R – class variable accessible at end of one function, and crashes on access at beginning of next

iphonensstringuitableview

(programming in iPhone objective-C)

I have a class level NSString* that I create, add property(nonatomic,retain) and synthesize code for and I can modify the string endlessly with stringByAppendingString functions and display the string using NSLog just fine. All of this is done in a subclass, overridden viewDidLoad function. When I try to access the same variable from the cellForRowAtIndexPath function when determining what to display in the cell of a tableView, the program crashes. Anyone have any clues?

Related Code:

@interface InfoViewController : UITableViewController {
    NSString *shipAddr;
}
@property (nonatomic,retain) NSString *shipAddr;

@synthesize shipAddr;

VIEWDIDLOAD:

shipAddr = [[[NSString alloc] initWithString:@""] retain];

**CRASHES HERE:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(shipAddr);

Best Answer

You're actually double-retaining the original string, which leaks it, but that's not the cause of your crash.

You're crashing because stringByAppendingString: returns an autoreleased string. So it doesn't matter how many times you retain the original; every time you call stringByAppendingString: (or any of the other stringByWhatever methods) you get a new string that has a limited lifetime.

For your code, I would suggest simply always assigning to self.shipAddr, and just assigning @"" to the string to begin with. The self.shipAddr version will handle memory management for you automatically.

Related Solutions

Ios – Expand and Collapse tableview cells

If you want the cell to get physically bigger, then where you have your store IndexPath, in heightForRow: use:

override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    if selectedIndexPath == indexPath {
      return 230 + extraHeight
    }
    return 230.0
}

Then when you want to expand one in the didSelectRow:

selectedIndexPath = indexPath
tableView.beginUpdates
tableView.endUpdates

Edit

This will make the cells animate themselves getting bigger, you dont need the extra animation blocks in the cell.

Edit 2

 override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        if(selectedIndexPath == indexPath) {
          selectedIndexPath = nil

          if let cell = tableView.cellForRowAtIndexPath(indexPath) as? MyTicketsTableViewCell {
            cell.collapse()
          }
          if let cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow:indexPath.row+1, section: indexPath.section) as? MyTicketsTableViewCell {
            cell.collapse()
          }
        } else {
          selectedIndexPath = indexPath

          if let cell = tableView.cellForRowAtIndexPath(indexPath) as? MyTicketsTableViewCell {
              cell.expand()
          }

          if let cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow:indexPath.row+1, section: indexPath.section) as? MyTicketsTableViewCell {
             cell.expand()
          }
        }

        tableView.beginUpdates()
        tableView.endUpdates()
    }

Best Answer

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Ios – Expand and Collapse tableview cells

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