objective c - how to convert string value into date in iphone -

hi friend want convert string value date in project because fetching xml value web , in xml file weather condition , there value weather condition current date forecastcondition not come in date comes in string value friday saturday , sunday value come in forcast condition day string value come in day_of_week [day_of_week means shows friday,satarday,sunday ] want how can convert string value date please 1 me using please on controller class.m file

- (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {      tweathercell *cell =(tweathercell *) [mytableview dequeuereusablecellwithidentifier:[nsstring stringwithformat:@"cell_%d", indexpath.row]];     if (cell == nil) {         //cell = [[[tweathercell alloc] initwithstyle:uitableviewstylegrouped reuseidentifier:cellidentifier] autorelease];         cell = [[[tweathercell alloc] initwithframe:cgrectzero reuseidentifier:[nsstring stringwithformat:@"cell_%d", indexpath.row]] autorelease];     }         //forecastcondition *cond=[forecastcond objectatindex:0];     forecastcondition *cond1=[forecastcond objectatindex:1];     forecastcondition *cond2=[forecastcond objectatindex:2];     forecastcondition *cond3=[forecastcond objectatindex:3];      nsdate *today = [nsdate date]; // valid date, let's today thursdaya     nsdate *thursday = [today datewithtimeinterval:1 *one_day sincedate:cond1.dayofweek];     nsdate *friday = [today datewithtimeinterval:2 * one_day sincedate:cond2.dayofweek];     nsdate *saturday = [today datewithtimeinterval:3 * one_day sincedate:cond3.dayofweek];     if ([currentcond.icon isequaltostring:@"http://\n"])     {         cell.weatherimage.image = [uiimage imagenamed:@"listicon-h.png"];     }     else {     nsdata *imagedata = [[nsdata alloc]initwithcontentsofurl:[nsurl urlwithstring:currentcond.icon]];                nslog(@"this image server:%@",imagedata);         cell.weatherimage.image = [uiimage imagewithdata:imagedata];         [imagedata release];     }     nsdateformatter *date_formatter=[[nsdateformatter alloc]init];      [date_formatter setdateformat:@"dd-mm-yyyy"];      switch (indexpath.row) {         case 0:     nslog(@"%d",indexpath.row);             nsdata *imagedata = [[nsdata alloc]initwithcontentsofurl:[nsurl urlwithstring:currentcond.icon]];             nslog(@"this image server:%@",imagedata);             cell.weatherimage.image = [uiimage imagewithdata:imagedata];             [imagedata release];      cell.reportdate.text = _forecastinfo.currentdatetime;     cell.conditionname.text = currentcond.condition;     cell.twotemp.text = [nsstring stringwithformat:@"temp:%@/%@",currentcond.tempf,currentcond.tempf];     cell.twodirection.text = currentcond.windcondition;     cell.humidity.text = currentcond.humidity;      break;         case 1:             nslog(@"%d",indexpath.row);              cell.reportdate.text = cond1.dayofweek;             cell.conditionname.text = cond1.condition;             cell.twotemp.text = [nsstring stringwithformat:@"temp:%@/%@",cond1.low,cond1.high];             //nsdateformatter *date_formatter=[[nsdateformatter alloc]init];  //          [date_formatter setdateformat:@"dd-mm-yyyy"];               //[cond.dayofweek datewithtimeintervalsincenow:(60*60*24)*1];             //nsdate *date1 = [date_formatter datefromstring:cond.dayofweek];              //nsdate *= nsdate *date1 ;             //nsdate *date1 = [nsdate date];             //nsstring *strdate = [date_formatter stringfromdate:date1];                break;         case 2:              nslog(@"%d",indexpath.row);             cell.reportdate.text = cond2.dayofweek;             cell.conditionname.text = cond2.condition;             cell.twotemp.text = [nsstring stringwithformat:@"temp:%@/%@",cond2.low,cond2.high];             break;         case 3:             nslog(@"%d",indexpath.row);             cell.reportdate.text = cond3.dayofweek;             cell.conditionname.text = cond3.condition;             cell.twotemp.text = [nsstring stringwithformat:@"temp:%@/%@",cond3.low,cond3.high];             break;         default:             nslog(@"out of range ",indexpath.row);             break;     }     return cell; } 

i gather problem future dates coming in "thursday", "friday", ...?

basically, need convert text day-of-week number (simplest approach "if ladder", though if want locale-sensitive can use more complex scheme). figure out today's day-of-week number , subtract first number. if result negative, add 7. (if result zero, may mean refers today, or may mean refers week today -- if want latter, add 7 if result zero or negative.) then, compute date represented input day of week, add above computed result multiplied times one_day current date.

more detail

you know "if ladder" is, of course:

if ([day isequaltostring:@"sunday"]) {     daynumber = 1; } else if ([day isequaltostring:@"monday"]) {     daynumber = 2; } else if ([day isequaltostring:@"tuesday"]) { .... 

to day of week current date use like:

nscalendar *gregorian = [[nscalendar alloc] initwithcalendaridentifier:nsgregoriancalendar]; nsdatecomponents *components = [gregorian components:nsweekdaycalendarunit fromdate:today]; nsinteger todaynumber = [components weekday]; 

subtract todaynumber daynumber. if result negative, add 7 result. value tells how many days in future "day" is, , can calculate it's date.