为什么我的 prepareForSegue 会崩溃

Question

I am trying to pass in IndexPath through a segue though a navigationController, but it crashes on line:

view.selectedAccount = self.selectedAccountRow;

thanks

-(IBAction)changeButtonPressed:(id)sender {

CGPoint buttonPosition = [sender convertPoint:CGPointZero toView:self.accountTableView];
NSIndexPath *indexPath = [self.accountTableView indexPathForRowAtPoint:buttonPosition]
self.indexPath = indexPath;
NSLog(@"%ld",(long)indexPath.row);
}

and

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    [super prepareForSegue:segue sender:sender];
    ViewController2 *view = [segue destinationViewController];
    view.selectedAccount = self.indexPath;
}

answer here: Set NSString Object, prepareForSegue through UINavigationController

Answer 1

I see many errors:

self.selectedAccountRow never gets defined, change to this:

-(IBAction)changeButtonPressed:(id)sender {
  CGPoint buttonPosition = [sender convertPoint:CGPointZero toView:self.accountTableView];
  NSIndexPath *indexPath = [self.accountTableView indexPathForRowAtPoint:buttonPosition]
  self.selectedAccountRow = indexPath;
}

When using [segue destinationViewController] you need to ensure that the class your assingning is the right one:

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
  ViewController2 *view = (ViewController2*)[segue destinationViewController];
  view.selectedAccount = self.selectedAccountRow;
}

There's no need to declare the as strong, as it is the default one, but it's recommender as it's easier to read, and it's a good coding practice.

@property (strong, nonatomic) NSIndexPath *selectedAccount;

You need to name better your classes and properties, if you declare a viewController subclass, the name should be self explanatory, maybe you can name it detailViewController instead on viewController2 .

Also, you should consider using a 2-3 letters prefix for your classes, please read good obj-c practices in here: Objective-C Good practices

Answer 2

Right click on your view in IB and remove and instances where there is a yellow warning sign. Run and everything should work.