Question

In my header file:

@interface HTMLClassesViewController : UITableViewController <UITableViewDataSource, UITableViewDelegate>

So I did declare the dataSource and delegate.

In my implementation file:

- (void)viewDidLoad {

    [super viewDidLoad];

    if (self.arrayOfClasses == nil) {
        self.arrayOfClasses = [[NSMutableArray alloc] init];
    }
    NSMutableArray *array = [[NSMutableArray alloc] init];
    ... // Gather data from HTML source and parse it into "array"
    self.arrayOfClasses = array; //arrayOfClasses here is non-nil (with correct objects)
    NSLog(@"%@ test1", [self.arrayOfClasses objectAtIndex:0]);
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    NSLog(@"%@ test1.5", [self.arrayOfClasses objectAtIndex:0]);
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
NSLog(@"%@ test2", [self.arrayOfClasses objectAtIndex:0]);
    return [self.arrayOfClasses count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSLog(@"%@ test3", [self.arrayOfClasses objectAtIndex:0]);
    static NSString *CellIdentifier = @"WebCollegeCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }
    cell.textLabel.text = [self.arrayOfClasses objectAtIndex:indexPath.row];
    return cell;
}

And this is the output from NSLog:

2012-11-24 22:52:19.125 ArizonaCollegeSearch[72404:c07] CSE 240 test1
2012-11-24 22:52:19.126 ArizonaCollegeSearch[72404:c07] CSE 240 test1.5
2012-11-24 22:52:19.127 ArizonaCollegeSearch[72404:c07] (null) test1.5
2012-11-24 22:52:19.127 ArizonaCollegeSearch[72404:c07] (null) test2

As you can see, numberOfSectionsInTableView is being called with an non-null object, and then with a null object, and numberOfRowsInSection is being called with a null object, and cellForRowAtIndexPath is not being called at all. I don’t even have a [self.tableView reloadData] anywhere.

Any suggestions?

Answer 1

So the property holding your array needs to be declared strong, else it will get deallocated when the variable it has been assigned to is deallocated. And in the case of a local variable (your NSMutableArray *array), that’s the end of its scope, e.g. when the function viewDidLoad returns.