Why isn't my UITableViewController being populated here?

Question

Just trying to understand my table isn't being populated when my view controller appears here. I'm using AIHTTPRequest to communicated with a REST API. The call returns an array of associative arrays (which I'm assuming I'll have to cast to an NSArray of NSDictionaries).

In the header of my TableViewController:

@interface MyTableViewController : UITableViewController <UITableViewDelegate, UITableViewDataSource> { NSArray *homepageItems; } @property (nonatomic, retain) NSArray * homepageItems;

In the implementation:

@synthesize homepageItems; .... - (void)viewDidLoad { NSURL *url = [NSURL URLWithString:URL_TO_MY_API]; ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url]; [request setDelegate:self]; [request startAsynchronous];

When the data is returned:

- (void)requestFinished:(ASIHTTPRequest *)request { // Use when fetching text data NSString *responseString = [request responseString]; id response = [responseString objectFromJSONString]; homepageItems = (NSArray *)response; }

And in the Table View method:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:CellIdentifier] autorelease]; } NSDictionary *dataItem = [homepageItems objectAtIndex:indexPath.row]; // Configure the cell... cell.textLabel.text = [dataItem objectForKey:@"message"]; return cell; }

When the view loads nothing is in the table. I suspect this is happening because when the table view method is fired homepageItems hasn't been populated by the asynchronous method. How can I achieve the data being loaded into the table view?

Thanks,

EDIT: In my requestFinished method, I've examined the homepageItems object by doing the following:

for(NSDictionary *dictionary in homepageMMDs) { NSLog(@"%@", [dictionary objectForKey:@"message"]); }

And the proper messages from my API service are being logged.

Are you sure that the data you download is directly an array, and not an array in a dictionary or something ? — Jonathan.
– Jonathan., Commented Sep 19, 2011 at 21:47

Brett · Accepted Answer · 2011-09-19 21:33:48Z

2

You need to retain the homepageItems

 self.homepageItems = (NSArray *)response;

And also reload the tableview as Joe said

answered Sep 19, 2011 at 21:33

Brett

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Joe · Accepted Answer · 2011-09-20 12:39:49Z

2

Try reloading the data!

- (void)requestFinished:(ASIHTTPRequest *)request { // Use when fetching text data NSString *responseString = [request responseString]; id response = [responseString objectFromJSONString]; //Use self. to properly retain and you do not need to cast id assignments self.homepageItems = response; //Make sure you reload the data!! [self.tableView reloadData]; }

edited Sep 20, 2011 at 12:39

answered Sep 19, 2011 at 21:23

Joe

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7 Comments

barfoon Over a year ago

Hmm, doesn't seem to be any difference

Joe Over a year ago

Well now you need to make sure homepageItems is an array, not nil and the count is greater than 0, also make sure the elements are dictionaries and have a non empty value for the key message. Start setting breakpoints and logging values.

Liam Over a year ago

Have you updated the numberOfRowsInSection to be the size of the array?

barfoon Over a year ago

I've set the number of rows, sorry I should have included that in the post. In the requestFinished method I've set a breakpoint and can see the data coming back. However in the cellforRow method, it doesnt look homepageItems is populated yet or at all.

Joe Over a year ago

@barfoon: Add a minimal example of what you logged for the homePageItems object.

|

Jonathan. · Accepted Answer · 2011-09-19 21:41:33Z

You are not retaining the downloaded data:

Instead of:

- (void)requestFinished:(ASIHTTPRequest *)request {     // Use when fetching text data.     NSString *responseString = [request responseString];     id response = [responseString objectFromJSONString]; homepageItems = (NSArray *)response; }

You need to do: (crucially using self in front of homepageItems)

- (void)requestFinished:(ASIHTTPRequest *)request {     // Use when fetching text data.     NSString *responseString = [request responseString];     id response = [responseString objectFromJSONString]; self.homepageItems = (NSArray *)response; // and others have said you need to reload the tableView [self.tableView reloadData]; }

This work, however when I scroll the table view crashes. Im guessing there is a retain issue somewhere?
'unrecognized selector sent to instance 0x12dc5e8'. Happens when I assign cell.textLabel.text
That would suggest that dataItem is not an NSDictionary. Can you post the stack trace? (when it crashes type bt in the debugger console. (after the (gdb))
Looks like it was a problem with a character in message being returned. Ill have to investigate that separately. Thanks @Jonathan.

mtnBarreto · Accepted Answer · 2015-06-19 17:14:00Z

You can use this cocoapod https://github.com/xmartlabs/XLData in order to fetch data from an API endpoint and populate a UITableView/UICollectionView.

Jamal Tyson · Accepted Answer · 2011-09-19 21:25:57Z

I suggest you to create an php page which displays your API strings,before you can parse the elements and import they to wherever you want,its much easier!Related to your code i suppose you need to parse the element,as you can se here : http://www.ibm.com/developerworks/library/x-ioschat/. Lucky.

The API call is working - the responseString is correctly appearing when it is assigned.

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