Obj-C, iOS, How do I sort by value and not key, sortedArrayUsingSelector, currently @selector(compare:)]

Question

I need to sort by value instead of Key, I think....

Heres where I populate my arrarys

const char *sql = "select cid, category from Categories ORDER BY category DESC";
sqlite3_stmt *statementTMP;

int error_code = sqlite3_prepare_v2(database, sql, -1, &statementTMP, NULL);
if(error_code == SQLITE_OK) {
    while(sqlite3_step(statementTMP) == SQLITE_ROW)
    {
        int cid = sqlite3_column_int(statementTMP, 0);
        NSString *category = [[NSString alloc] initWithUTF8String:(char *)sqlite3_column_text(statementTMP, 1)];

        NSArray *arr=[[NSArray alloc]initWithObjects:category,nil];

        [arrayTmp setObject:arr forKey:[NSString stringWithFormat:@"%i",cid]];
        [self.cidList addObject:[NSString stringWithFormat:@"%i",cid]];

        [category release];
        [arr release];
    }
}
sqlite3_finalize(statementTMP);
sqlite3_close(database);

self.allCategories = arrayTmp;
[arrayTmp release];

Heres the method where the arrays are re-sorted.

- (void)resetSearch {

NSMutableDictionary *allCategoriesCopy = [self.allCategories mutableDeepCopy];
self.Categories = allCategoriesCopy;
[allCategoriesCopy release];
NSMutableArray *keyArray = [[NSMutableArray alloc] init];
[keyArray addObject:UITableViewIndexSearch];
[keyArray addObjectsFromArray:[[self.allCategories allKeys] 
                               sortedArrayUsingSelector:@selector(compare:)]];
self.keys = keyArray;
[keyArray release];
}

This is a problem i've had for some time, last time I looked at this I could find an altervative to sortedArrayUsingSelector compare?

EDIT

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

NSUInteger section = [indexPath section];
NSUInteger row = [indexPath row];

NSString *key = [keys objectAtIndex:section];
NSArray *nameSection = [Categories objectForKey:key];

static NSString *SectionsTableIdentifier = @"SectionsTableIdentifier";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
                         SectionsTableIdentifier ];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault 
                                   reuseIdentifier: SectionsTableIdentifier ] autorelease];
}

cell.textLabel.text = [nameSection objectAtIndex:row];
return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 

NSUInteger section = [indexPath section];
NSUInteger row = [indexPath row];

NSString *key = [keys objectAtIndex:section];
NSArray *nameSection = [Categories objectForKey:key];

NSLog(@"the selected cid is = %i",[key intValue]); 

selectButton.enabled = YES;
}

Anyone?

Answer 1

Your obviously attempting to construct an array for use in the -[UITableviewDatasource sectionIndexTitlesForTableView:]. As such, you need an array that looks like this (pseudo-code):

[UITableViewIndexSearch, 0_sectionTitle, 1_sectionTitle, 2_sectionTitle, ...]

I think your immediate problem is that you try to add the UITableViewIndexSearch string constant to the array before you sort which makes it impossible for it end up as the first element unless all your other elements sort below U.

The fix is simple, just add the constant after the sort. You can clean the code up while you're at it:

  NSMutableArray *secIdx=[NSMutableArray arrayWithCapacity:[[self.allCategories allKeys] count]];
  [secIdx addObjectsFromArray:[self.allCategories allKeys]];
  [secIdx sortUsingSelector:@selector(compare:)];
  [secIdx insertObject:UITableViewIndexSearch atIndex:0];
  self.keys=secIdx;

Note that secIdx is autoreleased so you don't have to release it.

Aside from this problem, your code has a lot of unnecessary/dangerous elements that will make your app fragile and hard to maintain.

1. You are using a lot of init for objects that you could use autoreleased convenience methods for. The 'init`s poise the risk of memory leaks but give you no advantage.
2. You need to wrap scalar values in objects so they can be easily managed in collections.
3. You are using an unnecessary array.

You can rewrite the first block like so:

const char *sql = "select cid, category from Categories ORDER BY category DESC";
sqlite3_stmt *statementTMP;

int error_code = sqlite3_prepare_v2(database, sql, -1, &statementTMP, NULL);
if(error_code == SQLITE_OK) {
    NSNumber *cidNum; //... move variable declerations outside of loop
    NSString *category; //.. so they are not continously recreated
    [self.allCategories removeAllObjects]; //... clears the mutable dictionary instead of replacing it
    while(sqlite3_step(statementTMP) == SQLITE_ROW){
        cidNum=[NSNumber numberWithInt:(sqlite3_column_int(statementTMP, 0))]; 
        category=[NSString stringWithUTF8String:(char *)sqlite3_column_text(statementTMP, 1)];
        //... adding the autoreleased category and cidNum to array/dictionary automatically retains them
        [self.allCategories addObject:category forKey:cidNum]; 
        [self.cidList addObject:cidNum];

        //[category release]; ... no longer needed
        //[arr release]; ... no longer needed
    }
}
sqlite3_finalize(statementTMP);
sqlite3_close(database);

//self.allCategories = arrayTmp; ... no longer needed
//[arrayTmp release]; ... no longer needed

Answer 2

Use -sortedArrayUsingComparator: (or -sortedArrayUsingFunction:context: if you can't use blocks). Example:

NSDictionary *categories = [self allCategories];
NSArray *keysSortedByValue = [[categories allKeys] sortedArrayUsingComparator:
^(id left, id right) {
    id lval = [categories objectForKey:left];
    id rval = [categories objectForKey:right];
    return [lval compare:rval];
}];

Answer 3

You could make a small model class Category and implement compare inside of it, then sort an array of those objects using that compare:.

Here's some info - How to sort an NSMutableArray with custom objects in it?

Answer 4

Perhaps you're looking for NSSortDescriptor (and the corresponding sort method, -[NSArray sortedArrayUsingDescriptors]) and friends?

Answer 5

On your sorting function u should try this:

NSArray *cntxt; //im not sure this is the correct type that ur using on keyArray
[keyArray addObjectsFromArray:[self.allCategories allKeys]];
[keyArray sortUsingFunction:compareFunction context:cntxt];

And the compare function you modify to your needs

NSInteger compareFunction(id x, id y, void *context) {
    //NSArray *ctxt = context;
    NSArray *c1 = x;
    NSArray *c2 = y;

    if ([c1 value] < [c2 value])
        return NSOrderedDescending;
    else if ([c1 value] > [c2 value])
        return NSOrderedAscending;
    else 
        return NSOrderedSame;
}

Edit: After reading your comments and after relooking at your code, it seems like that your keyArray as objects of the type NSString, so you should change:

NSInteger compareFunction(id x, id y, void *context) {
    //NSString *ctxt = context;
    NSString *c1 = x;
    NSString *c2 = y;
    NSComparisonResult result;
    result = [c1 compare:c2];

    if (result<0)
        return NSOrderedAscending;
    else if (result>0)
        return NSOrderedDescending;
    else 
        return NSOrderedSame;
}

Answer 6

If I understood correctly then what you wish to do to get categories from database & display it on a tableView with alphabetical sorting, index on right & search bar on top. Ideally, you would like to display the Contacts application kind of a view. If that's correct, use below code for fetching items from DB & rebuilding (or resetting) it -

const char *sql = "select cid, category from Categories ORDER BY category DESC";
sqlite3_stmt *statementTMP;

NSMutableArray *arrayTmp = [[NSMutableArray alloc] init];

int error_code = sqlite3_prepare_v2(database, sql, -1, &statementTMP, NULL);
if(error_code == SQLITE_OK) {
    while(sqlite3_step(statementTMP) == SQLITE_ROW) {
         int cid = sqlite3_column_int(statementTMP, 0);
         NSString *category = [[NSString alloc] initWithUTF8String:(char *)sqlite3_column_text(statementTMP, 1)];

         NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
         [dict setObject:category forKey:@"Category"];
         [dict setObject:[NSNumber numberWithInt:cid] forKey:@"CID"];

         [arrayTmp addObject:dict];
         [dict release];
         [category release];
    }
}

sqlite3_finalize(statementTMP);
sqlite3_close(database);

self.allCategories = arrayTmp;
[arrayTmp release];

And then rebuild the items using this function -

- (void)rebuildItems {
    NSMutableDictionary *map = [NSMutableDictionary dictionary];

    for (int i = 0; i < allCategories.count; i++) {
        NSString *name = [[allCategories objectAtIndex:i] objectForKey:@"Category"];
        NSString *letter = [name substringToIndex:1];
        letter = [letter uppercaseString];

        if (isdigit([letter characterAtIndex:0]))
              letter = @"#";

        NSMutableArray *section = [map objectForKey:letter];
        if (!section) {
            section = [NSMutableArray array];
            [map setObject:section forKey:letter];
        }
        [section addObject:[allCategories objectAtIndex:i]];
    }

    [_items release];
    _items = [[NSMutableArray alloc] init];
    [_sections release];
    _sections = [[NSMutableArray alloc] init];

    NSArray* letters = [map.allKeys sortedArrayUsingSelector:@selector(caseInsensitiveCompare:)];
    for (NSString* letter in letters) {
        NSArray* items = [map objectForKey:letter];
        [_sections addObject:letter];
        [_items addObject:items];
    }
}

Now, displaying items in tableView, use below methods -

#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)aTableView {
    if (_sections.count)
        return _sections.count;
    else
        return 1;
}

- (NSInteger)tableView:(UITableView*)tableView sectionForSectionIndexTitle:(NSString *)title
               atIndex:(NSInteger)index {

    if (tableView.tableHeaderView) {
        if (index == 0) {
            [tableView scrollRectToVisible:tableView.tableHeaderView.bounds animated:NO];
            return -1;
        }
    }

    NSString* letter = [title substringToIndex:1];
    NSInteger sectionCount = [tableView numberOfSections];
    for (NSInteger i = 0; i < sectionCount; i++) {
         NSString* section = [tableView.dataSource tableView:tableView titleForHeaderInSection:i];
         if ([section hasPrefix:letter]) {
             return i;
         }
    }

    if (index >= sectionCount) {
        return sectionCount-1;
    } else {
        return index;
    }
}


- (NSArray*)lettersForSectionsWithSearch:(BOOL)withSearch withCount:(BOOL)withCount {
    if (isSearching)
        return nil;

    if (_sections.count) {
        NSMutableArray* titles = [NSMutableArray array];
        if (withSearch) {
            [titles addObject:UITableViewIndexSearch];
        }
        for (NSString* label in _sections) {
            if (label.length) {
                NSString* letter = [label substringToIndex:1];
                [titles addObject:letter];
            }
        }
        if (withCount) {
            [titles addObject:@"#"];
        }
        return titles;
    } else {
        return nil;
    }
}


- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
    return [self lettersForSectionsWithSearch:YES withCount:NO];
}


- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section {
    if (_sections.count) {
        NSArray* items = [_items objectAtIndex:section];
        return items.count;
    } else {
        return _items.count;
    }
}


- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    if (_sections.count) 
        return [_sections objectAtIndex:section];

    return nil;
}


- (id)tableView:(UITableView *)tableView objectForRowAtIndexPath:(NSIndexPath *)indexPath {
    if (_sections.count) {
        NSArray *section = [_items objectAtIndex:indexPath.section];
        return [section objectAtIndex:indexPath.row];
    } else {
        return [_items objectAtIndex:indexPath.row];
    }
}


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

    // Create your UITableViewCell.

    // Configure the cell.
    NSDictionary *dict = [self tableView:tableView objectForRowAtIndexPath:indexPath];
    cell.textLabel.text = [dict objectForKey:@"Category"];
            cell.detailTextLabel.text = [NSString stringWithFormat:%d, [[dict objectForKey:@"CID"] intValue]];
    return cell;
}

#pragma mark -
#pragma mark Table view delegate


- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    if (isSearching)
        return nil;

    NSString *title = @"";
    if (_sections.count) {      
        title = [[_sections objectAtIndex:section] substringToIndex:1];
    } else {
        return nil;
    }

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 20)];
    view.backgroundColor = [UIColor colorWithRed:(58/255.0) green:(27/255.0) blue:(6/255.0) alpha:1.0];

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 1, 50, 18)];
    label.textColor = [UIColor whiteColor];
    label.backgroundColor = [UIColor clearColor];
    label.font = [UIFont boldSystemFontOfSize:17.0];
    label.text = title;

    [view addSubview:label];
    [label release];

    return [view autorelease];
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    NSDictionary *dict = [self tableView:tableView objectForRowAtIndexPath:indexPath];

    NSLog(@"selected row id:%d, name:%@", [dict objectForKey:@"Category"], [[dict objectForKey:@"CID"] intValue]);
}

The rest part is implementing the UISearchBarDelegate and implementing searching of tableView which can be done using below code:

- (void)searchBar:(UISearchBar *)searchbar textDidChange:(NSString *)searchText {

    [_sections removeAllObjects];
    [_items removeAllObjects];

    if([searchText isEqualToString:@""] || searchText == nil) {
        [self rebuildItems];
        return;
    }

    NSInteger counter = 0;
    for(NSDictionary *dict in allCategories) {
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        NSRange r = [[dict objectForKey:@"Category"] rangeOfString:searchText options:NSCaseInsensitiveSearch];
        if(r.location != NSNotFound) {
            if(r.location == 0) {
                [_items addObject:dict];
            }
        }
        counter++;
        [pool release];
    }

    [contactList reloadData];
}

Hope this is what you're looking for.