ios - How to properly sort an NSDictonary by key values that contain strings of time? -

i'm not understanding why it's not sorting properly. have nsdictionary contains key values of times in day. when try sort it, it's not ordered.

events = @{@"12:00 pm" : @[@"1"],            @"12:30 pm" : @[@"2"],            @"1:00 pm" : @[@"3", @"4"],            @"1:30 pm" : @[@"5", @"11"],            @"2:00 pm" : @[@"6"],            @"3:00 pm" : @[@"7"],            @"3:30 pm" : @[@"8"],            @"4:00 pm" : @[@"9"],            @"4:30 pm" : @[@"10", @"11"],            @"5:00 pm" : @[@"12", @"13", @"14"]};  eventtimes = [ [events allkeys] sortedarrayusingselector:@selector(localizedcaseinsensitivecompare:)]; 

when nslog eventtimes, produces output:

( "1:00 pm", "1:30 pm", "12:00 pm", "12:30 pm", "2:00 pm", "3:00 pm", "3:30 pm", "4:00 pm", "4:30 pm", "5:00 pm" )

how can achieve output?

( "12:00 pm", "12:30 pm", "1:00 pm", "1:30 pm", "2:00 pm", "3:00 pm", "3:30 pm", "4:00 pm", "4:30 pm", "5:00 pm" )

update: tried:

nsdateformatter *formatter = [[nsdateformatter alloc] init]; [formatter setlocale:[[nslocale alloc] initwithlocaleidentifier:@"en_us"] ]; [formatter setdateformat:@"hh:mm"]; nsstring *etastr = [eventtimes objectatindex:section]; nsdate *generateddate = [formatter datefromstring:etastr]; nslog(@"%@", [formatter stringfromdate:generateddate]); 

however, nil.

1. keep time number of seconds, timestamp or nsdate.
2. use regular sort.
3. use nsdateformatter produce time string in preferred format. keep application data in format friendly internal data organization , formatting before display on screen.

regarding nsdateformatter questions , how convert time string nsdate, played around in playground , seems key set shortstyle format time, setup en_us locale since convert 12h time , make sure use utc timezone avoid time offset because time absolute anyway.

// playground - noun: place people can play  import uikit  // input var times = [     "3:30 pm", "4:00 pm", "4:30 pm",     "5:00 pm", "12:30 pm", "12:00 pm",     "1:00 pm", "1:30 pm", "2:00 pm",     "3:00 pm" ]  // create array of nsdate objects var dates = nsmutablearray()  println("convert time string nsdate") println()  // setup formatter time style let formatter = nsdateformatter() formatter.dateformat = "h:mm a" formatter.datestyle = nsdateformatterstyle.nostyle formatter.timestyle = nsdateformatterstyle.shortstyle formatter.timezone = nstimezone(name: "utc") formatter.locale = nslocale(localeidentifier: "en_us")  // loop thru input data , convert time string nsdate t in times {     let date = formatter.datefromstring(t)      dates.addobject(date!)      println("t = \(t) converted \(date)") }  println() println("sort array of nsdate objects") println()  // sort dates let sorteddates = dates.sortedarrayusingdescriptors([ nssortdescriptor(key: "self", ascending: true) ])  // print out sorted array of dates d in sorteddates {     let date = d nsdate     let formattedstring = formatter.stringfromdate(date)     println("\(formattedstring)") } 

now of in swift sure it's intuitive enough write same code in objective-c.

the console output:

convert time string nsdate  t = 3:30 pm converted optional(2000-01-01 15:30:00 +0000) t = 4:00 pm converted optional(2000-01-01 16:00:00 +0000) t = 4:30 pm converted optional(2000-01-01 16:30:00 +0000) t = 5:00 pm converted optional(2000-01-01 17:00:00 +0000) t = 12:30 pm converted optional(2000-01-01 12:30:00 +0000) t = 12:00 pm converted optional(2000-01-01 12:00:00 +0000) t = 1:00 pm converted optional(2000-01-01 13:00:00 +0000) t = 1:30 pm converted optional(2000-01-01 13:30:00 +0000) t = 2:00 pm converted optional(2000-01-01 14:00:00 +0000) t = 3:00 pm converted optional(2000-01-01 15:00:00 +0000)  sort array of nsdate objects  12:00 pm 12:30 pm 1:00 pm 1:30 pm 2:00 pm 3:00 pm 3:30 pm 4:00 pm 4:30 pm 5:00 pm