Hiding/Showing UITableViewCell Accessory Disclosure Indicator

I am trying to load a string from Core Data and if that value in that row equals to "--" the Accessory Disclosure Indicator will hide and the cell selection style should be SelectionStyleNone.

I tried this, but not successful

if (entity.value == @"--"){
    cell.selectionStyle = UITableViewCellSelectionStyleNone;  
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}  

Or

NSString *this = entity.value;
if (this == @"--") {
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    cell.selectionStyle = UITableViewCellSelectionStyleNone;
}

Neither are working, but is this possible though? Thanks.