回答2:

Swift

NSDate to Int

// using current date and time as an example
let someNSDate = NSDate() 

// convert NSDate to NSTimeInterval (typealias for Double)
let timeInterval = someNSDate.timeIntervalSince1970

// convert to Integer
let myInt = Int(timeInterval)

Doing the Double to Int conversion causes the milliseconds to be lost. If you need the milliseconds then multiply by 1000 before converting to Int.

Int to NSDate

Including the reverse for completeness.

// convert Int to Double
let timeInterval = Double(myInt)

// create NSDate from Double (NSTimeInterval)
let myNSDate = NSDate(timeIntervalSince1970: timeInterval)

I could have also used timeIntervalSinceReferenceDate instead of timeIntervalSince1970 as long as I was consistent. This is assuming that the time interval is in seconds. Note that Java uses milliseconds.

Update

As of Swift 3, the conversion would use Date rather than NSDate. See this answer for the Swift 3 version.

回答3:

Although I believe the original poster was looking for just the 'days' part of the date, I imagine that given the title, others will come to this question looking for a way to convert a date to a canonical integer representation (for example, milliseconds since the epoch).

The Cocoa date library stores dates as a floating point number of seconds since 00:00:00 UTC on 1 January 2001.

To get this value, call [NSDate timeIntervalSinceReferenceDate]. To get the number of seconds (floating point) since the Unix epoch, call [NSDate timeIntervalSince1970]. To get milliseconds, simply multiply by 1000.

So, to get the number of milliseconds since the Unix epoch, as an integer:

(NSInteger)round([NSDate timeIntervalSince1970] * 1000)

来源：https://stackoverflow.com/questions/27059292/convert-nsdate-to-an-integer