如何通过prepareForSegue编辑我的segue目标数据？

Question

I am trying to edit the segue's target's data through prepareForSegue , but everything I try keeps returning the "unrecognized selector sent to instance ..." error. Is there a special way to edit my target's data, is it being deleted before I edit it or something like that? I just started picking this stuff up so I still don't have my head all the way around it. Here is a sample of some of my code

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:@"managerSegue"]){
    ASExpenseList *target = [segue destinationViewController];
    NSIndexPath *row = [self.tableView indexPathForSelectedRow];
    self.cellPressed = row.row;

    switch(self.cellPressed){
        case 0:
            [target initWithData:self.oneTimeExpenses]; //PROBLEM LINE
           // target.expenses = [[NSMutableArray alloc] initWithArray:self.oneTimeExpenses]; ALSO PROBLEM
            target.title = @"One-Time"; //not breaking the program but not working

The ASExpenseList function I'm calling is really simple:

-(void) initWithData:(NSMutableArray *)newExpenses {
self.expenses = newExpenses;
[self.tableView reloadData];
}

So I am trying to set the target's data to some data I already have, and I am trying to dynamically change the title. The title change isn't working and the data lines are throwing errors. I'm guessing that I just misunderstand how it works, so any help or clarification would be awesome. Thanks!

Answer 1

When you perform a segue, the storyboard handles the alloc + init of a UIViewController, so you don't need to do the initialization. You can set data by using the properties.

Answer 2

Can you show the actual "unrecognized selector sent to instance ..." error you're getting? Different things can be going wrong here depending on what selector is being sent to what object.

But generally, when you're dealing with "unrecognized selector", step 0 is to determine if the object is really what you think it is. In this case, make sure [segue destinationViewController] really is an ASExpenseList . I have my doubts, as ASExpenseList sounds like a model or a view, and [segue destinationViewController] as the name implies, returns a view controller.

Some strategies for verifying the identity of the destinationViewController include:

• NSLog("dest: %@", [segue destinationViewController]);
• NSLog("dest class: %@", [segue destinationViewController]);
• Placing a breakpoint and examining target in Variables View.
• Placing a breakpoint and interrogating target with po in LLDB.

Answer 3

Add the newExpenses as a property in your ASExpenseList class. Set it in your prepareForSegue and populate the tableView in your viewDidLoad in ASExpenseList using the NSArray you passed.