Sorting custom objects in UITableView section - ios

Question

I'm making an app whereas I have created a custom class which inherits from NSObject. This class contains various properties whereas one of them is a NSDate property and another one is a NSString. I would like to sort these objects in a UITableView using sections whereas each section represents the month and year of the NSDate in the object. So far, I've only managed to populate the list using a detail UITableViewCell to show the information but I'm not sure how to go about using sections as they're dynamic and not static cells.
I kind of brainstormed solutions and one of them would be to create a for-loop for all the objects and count the number of months and return that number in the numberOfSectionsInTableView: method - but I'm far from certain if this is the best and most proper way of addressing it.
Could someone help me with this?
My custom objects contain various properties but these are the ones we need to focus on:
#property (nonatomic, strong) NSString *information;
#property (nonatomic, strong) NSDate *dateAdded;
Thank you!
Erik

Answer 1

So give your objects a yearAndMonth property. in the getter for the property, check the instance variable. If it's !0, return it. If it ==0, use NSCalendar to calculate the year and month, turn it into a number (year*100+month), save it in the ivar, and return it.
(Also make the setter on the date property zero out the yearAndMonth property.)
Now you can write code that breaks your table view into sections based on the value of this property. For any given object, it will only be calculated once, so it shouldn't impact performance over-much.

Answer 2

I think a lot of it is a matter of preference. In the past for something like this I would just create a two demential array. Where the array in the array would represent the section and when you need need a section header you pull that section array out and populate the header based on the first object in that array.
NSArray *sectionArray = [self arrayAfterSorting:customObjectArray];
//section would be something like this
NSArray *section = sectionArray[section];
return section.count;
//header
NSArray *section = sectionArray[section];
CustomObject *customObject = section[0];
return customObject.whateverHeaderShouldBeBasedOnObject;
I personally try to avoid having two separate arrays and prefer to have everything built into one two dimensional array. Hope that makes sense and helps.
Edit:
If the issue is figuring out how to sort I would look at this question and answer. Although they are talking about putting it into a dictionary I am sure you can apply the same logic to an array.
Sort NSArray with NSDate object into NSDictionary by month
Hope that helps.

Answer 3

is your Array which contains your custom Objects sorted? Probably not i guess. I'd first start with that:
NSArray *sortedObjectArray = [youArray sortedArrayUsingComparator:^NSComparisonResult(YourObjectClass *a, YourObjectClass *b) {
return [a.dateAdded compare:b.dateAdded];}];
As you now got that, it would be the best to actually find out how many table view sections you need. To loop through your sortedArray would be the best approach there. But keep in mind to do it e.g. in viewDidLoad or some place else, where you retrieve your data, to make sure that you actually perform your search and data aggregation only once.
Doing that in numberOfSectionsInTableView would cause your app to repeat all this unnecessary calculation each time the tableView is reloaded.
So, what about the sections right? I'd recommend an NSMutableArray which represent the sections you need. This object then should contain NSMutableArrays itself, which contain your custom Objects.
But first we need to find out how many section you will actually need.Just do a for loop like this:
NSMutableArray *dateArray = [[NSMutableArray alloc] init];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDate *recentDate;
for (YourObjectClass *object in sortedObjectArray) {
if (!recentDate) {
[dateArray addObject:object.dateAdded];
recentDate = object.dateAdded;
}
else {
NSDateComponents *currentDateComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:object.dateAdded];
NSDateComponents *recentDateComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:recentDate];
if (recentDateComponents.year != currentDateComponents.year || recentDateComponents.month != currentDateComponents.month) {
[dateArray addObject:object.dateAdded];
recentDate = object.dateAdded;
}
}
}
So now you got your dateArray which contains all distinct dates in terms of month and year.
NSMutableArray *finalArray = [[NSMutableArray alloc] init];
for (NSDate *date in dateArray) {
NSMutableArray *subArray = [[NSMutableArray alloc] init];
for (YourObjectClass *object in sortedObjectArray) {
NSDateComponents *currentDateComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:object.dateAdded];
NSDateComponents *recentDateComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
if (recentDateComponents.year == currentDateComponents.year || recentDateComponents.month == currentDateComponents.month) {
[subArray addObject:object];
}
else {
break;
}
}
[finalArray addObject:subArray];
}
This should be it. Now just tell your tableView Datasource that you have finalArray.count sections. And in numberOfRowsInSection: you just get the subArray on the sectionIndex and return its count value. Hope this helps you out :)
(Didn't test the code, so be aware :))

Answer 4

I managed to put this code together that works, although I realised I might want to change the UI as the data wasn't presented as well as I initially thought. This is the code I made, all the other answers helped me with this!
// Create a sections NSMutableArray
_sectionsArray = [[NSMutableArray alloc] init];
// Cycle through the workdays and populate sectionsArray
NSString *currentMonth;
NSMutableArray *currentMonthArray = [[NSMutableArray alloc] init];
for (DayModel *currentModel in sortedWorkDays)
{
// Create a currentMonthArray and initialize it
// Initial currentMonth value
if (currentMonth == nil)
{
currentMonth = [self monthFromDate:currentModel.registerDate];
}
if ([currentMonth isEqualToString:[self monthFromDate:currentModel.registerDate]])
{
NSLog(#"current");
// Current month
[currentMonthArray addObject:currentModel];
if (([sortedWorkDays indexOfObject:currentModel] + 1) == [sortedWorkDays count])
{
// Complete
NSLog(#"LAST OF ALL");
[_sectionsArray addObject:currentMonthArray];
currentMonthArray = nil;
currentMonthArray = [[NSMutableArray alloc] init];
currentMonth = [self monthFromDate:currentModel.registerDate];
[currentMonthArray addObject:currentModel];
}
} else
{
// Finished with this month
NSLog(#"LAST");
[_sectionsArray addObject:currentMonthArray];
currentMonthArray = nil;
currentMonthArray = [[NSMutableArray alloc] init];
currentMonth = [self monthFromDate:currentModel.registerDate];
[currentMonthArray addObject:currentModel];
}
}