Grouped Tableview From JSON Data - ios

Question

I've been following a tutorial on YouTube and trying to expand its functionality. I figured out how to send the retrieveData method to a background thread using GCD, figured out how to use Reachability to keep the app from crashing when in Airplane Mode, and now I'm trying to change the tableview to a grouped style. After a couple of weeks I'm at my wit's end.
What I want to do is have the UITableView grouped using the key "country" to establish the groups, and any city within that country appear in the group's cells. The number of countries in the database will change, as will the number of cities.
I'm not even sure it's possible given the data structure, but if it is, I could use some suggestions.
The JSON data is structured like this:
[{"id":"1","cityName":"London","cityState":"London","cityPopulation":"8173194","country":"United Kingdom"}
Here is the .m file:
#import "CitiesViewController.h"
#import "City.h"
#import "DetailViewController.h"
#import "Reachability.h"
#define getDataUrl #"http://www.conkave.com/iosdemos/json.php"
#interface CitiesViewController ()
#end
#implementation CitiesViewController
#synthesize jsonArray, citiesArray;
- (void)viewDidLoad {
[super viewDidLoad];
//Set the title of our VC
self.title = #"Cities of the World";
//Load data
[self retrieveData];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
return citiesArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
City * cityObject;
cityObject = [citiesArray objectAtIndex:indexPath.row];
cell.textLabel.text = cityObject.cityName;
cell.detailTextLabel.text = cityObject.cityCountry;
//Accessory
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}
#pragma mark - Navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
if ([[segue identifier] isEqualToString:#"pushDetailView"])
{
NSIndexPath * indexPath = [self.tableView indexPathForSelectedRow];
//Get the object for the selected row
City * object = [citiesArray objectAtIndex:indexPath.row];
[[segue destinationViewController] getCity:object];
}
}
#pragma mark -
#pragma mark Class Methods
- (void) retrieveData;
{
Reachability *networkReachability = [Reachability reachabilityForInternetConnection];
NetworkStatus networkStatus = [networkReachability currentReachabilityStatus];
if (networkStatus == NotReachable) {
UIAlertView *message = [[UIAlertView alloc] initWithTitle:#"No Internet"
message:#"You must have an internet connection for this feature"
delegate:self
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[message show];
[self.refreshControl endRefreshing];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
return;
}
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
//Retrieve the data asynchronously
dispatch_async(queue, ^{
NSURL * url = [NSURL URLWithString:getDataUrl];
NSData * data = [NSData dataWithContentsOfURL:url];
jsonArray = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
//Set up our cities array
citiesArray = [[NSMutableArray alloc] init];
//Loop through our jsonArray
for (int i = 0; i < jsonArray.count; i++)
{
//Create our city object
NSString * cID = [[jsonArray objectAtIndex:i] objectForKey:#"id"];
NSString * cName = [[jsonArray objectAtIndex:i] objectForKey:#"cityName"];
NSString * cState = [[jsonArray objectAtIndex:i] objectForKey:#"cityState"];
NSString * cPopulation = [[jsonArray objectAtIndex:i] objectForKey:#"cityPopulation"];
NSString * cCountry = [[jsonArray objectAtIndex:i] objectForKey:#"country"];
//Add the city object to our cities array
[citiesArray addObject:[[City alloc] initWithCityName:cName andCityState:cState andCityCountry:cCountry andcityPopulation:cPopulation andCityID:cID]];
}
//Back to main thread to update UI.use dispatch_get_main_queue() to get main thread
dispatch_sync(dispatch_get_main_queue(), ^{
//Reload our table view
[self.tableView reloadData];
});
});
}
#end

Answer 1

You can group the data yourself pretty easily in a few ways. One way is by using an array for ordering the countries and a dictionary to group the cities within them.
After you are done creating your City objects, you can do something like this:
// you probably want to save these as instance properties
NSMutableArray *countries = [NSMutableArray new];
NSMutableDictionary *citiesForCountries = [NSMutableDictionary new];
for(City *city in citiesArray)
{
NSString *currentCountry = city.country;
NSMutableArray *citiesInCountry = citiesForCountries[#"currentCountry"];
// first city for this country, so add it to our ordered list and create an array to populate with cities
if(! citiesInCountry)
{
[countries addObject:currentCountry];
citiesInCountry = [NSMutableArray new];
citiesForCountries[#"currentCountry"] = citiesInCountry;
}
[citiesInCountry addObject:city];
}
// Then here are some of the relevant methods on how you would use these data structures
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return countries.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSString *country = countries[section];
NSArray *cities = citiesForCountries[country];
return cities.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
City * cityObject;
NSString *country = countries[indexPath.section];
NSArray *cities = citiesForCountries[country];
cityObject = cities[indexPath.row];
cell.textLabel.text = cityObject.cityName;
cell.detailTextLabel.text = cityObject.cityCountry;
//Accessory
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}