Passing model objects from one view controller to

问题:

I have two UITableViewControllers. One displays a list of names and on tapping any cell will push the second TableViewController which enables the user to edit the name in a UITextField.

Now I am able to pass the name string from the first TableViewController to the second. (I'm doing this by creating a property in the second TableViewController which I'm setting just before pushing the second TableViewController) But how do I pass the edited name string from the second to the first (so that I can update the first table with the edited name)?

回答1:

Create a mutable array property in the first controller, and pass that array and an index to the second controller.

FirstController.h

   @property (nonatomic,retain)     NSMutableArray *myStrings;

FirstController.m

   @synthesize myStrings;

   init {
         self.myStrings = [NSMutableArray arrayWithCapacity:8];
   }


   didSelectRowAtIndexPath {

     SecondVC *vc = [[SecondVC new];
     [self.theStrings addObject:@"Original String"]; // or replaceAtIndex: indexPath.row
     vc.theStrings = self.myStrings;
     vc.theIndex   = indexPath.row;
     //push detail vc.
   }

SecondController.h

  @property (nonatomic, retain) NSMutableArray *theStrings;
  @property (nonatomic        ) int             theIndex;

SecondController.m

  @synthesize theStrings;
  @synthesize theIndex;

  doneEditingMethod {
       [self.theStrings replaceObjectAtIndex: self.theIndex withObject: myNewString];
   }

回答2:

I see mainly three options:

1. you could define your model as a singleton, which is easily accessible from every other object. In this case think about concurrent access to the model, it any;

2. have the model private to the first controller, but instead of passing the string to the second controller, pass a pointer to the model, so you can read and write to it;

3. pass the second controller a pointer to the first, so you can signal it (by calling some specific method); this is ok if you subclass the controller, otherwise you should use a delegate.

A fourth option would be using notifications, but I think that 1 or 2 a the way to go.

回答3:

Maybe you should take a look at the delegate pattern which could save you a lot of time ! :-)

You know it's like using an UITableView datasource. With a delegate (or datasource), you can ask or set informations to a root controller.

Maybe it's the best option ! (so google "objective-c delegate")

Good luck !

回答4:

Are they connected by a navigation controller?

If so, this could solve the problem

// in SecondViewController.m
NSArray* controllers = self.navigationController.viewControllers;
UITableViewController* firstViewController = [controllers objectAtIndex:controllers.count-2];

回答5:

There are several ways to do this. I, personally, use a third-party class to house strings and just reference that class as I move between UITableViews.