Question

I am trying to populate a TableView situated within a UIViewController with a collection of objects when a button is clicked.

The problem is that cellForRowAtIndexPath seems to be expecting ‘votes’ to be an instantiated object, which it isn’t until the button is pressed.

I’m not sure I’m going about this the correct way and would appreciate any assistance anybody could give me.

I have specified the delegate and datasource as follows:

@interface MyViewController : UIViewController<UITableViewDelegate, UITableViewDataSource>

I have completed my implementation of numberOfRowsInSection as follows:

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

I have completed my implementation of cellForRowAtIndexPath as follows:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    static NSString *CellIdentifier = @"Votes";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    // Configure the region cell
    CandidatePhrase *phrase = [self.votes objectAtIndex:indexPath.row];
    cell.textLabel.text = phrase.phrase;

    return cell;

}

On button press I’m loading an array with a list of objects

_votes = [[NSArray alloc] initWithObjects:myCandidatePhrase.votes, nil];

I’m just now clear on how the table will bind each time I press the button.

Here’s the error I’m currently getting, presumably because the votes array hasn’t been instantiated?

2011-12-09 22:34:48.979 MyApp[3809:fb03] -[NSObject tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x6b49b20

Answer 1

The tableView instance (not the view controller) is going to call its delegate methods as soon as it is instantiated and whenever it is informed of a change to the table view. So it doesn’t matter if votes is instantiated or not for the delegate method to be called.

However, if you want it to know that there are no rows when votes has not been instantiated, try this

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (votes != nil)
        return [self.votes count];
    else
        return 0;
}

Once you have instantiated votes, you want to call reloadData on your tableView.

Don’t forget to add your view controller as the delegate for the tableView, if it is not already.