Indexed Table View for Facebook Friends - ios

Question

I am trying to sort my Facebook friends list in order to implement an indexed table view, exactly like the one found in Facebook Messenger.
I originally tried to use the UILocalizedIndexedCollation but I am stuck on the "collationStringSelector" because my dataSource array are id<"FBGraphUser"> objects and therefore have no properties I can use for the selector. Any ideas of how to implement this (it does not have to be using this method, I am open to anything!)?
-(NSArray *)partitionObjects:(NSArray *)array collationStringSelector:(SEL)selector {
UILocalizedIndexedCollation *collation = [UILocalizedIndexedCollation currentCollation];
NSInteger sectionCount = [[collation sectionTitles] count]; // section count is take from sectionTitles and not sectionIndexTitles
NSMutableArray *unsortedSections = [NSMutableArray arrayWithCapacity:sectionCount];
// create an array to hold the data for each section
for (int i = 0; i < sectionCount; i++) {
[unsortedSections addObject:[NSMutableArray array]];
}
// put each object into a section
for (id object in array) {
NSInteger index = [collation sectionForObject:object collationStringSelector:selector];
[[unsortedSections objectAtIndex:index] addObject:object];
}
NSMutableArray *sections = [NSMutableArray arrayWithCapacity:sectionCount];
// sort each section
for (NSMutableArray *section in unsortedSections) {
[sections addObject:[collation sortedArrayFromArray:section collationStringSelector:selector]];
}
return sections;
}

Answer 1

Here is a subclass of UITableViewController that I created some time ago to make an indexed table view. I use this as a base class for the controller whose table view appears on screen, so it's intended to be a reusable class that does the hard work of creating the table. You might be able to use it as is, but I didn't try to make it too universal. I pass in a simple array of custom objects (my objects just had first and last names), and this class creates the sections and the index. So here's the code,
the .h
#interface RDIndexedTableController : UITableViewController
#property (strong,nonatomic) NSArray *inputArray;
#property (strong,nonatomic) NSString *sectionKey;
#property (strong,nonatomic) NSString *secondarySortKey;
#property (nonatomic, retain) NSMutableArray *sectionsArray;
#property (nonatomic, retain) UILocalizedIndexedCollation *collation;
-(void)convertArray:(NSArray *)input usingSectionKey:(NSString *)key secondarySortKey:(NSString *)sorter;
#end
The .m
#interface RDIndexedTableController ()
#property (strong,nonatomic) NSMutableArray *firstLetterArray;
#end
#implementation RDIndexedTableController
-(void)convertArray:(NSArray *)input usingSectionKey:(NSString *)key secondarySortKey:(NSString *)sorter {
self.inputArray = input;
self.sectionKey = key;
self.secondarySortKey = sorter;
[self configureSections];
}
- (void)configureSections {
self.collation = [UILocalizedIndexedCollation currentCollation];
NSInteger sectionTitlesCount = [[self.collation sectionTitles] count];
NSMutableArray *newSectionsArray = [[NSMutableArray alloc] initWithCapacity:sectionTitlesCount];
for (int index = 0; index < sectionTitlesCount; index++) {
NSMutableArray *array = [[NSMutableArray alloc] init];
[newSectionsArray addObject:array];
}
for (id obj in self.inputArray) {
NSInteger sectionNumber = [self.collation.sectionTitles indexOfObject:[[obj valueForKey:self.sectionKey] substringToIndex:1]];
NSMutableArray *sectionForObjects = [newSectionsArray objectAtIndex:sectionNumber];
[sectionForObjects addObject:obj];
}
for (int index = 0; index < sectionTitlesCount; index++) {
NSMutableArray *objectArrayForSection = [newSectionsArray objectAtIndex:index];
NSArray *firstSortedObjectArrayForSection = [self.collation sortedArrayFromArray:objectArrayForSection collationStringSelector:NSSelectorFromString(self.secondarySortKey)];
NSArray *sortedObjectArrayForSection = [self.collation sortedArrayFromArray:firstSortedObjectArrayForSection collationStringSelector:NSSelectorFromString(self.sectionKey)];
[newSectionsArray replaceObjectAtIndex:index withObject:sortedObjectArrayForSection];
}
self.sectionsArray = newSectionsArray;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return self.collation.sectionTitles.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
NSArray *objectsInSection = [self.sectionsArray objectAtIndex:section];
return objectsInSection.count;
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return self.collation.sectionTitles[section];
}
-(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
if ([[self.sectionsArray objectAtIndex:section] count] == 0) {
return 0;
}else{
return 30;
}
}
- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
return #[#"A",#"B",#"C",#"D",#"E",#"F",#"G",#"H",#"I",#"J",#"K",#"L",#"M",#"N",#"O",#"P",#"Q",#"R",#"S",#"T",#"U",#"V",#"W",#"X",#"Y",#"Z"];
}
- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index {
return [self.collation sectionForSectionIndexTitleAtIndex:index];
}
In the table view controller that appears in the app, I only need this small amount of code to populate the table,
-(void)viewDidLoad {
[super viewDidLoad];
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"Cell"];
NSMutableArray *mut = [NSMutableArray new];
// create the Person objects and add them to the array here
[self convertArray:mut usingSectionKey:#"lastName" secondarySortKey:#"firstName"];
[self.tableView reloadData];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
NSString *first = [self.sectionsArray[indexPath.section][indexPath.row] valueForKey:#"firstName"];
NSString *last = [self.sectionsArray[indexPath.section][indexPath.row] valueForKey:#"lastName"];
cell.textLabel.text = [NSString stringWithFormat:#"%# %#",first,last];
return cell;
}