Run-Time Error for TableViewDataSource file is separated - iphone

Question

When I separated a ViewController included in TableView and TableViewDataSource files,
I got a run-time error : "..EXC_BAD_ACCESS ..".
There is whole source below.
// ViewController file
<ViewController.h>
#interface ViewController : UIViewController <UITableViewDelegate>
#property (strong, nonatomic) UITableView *tableView;
#end
<ViewController.m>
- (void)viewDidLoad
{
**DS1 *ds = [[DS1 alloc] init];**
_tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 100, 320, 200) style:UITableViewStylePlain];
_tableView.delegate = self;
**_tableView.dataSource = ds;**
[self.view addSubview:_tableView];
}
// TableViewDataSource file
<DS1.h>
#interface DS1 : NSObject <UITableViewDataSource>
#property (strong, nonatomic) NSArray *dataList;
#end
<DS1.m>
#import "DS1.h"
#implementation DS1
#synthesize dataList = _dataList;
- (id)init
{
self = [super init];
if (self) {
_dataList = [NSArray arrayWithObjects:#"apple",#"banana", #"orange", nil];
}
return self;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [_dataList count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
cell.textLabel.text = [_dataList objectAtIndex:indexPath.row];
return cell;
}
#end
If I change the code of ViewController.m from
_tableView.dataSource = ds;
to
_tableView.dataSource = self;
, then it's ok. (Of course, after DataSource methods had been appended to ViewController.m)
I cannot find any problems, help me and thanks in advance.

Answer 1

If this is ARC you have to create an instance variable or a #property for your dataSource.
You allocate your dataSource ds as a local variable. But the dataSource property of the tableView does not retain ds. So at the end of viewDidLoad ARC will release ds and it gets deallocated.
save ds as a property of your viewController. like this:
#interface ViewController : UIViewController <UITableViewDelegate>
#property (strong, nonatomic) UITableView *tableView;
#property (strong, nonatomic) DS1 *dataSource;
#end
- (void)viewDidLoad
{
[super viewDidLoad]; // <-- !!!
self.dataSource = [[DS1 alloc] init];
_tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 100, 320, 200) style:UITableViewStylePlain];
_tableView.delegate = self;
_tableView.dataSource = self.dataSource;
[self.view addSubview:_tableView];
}