ios - Swift Problems understanding the result of Calendar.dateComponents -


in app have list of contacts including contacts birthday. want see of contacts have birthday within in next 7 days. using filter on list filter , return thos contacts match

     let timespan = 7      let cal = calendar.current      let = date()      var birthdays = contactlist.filter { (contact) -> bool in         if let birthdate = contact.birthdate {             let difference = cal.datecomponents([.day,.year], from: birthdate date, to: now! )             print("bd:\(birthdate) : diff \(difference.day!)")             return ((difference.day! <= timespan) && difference.day! >= 0)         }         return false     }

my hope so. result weired. added ugly print closure in order see result of 'difference'

what odd instance following: today 2017-08-18 1 of contacts born on 1987-08-19. instead of returning difference.day of 1 receive 364. if swap from: , to: in datecomponents receive difference.day of -364.

my expectation have difference.day = 1.

again in playground

import uikit var = date() let dateformatter = dateformatter()  dateformatter.dateformat = "yyyy-mm-dd" let s = dateformatter.date(from: "1987-08-19")  let cal = calendar.current  let difference = cal.datecomponents([calendar.component.day,calendar.component.month,calendar.component.year], from: s!, to: ) print("\(difference.day!)") // result difference.day = 30

what doing wrong?

thanks

you can create extension return number of days next birthday follow:

extension date {     var year:  int { return calendar.current.component(.year, from: self)  }     var month: int { return calendar.current.component(.month, from: self) }     var day:   int { return calendar.current.component(.day, from: self)   }     var noon: date { return calendar.current.date(bysettinghour: 12, minute: 0, second: 0, of: self)! }     var daysfrombirthday: int {         let nextbirthdate = datecomponents(calendar: .current, year: date().year + (month < date().month ? 1 : 0), month: month, day: day, hour: 12).date ?? date.distantfuture         return calendar.current.datecomponents([.day], from: date().noon, to: nextbirthdate).day ?? 0     } }

and can filter objects follow:

let timespan = 0...7  let birthdays = contactlist.filter {     timespan ~= $0.birthdate?.daysfrombirthday ?? -1 }

Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj...
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer ...
Read more

c# - Asp.net web api : redirect unauthorized requst to forbidden page -

im trying redirect unauthorized request forbidden page instead i'm getting forbidden page in response body , how can fix ? here's startup class : app.createperowincontext(storecontext.create); app.createperowincontext<applicationusermanager>(applicationusermanager.create); app.createperowincontext<applicationsigninmanager>(applicationsigninmanager.create); app.usecookieauthentication(new cookieauthenticationoptions { authenticationtype = defaultauthenticationtypes.applicationcookie, expiretimespan = timespan.fromdays(30), }); app.useexternalsignincookie(defaultauthenticationtypes.externalcookie); app.usetwofactorsignincookie(defaultauthenticationtypes.twofactorcookie, timespan.fromminutes(5)); app.usetwofactorrememberbrowsercookie(defaultauthenticationtypes.twofactorrememberbrowsercookie); the method im trying reach : [httpget] [authorize(roles = "admin")] public string getcurrentusername() { return userman...
Read more