Add Alphabetical Headers to UITableView with a sorted array - ios

Question

I'm sorting my array by last name alphabetically. I'd like to separate this into sections with the appropriate header above each section (A, B, C, etc.).
Here's what I've tried below:
// Here is where I refresh the data and sort it based on last name
- (void)refreshData {
[[PCMSSessionManager sharedSession] refreshPCMSDataWithCompletion:^(BOOL success, NSString *errorMessage, id resultObject) {
if (success) {
NSLog(#"yay!");
self.membersArray = [[PCMSSessionManager sharedSession] memberArr];
// Let's sort the array
self.sortedArray = [self.membersArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
NSString *first = [(PCMSMember*)a lastName];
NSString *second = [(PCMSMember*)b lastName];
return [first compare:second];
}];
[self.tableView reloadData];
} else {
NSLog(#"boooo!!!!");
}
}];
}
- (NSDictionary *)indexedMembers
{
NSMutableDictionary *indexedContacts = [NSMutableDictionary new];
for (PCMSMember *member in self.sortedArray)
{
NSString *sortString = member.lastName;
NSString *sortLetter = [sortString substringToIndex:1];
/* see if that letter already exists as an index */
BOOL foundKey = NO;
for (NSString *key in [indexedContacts allKeys])
{
if ([key isEqualToString:sortLetter])
{
foundKey = YES;
}
}
NSMutableArray *valueArray;
if (foundKey)
{
valueArray = [((NSArray *)indexedContacts[sortLetter]) mutableCopy];
}
else
{
valueArray = [NSMutableArray new];
}
[valueArray addObject:member];
indexedContacts[sortLetter] = [valueArray copy];
}
return [indexedContacts copy];
}
// Here's my table data
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [[[self indexedMembers] allKeys] count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSDictionary *indexedContacts = [self indexedMembers];
NSArray *myKeys = [indexedContacts allKeys];
NSString *key = myKeys[section];
return [((NSArray *)[self indexedMembers][key]) count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellIdentifier = #"cellIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
// Configure the cell...
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}
if (self.isPhysician == YES) {
NSString *key = [[self indexedMembers] allKeys][indexPath.section];
PCMSMember *currentMember = ((NSArray *)[self indexedMembers][key])[indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:#"%# %#", currentMember.firstName, currentMember.lastName];
}
return cell;
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [[self indexedMembers] allKeys][section];
}
UPDATE:
This is getting me closer to what I want.
The data is loading, it's being grouped properly and the headers are showing.
But it's not in alphabetical order.
How can I improve this code to show alphabetically?
It's showing in alphabetical order in my console, just not in the app.

Answer 1

The NSMutableDictionary is unordered by definition. It is not the natural choice if you rely on the order of the stored objects. I suggest you to use NSMutableArray instead. To store the tableview data for each section you can use this mini class
#interface MembersWithSameInitial : NSObject
#property (strong) NSString* initial;
#property (strong) NSMutableArray<PCMSMember*>* members;
#end
#implementation MembersWithSameInitial
#end
After you have sorted the members, all the data for the tableview can be produced with this before tableView reload.
NSMutableArray<MembersWithSameInitial*>* groupedMembers = [[NSMutableArray alloc] init];
for (PCMSMember* member in sortedArray) {
NSString* inicial = [member.lastName substringToIndex:1];
MembersWithSameInitial* last = [groupedMembers lastObject];
if (last && [last.initial isEqualToString:inicial]) {
[last.members addObject:member];
} else {
MembersWithSameInitial* newGroup = [[MembersWithSameInitial alloc] init];
newGroup.initial = inicial;
newGroup.members = [[NSMutableArray alloc] initWithObjects:member, nil];
[groupedMembers addObject:newGroup];
}
}
Since the structure of groupedMembers fits to a grouped tableView, the dataSource methods will have trivial implementations. Assuming, that you have stored groupedMembers in a property.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return self.groupedMembers.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.groupedMembers[section].members.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
//...
PCMSMember *currentMember = self.groupedMembers[indexPath.section].members[indexPath.row];
//...
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return groupedMembers[section].initial;
}

Answer 2

Suggestion:
Create two properties
#property NSMutableArray *keys; // for the letters in alphabetical order
#property NSMutableDictionary *indexedContacts; // same as your implementation.
In the method refreshData call the method to create the data source and then reload the table view on the main thread.
Actually you don't need the properties memberArray and sortedArray anymore. The sorted array is passed to the method to create the data source.
- (void)refreshData {
[[PCMSSessionManager sharedSession] refreshPCMSDataWithCompletion:^(BOOL success, NSString *errorMessage, id resultObject) {
if (success) {
NSLog(#"yay!");
self.membersArray = [[PCMSSessionManager sharedSession] memberArr];
// Let's sort the array
NSArray *sortedArray = [self.membersArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
NSString *first = [(PCMSMember*)a lastName];
NSString *second = [(PCMSMember*)b lastName];
return [first compare:second];
}];
[self indexMembers:sortedArray];
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
} else {
NSLog(#"boooo!!!!");
}
}];
}
The method indexMembers initializes the properties keys and indexedContacts and creates the data source.
- (void)indexMembers:(NSArray *)sortedMembers
{
self.keys = [[NSMutableArray alloc] init];
self.indexedContacts = [[NSMutableDictionary alloc] init];
for (PCMSMember *member in sortedMembers)
{
NSString *sortString = member.lastName;
NSString *sortLetter = [sortString substringToIndex:1];
/* see if that letter already exists as an index */
NSArray *keyArray = self.indexedContacts[sortLetter];
NSMutableArray *valueArray;
if (keyArray) {
// array for key exists, use it
valueArray = [keyArray mutableCopy];
} else {
// array for key does not exist, create a new one
valueArray = [NSMutableArray new];
// and add the letter to keys
[self.keys addObject:sortLetter];
}
[valueArray addObject:member];
self.indexedContacts[sortLetter] = [valueArray copy];
}
}
numberOfSectionsInTableView returns the number of keys
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return self.keys.count;
}
numberOfRowsInSection gets the appropriate array for the given section and returns the number of items.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSString *letter = self.keys[section];
NSArray *memberArray = self.indexedContacts[letter];
return memberArray.count;
}
In cellForRowAtIndexPath use the method dequeueReusableCellWithIdentifier: forIndexPath: to get always a valid cell. Then like in numberOfRowsInSection get the actual member array and populate the label.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellIdentifier = #"cellIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];
// Configure the cell...
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
if (self.isPhysician == YES) {
NSString *letter = self.keys[indexPath.section];
NSArray *memberArray = self.indexedContacts[letter];
PCMSMember *currentMember = memberArray[indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:#"%# %#", currentMember.firstName, currentMember.lastName];
}
return cell;
}
titleForHeaderInSection simply returns the letter for the section
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return self.keys[section];
}
You're calling indexedMembers too much. This is very expensive.
I couldn't test the code, maybe there is a self or something else missing but you get an impression of the workflow.