swift - NSFetchedResultsController different sort descriptors for each section -

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i have objects nsdate property , need split them 2 sections (first - future events, second - historic events) , first section need sort them date property in ascending order , second section in descending order. idea how sorting?

assuming using nsfetchedresultscontroller, underlying fetch must sorted 1 way or other. can think of 2 different solutions:

  1. use 2 separate frcs, complementary predicates 1 handles past events, while other handles future events. 1 sorted ascending, other descending. problem both frcs generate indexpaths section 0. therefore need remap second frc's indexpaths use section 1 of tableview. example, in cellforrowatindexpath need this:

    if (indexpath.section == 0) {     objecttodisplay = self.futurefetchedresultscontroller.objectatindexpath(indexpath) } else { // use second frc     let frcindexpath = nsindexpath(forrow: indexpath.row, insection: 0)     objecttodisplay = self.pastfetchedresultscontroller.objectatindexpath(frcindexpath) }

  2. alternatively, stick single frc, sorted ascending. remap indexpath second section, last object in section displayed in row 0, etc:

    if (indexpath.section == 0) {     objecttodisplay = self.fetchedresultscontroller.objectatindexpath(indexpath) } else { // use remap reverse sort order frc     let sectioninfo = self.fetchedresultscontroller.sections[1] as! nsfetchedresultssectioninfo     let sectioncount = sectioninfo.numberofobjects     let frcindexpath = nsindexpath(forrow: (sectioncount - 1 - indexpath.row), insection:indexpath.section)     objecttodisplay = self.fetchedresultscontroller.objectatindexpath(frcindexpath) }

personally think second option preferable. in each case, tableview datasource/delegate methods need same remapping, , frc delegate methods need reverse mapping.


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