How should I ideally create a well-structured UITableViewDataSource? - ios

Question

I have an NSArray of songs fetched from a server. That is my raw data source. The array contains custom objects which have an NSDictionary and NSArray as backend.
I am wondering if implementing a formatted data source using an NSDictionary will be wise. The dictionary will have section headers as keys, and the value of a certain key will have an NSArray containing the rows for that section.
I will be iterating through my raw data source and arranging it alphabetically into the dictionary.
I have a feeling that this is not a solid implementation and is very expensive. Is there any other, more solid implementation than this?

Answer 1

For small tables, rather than NSDictionary, I generally use NSArray, since dictionaries don't preserve order (and you probably don't want to continually re-sort). So I usually have an array of sections, for which I have for each section entry, at the very least, a section title and an array of rows. My array of rows has, that information that I need to present a given row (e.g. the text of the row, etc.).
The individual row and section objects, you can implement those as a NSDictionary objects themselves (and sometimes when parsing the data from JSON or XML, that's easiest), but I generally define my own Row and Section objects, e.g.:
#interface Row : NSObject
#property (nonatomic, strong) NSString *title;
#property (nonatomic, strong) NSString *subtitle;
#end
and
#interface Section : NSObject
#property (nonatomic, strong) NSString *title;
#property (nonatomic, strong) NSMutableArray *rows;
#end
Then my table view controller has an NSArray for the sections:
#property (nonatomic, strong) NSMutableArray *sections;
And I populate it like so:
self.sections = [NSMutableArray array];
Section *sectionObject;
sectionObject = [[Section alloc] initWithTitle:#"Marx Brothers" rows:nil];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Chico" subtitle:#"Leonard Marx"]];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Harpo" subtitle:#"Adolph Marx"]];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Groucho" subtitle:#"Julius Henry Marx"]];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Zeppo" subtitle:#"Herbert Manfred Marx"]];
[self.sections addObject:sectionObject];
sectionObject = [[Section alloc] initWithTitle:#"Three Stooges" rows:nil];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Moe" subtitle:#"Moses Harry Horwitz"]];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Larry" subtitle:#"Louis Feinberg"]];
[sectionObject.rows addObject:[[Row alloc] initWithTitle:#"Curly" subtitle:#"Jerome Lester \"Jerry\" Horwitz"]];
[self.sections addObject:sectionObject];
And then I have the typical UITableViewDataSource methods:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [self.sections count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
Section *sectionObject = self.sections[section];
return [sectionObject.rows count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
Section *sectionObject = self.sections[section];
return sectionObject.title;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
Section *sectionObject = self.sections[indexPath.section];
Row *rowObject = sectionObject.rows[indexPath.row];
cell.textLabel.text = rowObject.title;
cell.detailTextLabel.text = rowObject.subtitle;
return cell;
}
For bigger, database data driven tables, I might not keep the data in arrays, but rather use Core Data or SQLite, but the idea is the same. Make sure I have Section and Row classes that keep my table view controller code self-explanatory and insulated from the details of the data implementation.

Answer 2

Have you tried RestKit? All you need is to provide source of json encoded objects and create model classes

Answer 3

You can use a model class and then create objects of this model class with the data from the server. Then use the array of model class objects as a source to your UITableView. You could also consider core-data , in which its very easy to create data models and relations. However it comes with a lot of additional features which might be extra baggage for you.