Calling an API with UISearchBar

Question

I have a UITableView that displays results from an API. The API is called whenever the user types into the UISearchBar via searchBar:textDidChange:. Effectively implementing an autocomplete search. My problem is the results loaded into the UITableView seem to be an iteration behind the last API call.

Example: User types "union" into the UISearchBar, however no results are shown in the UITableView. User types any character after "union", "unions" for example, and the API results from "union" are displayed in the UITableView. When user scrolls down through results (of "unions", but really "union") "repopulated cells" display "unions" result.

SearchViewController.h

#import <UIKit/UIKit.h>

@interface SearchViewController : UIViewController <UITextFieldDelegate, UISearchBarDelegate, UITableViewDelegate, UITableViewDataSource, UISearchDisplayDelegate>{
    UITableView *searchTableView;
    UISearchBar *sBar;
    UISearchDisplayController *searchDisplayController;
}

@property (strong, nonatomic) NSArray *loadedSearches;

@end

SearchViewController.m

#import "SearchViewController.h"
#import "AFJSONRequestOperation.h"

@interface SearchViewController ()

@end

@implementation SearchViewController


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.title = @"Search";
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    searchTableView = [[UITableView alloc] initWithFrame:self.view.bounds];
    searchTableView.delegate = self;
    searchTableView.dataSource = self;
    [self.view addSubview:searchTableView];

    sBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, 160, 44)];
    sBar.placeholder = @"Bus Route to...";
    sBar.delegate = self;
    searchDisplayController = [[UISearchDisplayController alloc] initWithSearchBar:sBar contentsController:self];

    searchDisplayController.delegate = self;
    searchDisplayController.searchResultsDataSource = searchTableView.dataSource;
    searchDisplayController.searchResultsDelegate = searchTableView.delegate;

    searchTableView.tableHeaderView = sBar;
}

-(void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    NSString *searchQuery = [NSString stringWithFormat:@"https://api.foursquare.com/v2/venues/search?ll=40.4263,-86.9177&client_id=xxx&client_secret=yyy&v=20121223&query='%@'",searchText];

    searchQuery = [searchQuery stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    NSURL *url = [[NSURL alloc] initWithString:searchQuery];

    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];

    AFJSONRequestOperation *operation = [AFJSONRequestOperation
                                         JSONRequestOperationWithRequest:request
                                         success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON){
                                             self.loadedSearches = JSON[@"response"][@"venues"];
                                         } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON){
                                             NSLog(@"%@", error.localizedDescription);
                                         }];

    [operation start];
    [searchTableView reloadData];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return self.loadedSearches.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"];

    if(cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
    }

    cell.textLabel.text = self.loadedSearches[indexPath.row][@"name"];

    return cell;
}

@end

If my problem isn't clear, let me know.

Feel free to critique other aspects of the code, however I really would appreciate the solution to my problem:) Thanks in advance.

Example API response - http://pastebin.com/UZ1H2Zwy

Answer 1

The problem seems to be that you are refreshing the table before you get the data as you are making an asynchronous operation with AFJSONRequestOperation. So your model is probably getting updated correctly but your tableview is one refresh behind. Try moving [searchTableView reloadData] inside the block success callback:

AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request
      success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON)
      {
          self.loadedSearches = JSON[@"response"][@"venues"];

          // refreshing the TableView when the block gets the response
          [searchTableView reloadData];
      }
      failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON)
      {
          NSLog(@"%@", error.localizedDescription);
      }];

Hope this works.

Answer 2

Your requests work asynchronously, it is not probably related with scroll or something. Just result returns at that time. Try to cancel the previous requests. For example if you try to search "unions" then cancel the "union" request. Hope it helps.