Sort UITableView into sections by date from Array of events

Question

I've retrieved data from 2 different shared Google Calendars, and stored the data in an array. I need to sort the data into a sectioned UITableView, sorted by date.

Heres my code:

CalendarModel.h

#import "JSONModel.h"
#import "Time.h"

@interface CalendarModel : JSONModel

@property (strong, nonatomic) NSString* title;
@property (strong, nonatomic) NSArray<Time>* time;

@end

CalendarModel.m

#import "CalendarModel.h"

@implementation CalendarModel


+(JSONKeyMapper*)keyMapper
{
    return [[JSONKeyMapper alloc] initWithDictionary:@{
            @"gd$when": @"time",
            @"title.$t": @"title",
            }];
}

@end

Time.h

#import "JSONModel.h"

@protocol Time @end

@interface Time : JSONModel

@property (strong, nonatomic) NSString* startTime;
@property (strong, nonatomic) NSString* endTime;

@end

Time.m does nothing, as it's handled by JSONModel

SportsViewController.m

#import "SportsViewController.h"
#import "JSONModelLib.h"
#import "CalendarModel.h"
#import "Time.h"
#import "JSONValueTransformer.h"

@interface SportsViewController () 

@property (strong, nonatomic) NSMutableArray *events;
@property (strong, nonatomic) NSArray *music;

- (NSDate *)dateAtBeginningOfDayForDate:(NSDate *)inputDate;
- (NSDate *)dateByAddingYears:(NSInteger)numberOfYears toDate:(NSDate *)inputDate;

@end

@implementation SportsViewController

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    //make HTTP call
    NSString* searchCall = [NSString stringWithFormat:@"http://www.google.com/calendar/feeds/kao1d80fd2u5kh7268caop11o4%%40group.calendar.google.com/public/full?alt=json"];
    NSString* searchCall2 = [NSString stringWithFormat:@"http://www.google.com/calendar/feeds/3qag5m8iad46mtvsnnqbtrcjjg%%40group.calendar.google.com/public/full?alt=json"];

    [JSONHTTPClient getJSONFromURLWithString: searchCall
                                  completion:^(NSDictionary *json, JSONModelError *err) {

                                      //got JSON back
                                      NSLog(@"Got Sports JSON from web: %@", json);

                                      if (err) {
                                          [[[UIAlertView alloc] initWithTitle:@"Error"
                                                                      message:[err localizedDescription]
                                                                     delegate:nil
                                                            cancelButtonTitle:@"Close"
                                                            otherButtonTitles: nil] show];
                                          return;
                                      }

                                      //initialize the models
                                      _events = [CalendarModel arrayOfModelsFromDictionaries:
                                                json[@"feed"][@"entry"]
                                                ];

                                      if (_events) NSLog(@"Loaded successfully sports models");

                                      //show the Events
                                      [_events addObjectsFromArray:_music];
                                      NSLog(@"%@", _events);
                                      [self.tableView reloadData];

                                  }];

    [JSONHTTPClient getJSONFromURLWithString: searchCall2
                                  completion:^(NSDictionary *json2, JSONModelError *err2) {

                                      //got JSON back
                                      NSLog(@"Got Music JSON from web: %@", json2);

                                      if (err2) {
                                          [[[UIAlertView alloc] initWithTitle:@"Error"
                                                                      message:[err2 localizedDescription]
                                                                     delegate:nil
                                                            cancelButtonTitle:@"Close"
                                                            otherButtonTitles: nil] show];
                                          return;
                                      }

                                      //initialize the models
                                      _music = [CalendarModel arrayOfModelsFromDictionaries:
                                                json2[@"feed"][@"entry"]
                                                ];

                                      if (_music) NSLog(@"Loaded successfully music models");
                                      [_events addObjectsFromArray:_music];
                                      //show the Events
                                      [self.tableView reloadData];

                                  }];
    //[events addObjectsFromArray:music];
    [self.tableView reloadData];

}
;

-(void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    }



- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - table methods
-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _events.count;
}

-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    CalendarModel* event = _events[indexPath.row];


    NSString *dato = [[event.time objectAtIndex:0] startTime];
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ss.SSSzzz";
    NSDate *gmtDate = [formatter dateFromString: dato];
    formatter.dateFormat = @"dd-MM-yyyy HH:mm";
    dato = [formatter stringFromDate:gmtDate];

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"SportCell" forIndexPath:indexPath];
    cell.textLabel.text = [NSString stringWithFormat:@"%@",
                           event.title
                           ];
    cell.detailTextLabel.text = dato;

    return cell;
}
@end

So basically all the data i need sorted resides in the _events array. I just do not get how i sort it by date into sections. The reason why startTime and endTime are NSStrings is that, that's what i am returned by the call to the shared calendar on Google

You mean group into sections and sort by time? Is each section = 1 day? Or you just want to list all the events sorted chronologically? — Jai Govindani
– Jai Govindani, Commented Mar 27, 2013 at 11:06
Each section would be a day, where an event is present. There are days with no events, days with 1 event or days with multiple events. I'd like the section header to be a date where 1 or more events was retrieved from the calendar. That way the section header would be the date (Time.startTime) (27/3-2013), the cell.textLabel.text would be the CalendarModel.Title, and the cell.detailTextLabel.text would be Time.startTime (converted to only use the actual time of day, the event starts) — catu
– catu, Commented Mar 27, 2013 at 11:16

Jai Govindani · Accepted Answer · 2013-03-27 12:18:05Z

First group all your events - you'll have to take care of variable scoping (I'm using days and groupedEvents locally but you'll have to declare those as ivars/properties)

    NSMutableArray *days = [NSMutableArray array];
    NSMutableDictionary *groupedEvents = [NSMutableDictionary dictionary];

- (void)groupEventsIntoDays
{
    for (CalendarModel *event in _events)
    {
        NSString *dato = [[event.time objectAtIndex:0] startTime];
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ss.SSSzzz";
        NSDate *gmtDate = [formatter dateFromString: dato];

        if (![days containsObject:gmtDate])
        {
            [days addObject:gmtDate];
            [groupedEvents setObject:[NSMutableArray arrayWithObject:event] forKey:gmtDate];
        }
        else
        {
            [((NSMutableArray*)[groupedEvents objectForKey:gmtDate]) addObject:event];
        }
    }

    days = [[days sortedArrayUsingSelector:@selector(compare:)] mutableCopy];
}

Section headers:

-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    UIView *header = [[UIView alloc] initWithFrame:CGRectMake(0,0,tableView.frame.size.width, 30)];
    UILabel *headerLabel = [[UILabel alloc] initWithFrame:header.bounds];
    [header addSubview:headerLabel];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"dd-MM-yyyy HH:mm";
    NSString *dateAsString = [formatter stringFromDate:[days objectAtIndex:section]];

    [headerLabel setText:dateAsString];

    return header;
}

I only touched the first two lines in your cellForRow - you can modify the rest as needed for display/formatting:

-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    NSDate *date = [days objectAtIndex:indexPath.section];
    CalendarModel *event = [((NSMutableArray*)[groupedEvents objectForKey:date]) objectAtIndex:indexPath.row];

    NSString *dato = [[event.time objectAtIndex:0] startTime];
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ss.SSSzzz";
    NSDate *gmtDate = [formatter dateFromString: dato];
    formatter.dateFormat = @"dd-MM-yyyy HH:mm";
    dato = [formatter stringFromDate:gmtDate];

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"SportCell" forIndexPath:indexPath];
    cell.textLabel.text = [NSString stringWithFormat:@"%@",
                           event.title
                           ];
    cell.detailTextLabel.text = dato;

    return cell;
}

Made the days and groupedEvents as properties. I'm getting to errors: On the line: _days = [_days sortedArrayUsingSelector:@selector(compare:)]; It says "Incompatible pointer types assigning NSMutableArray *_strong from NSArray" And on viewForHeaderInSection method it expects a return type i guess. It says Control reaches end of non-void function
My bad. Added mutableCopy to days which should take care of the warning, and added the return for the header view.
I get null values back. Added an NSLog to print _days, and nothing is in there. Is it the line "for (CalendarModel *event in _events)" that's troubling me? I wanted to use something like "for (Object *event in _events). Array output looks like this: ( "<CalendarModel> \n [title]: Everton v Stoke\n [time]: (\n \"<Time> \\n [startTime]: 2013-03-30T18:30:00.000+01:...\n</CalendarModel>",
You said you made days a property- did you init it, either with [[NSMutableArray alloc] init] or [NSMutableArray array]?

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