Dynamic arrays as section headers - iphone

Question

I have a main array, that contains a whole bunch of dictionaries, what I want to do is to have all those dictionaries sorted according to their assigned tag. This is how a dictionary might look:
date = "2012-12-04 20:26:04 +0000";
name = H;
tag = "#J";
Heres how the main array looks:
MAIN_ARRAY
- dict1
- dict2
- dict3
I want to sort the main array like this:
MAIN_ARRAY
- tag1
- dict1
- dict2
- tag2
- dict3
Heres my code:
-(NSArray *)returnTagContent {
NSArray *tags = [all valueForKey:#"tag"];
NSMutableArray *adoptTags = [[[NSMutableArray alloc] init] autorelease];
for (NSString *tagQuery in tags) {
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"tag CONTAINS[cd] %#", tagQuery];
NSArray *roughArray = [all filteredArrayUsingPredicate:predicate];
NSArray *tagContent = [[NSSet setWithArray:roughArray] allObjects];
[adoptTags addObject:tagContent];
}
return adoptTags;
}
It returns the array, but now I want to organize it into section headers. How should I go about this?
I also have another piece of code with problem for returning the section header titles:
-(NSString *)returnTitleForTags {
NSString *uniqueTag = nil;
for (NSArray *tagContent in allTags) {
uniqueTag = [[[tagContent valueForKey:#"tag"] allObjects] lastObject];
}
return uniqueTag;
}
Problem? Well, I know it's because of lastObject but any other ideas to retrieve a NSString object of the array.
UPDATE: New code changes.
I update the array to display the sections when clicked by a button so like this:
isTagFilterOn=YES;
[self loadSectionsArray];
[self.tableView reloadData];
Heres the code for cellForRowAtIndexPath:
if (isTagFilterOn==YES) {
NSDictionary *dict = [[sectionsArray objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];
cell.textLabel.text = [dict valueForKey:#"name"];
cell.detailTextLabel.text = [dict valueForKey:#"date"];
}
else {
NSString *object = all[indexPath.row];
cell.textLabel.text = [object valueForKey:#"name"];
cell.detailTextLabel.text = [object valueForKey:#"tag"];
}
The rest
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
if (isTagFilterOn==YES) {
return [sectionsArray count];
}
else {
return 1;
}
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if (isTagFilterOn==YES) {
return [[sectionsArray objectAtIndex:section] count];
}
return all.count;
}
-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
if (isTagFilterOn==YES) {
NSDictionary *dict = [[sectionsArray objectAtIndex:section] objectAtIndex:0];
return [dict objectForKey:#"tag"];
}
return nil;
}

Answer 1

I think your task becomes easier if you remove duplicate "tags" before you create the array for the table view data source:
// All tags:
NSArray *tags = [mainArray valueForKey:#"tag"];
// Remove duplicates and sort:
tags = [[[NSSet setWithArray:tags] allObjects] sortedArrayUsingSelector:#selector(compare:)];
// Build an "array of arrays (of dictionaries)" as data source:
sectionsArray = [NSMutableArray array];
for (NSString *tag in tags) {
NSPredicate *pred = [NSPredicate predicateWithFormat:#"tag == %#", tag];
NSArray *onesection = [mainArray filteredArrayUsingPredicate:pred];
[sectionsArray addObject:onesection];
}
For example, if the mainArray is
(
{ date = "2012-12-04 20:26:04 +0000"; name = H; tag = "#J"; },
{ date = "2013-12-04 20:26:04 +0000"; name = X; tag = "#J"; },
{ date = "2014-12-04 20:26:04 +0000"; name = Z; tag = "#L"; }
)
then sectionsArray will be
(
(
{ date = "2012-12-04 20:26:04 +0000"; name = H; tag = "#J"; },
{ date = "2013-12-04 20:26:04 +0000"; name = X; tag = "#J"; }
),
(
{ date = "2014-12-04 20:26:04 +0000"; name = Z; tag = "#L"; }
)
)
and you can easily access each section and each row within a section:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [sectionsArray count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [[sectionsArray objectAtIndex:section] count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = ...;
}
NSDictionary *dict = [[sectionsArray objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];
cell.textLabel.text = [dict objectForKey:#"name"];
cell.detailTextLabel.text = [dict objectForKey:#"date"];
return cell;
}
-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
NSDictionary *dict = [[sectionsArray objectAtIndex:section] objectAtIndex:0];
return [dict objectForKey:#"tag"];
}