ios - Core-Data NSFetchedResultsController to-many relationship -

here datamodel: datamodel http://s1.directupload.net/images/131007/ud8fqkra.png

i filled database data.

now want display in tableview. first want select day 'days' attribute, lessons. want display attributes 'end' , 'start' in header (-(nsstring *) tableview:(uitableview *)tableview titleforheaderinsection:(nsinteger)section)

then want display lesson data in right section. how can nsfetchedresultscontroller?

i've set basic code:

nsfetchrequest* fetch = [nsfetchrequest fetchrequestwithentityname:nsstringfromclass([lessons class])];  nssortdescriptor* sortgroup = [nssortdescriptor sortdescriptorwithkey:@"lesson" ascending:yes]; fetch.sortdescriptors = @[sortgroup];  nsfetchedresultscontroller *controller = [[nsfetchedresultscontroller alloc] initwithfetchrequest:fetch managedobjectcontext:self.managedobjectcontext sectionnamekeypath:nil cachename:nil];  nserror* error; [controller performfetch:&error]; if (error) {     nslog(@"error: %@", error);     abort(); } 

edit:

here storyboard:

update

here's code:

tableview.m (important methods)

-(id)init {     self = [super init];     if (self) {         nslog(@"%s",__pretty_function__);         self.del = [[uiapplication sharedapplication] delegate];         self.managedobjectcontext = self.del.managedobjectcontext;          nsfetchrequest* fetch = [nsfetchrequest fetchrequestwithentityname:@"lessons"];          nsstring *theselectedday = @"mi";          nspredicate *pred = [nspredicate predicatewithformat:@"lessontoday.day == %@", theselectedday];         fetch.predicate = pred;         nssortdescriptor *sorttime = [nssortdescriptor sortdescriptorwithkey:@"lessontotime.start" ascending:yes];         //nssortdescriptor *sortgroup = [nssortdescriptor sortdescriptorwithkey:@"lesson" ascending:yes];         fetch.sortdescriptors = @[sorttime];          self.controller = [[nsfetchedresultscontroller alloc] initwithfetchrequest:fetch                                                               managedobjectcontext:self.managedobjectcontext                                                                 sectionnamekeypath:@"lessontotime.start"                                                                          cachename:nil];     }     return self; }  #pragma mark - table view data source  - (nsinteger)numberofsectionsintableview:(uitableview *)tableview {     // return number of sections.     return 1; }  - (nsinteger)tableview:(uitableview *)tableview numberofrowsinsection:(nsinteger)section {     // return number of rows in section.     return 1; }  - (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {      static nsstring *cellidentifier = @"cell";       // configure cell...     //uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:cellidentifier];     uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:cellidentifier];     if (!cell) {         cell = [[uitableviewcell alloc] initwithstyle:uitableviewcellstyledefault reuseidentifier:cellidentifier];     }       lessons *lesson = [self.controller objectatindexpath:indexpath];     cell.textlabel.text = lesson.lesson;       return cell; }  - (nsstring *)tableview:(uitableview *)tableview titleforheaderinsection:(nsinteger)section {      id <nsfetchedresultssectioninfo> sectioninfo = [[self.controller sections] objectatindex:section];     // first lesson in section:     lessons *lesson = [sectioninfo objects][0];      //for testing changed type of 'start' , 'end' string     nslog(@"start: %@",lesson.lessontotime.start);     nslog(@"end: %@", lesson.lessontotime.end );      nsstring *title = [nsstring stringwithformat:@"%@-%@",                        lesson.lessontotime.start,                        lesson.lessontotime.end];     return title; } 

result:

first of have add predicate lessons selected day displayed:

nspredicate *pred = [nspredicate predicatewithformat:@"lessontoday.day == %@", theselectedday]; fetch.predicate = pred; 

to group table view sections, have set sectionnamekeypath: parameter of fetched results controller, example @"lessontotime.start". group lessons same start time 1 section. (as understand comment, lessons same start time have same end time, should sufficient.) same key path must used first sort descriptor:

nssortdescriptor *sorttime = [nssortdescriptor sortdescriptorwithkey:@"lessontotime.start" ascending:yes]; nssortdescriptor *sortgroup = [nssortdescriptor sortdescriptorwithkey:@"lesson" ascending:yes]; fetch.sortdescriptors = @[sorttime, sortgroup];  nsfetchedresultscontroller *controller = [[nsfetchedresultscontroller alloc] initwithfetchrequest:fetch             managedobjectcontext:self.managedobjectcontext             sectionnamekeypath:@"lessontotime.start"             cachename:nil]; 

to display section header according needs, have override titleforheaderinsection::

- (nsstring *)tableview:(uitableview *)tableview titleforheaderinsection:(nsinteger)section {      id <nsfetchedresultssectioninfo> sectioninfo = [[self.controller sections] objectatindex:section];     // first lesson in section:     lesson *lesson = [sectioninfo objects][0];     // build title lesson.lessontotime.start , lesson.lessontotime.end:     nsstring *title = ...;     return title; }