无法在UITableView实现中调用委托/数据源方法

Question

I have created .h and .m files for UITableView called mainTableViewgm.h and mainTableViewgm.m resp. and I am calling - initWithFrame : method from my main view controller to this mainTableViewgm.m implementation file

[[mainTableViewgm alloc]initWithFrame:tableViewOne.frame]

Note that this tableview is in my main view controller. But I have created separate files for the tableView and have also set the custom class to mainTableViewgm in storyboard.

the -initWithFrame: methods appears as follows

- (id)initWithFrame:(CGRect)frame
{

//NSLog(@"kource data");
self = [super initWithFrame:frame];
if (self)
{
    [self setDelegate:self];
    [self setDataSource:self];
    [self tableView:self cellForRowAtIndexPath:0];
    [self tableView:self numberOfRowsInSection:1];
    // Initialization code
}

return self;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSLog(@"kource data");
return 1;
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath     *)indexPath
{
NSLog(@"kource data2");
UITableViewCell*cellOne =[[UITableViewCell alloc]init];
cellOne.detailTextLabel.text=@"text did appear";
return cellOne;
}

the -initWithFrame: is being called fine along with the 'if (self)' block in this method. But the problem is numberOfRowsInSection: and cellForRowAtIndexPath: are not being automatically called here . kource data / kource data2 never appear in log. What do I do to load the table? Are the delegate / datasource being set incorrectly?

I must mention that I have also set the UITableViewDelegate and UITableviewDataSource protocols:

@interface mainTableViewgm : UITableView <UITableViewDelegate,UITableViewDataSource>
@end

Help will be much appreciated. Thank you.

Answer 1

Your tableview is not loaded when the controller is initializing, so you cannot do that in the init methods. You have to move your code to the viewDidLoad method.

Also you are not setting the delegate and datasource on the tableview object (probably a type, you are setting them on the view controller). It should look like this:

- (void)viewDidLoad:(BOOL)animated {
    [super viewDidLoad:animated];
    [self.tableView setDelegate:self];
    [self.tableView setDataSource:self]; // <- This will trigger the tableview to (re)load it's data
}

Next thing is to implement the UITableViewDataSource methods correctly. UITableViewCell *cellOne =[[UITableViewCell alloc] init]; is not returning a valid cell object. You should use at least initWithStyle: . And take a look how to use dequeueReusableCellWithIdentifier:forIndexPath: . A typical implementation would look like this:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";

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

    // Update cell contents
    cell.textLabel.text = @"Your text here";
    cell.detailTextLabel.text=@"text did appear";

    return cell;
}

Answer 2

I can't believe I've been doing XCode programming for two years, and still hit this issue.

I had the same problem with XCode 6.1 - I was setting my UITableView 's delegate & dataSource in the viewWillAppear function, but none of the delegate functions were kicking in.

However, if I right-clicked on the UITableView on the Storyboard, the circles for delegate and dataSource were empty.

The solution, then, is to hold down the CTRL key, and drag from each of these circles up to the name of your UIView which contains your UITableView :

After doing this, my UITableView happily populated itself.

(So, we're upto v6.1 of XCode now are we ? Do you think Apple ever going to make this thing, you know, friendly ...? I would quite like to add a Bookmark in my code... that'd be a nice feature.)