tableView.datasource =自身错误：无法识别的选择器

Question

When I describe tableView.datasource = self ,
the app abend with signal SIGABRT(unrecognized selector sent to instance) .

When I erase tableView.datasource = self ,
the app run but datasource method( cellForRowInSection etc) is not be reflected.

To manage the tableView , I use a UIViewController subclass.
The view is composed of multiple subviews, only one of which is a tableView .

ViewController.h

@interface ViewController : UIViewController<UITableViewDataSource,UITableViewDelegate>

ViewController.m

    @interface ViewController ()
    @property (retain, nonatomic) UITableView *tableView;
    @end
    @implementation ViewController{
      @private NSArray *_data1;
    @synthesize tableView = _tableView;

    - (void)viewDidLoad
    {
      _tableView = [[UITableView alloc]initWithFrame:CGRectMake(-10, 70, 320, 480)];
      _tableView.dataSource = self;
      _tableView.delegate = self;
      [self.view addSubview:_tableView];
    }

    - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
    {
      return [_data1 count];
    }

    - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
    {
      return [_data1[section] count];
    }

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    {
      static NSString *CellIdentifier = @"Cell";
      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
      if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
      }
      NSString *data;
      data = _data1[indexPath.section][indexPath.row];
      cell.textLabel.text = data;
      return cell;
    }

ERROR MESSAGE---------

when -tableView:numberOfRowsInSection return 1;

Assertion failure in -[UITableView dequeueReusableCellWithIdentifier:forIndexPath:], /SourceCache/UIKit_Sim/UIKit-2903.23/UITableView.m:5261

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard’

when -tableView:numberOfRowsInSection return [_data1[section]count]

[__NSCFConstantString count]: unrecognized selector sent to instance 0x100006930
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString count]: unrecognized selector sent to instance 0x100006930'

Thank you.

Answer 1

Seeing this sample code, I think that the error can be that _data1[section] is not an object that is able to use the selector count .

When you remove the ligne _tableView.dataSource = self; the method tableView:numberOfRowsInSection: is not called and your app does not crash.

Answer 2

When you set your view controller as the datasource for the table view, your view controller must then conform to the UITableViewDataSource protocol.

There are 2 required methods in that protocol:

– tableView:cellForRowAtIndexPath: required method – tableView:numberOfRowsInSection: required method

There are also a number of optional methods, including

– numberOfSectionsInTableView: – sectionIndexTitlesForTableView: – tableView:sectionForSectionIndexTitle:atIndex: – tableView:titleForHeaderInSection: – tableView:titleForFooterInSection:

If you don't at least implement the 2 required methods, your program will crash.

As the others have requested, you need to copy and paste the exact error message you are getting. That will help us understand what's going wrong.