Passing plist Items between views with a flip transition

Question

Dear developers,
My question is a simple one, but the background around it can appear a bit complicated - please bear with me!
I have an app with two views; a flip transition allows navigation between them. In each view there is a UILabel - these display strings from a plist. The first View displays 'Question' strings and the second View displays 'Answer' strings.
The plist is structured as follows.
Root................................................(Array)
.............Item 0.................................(Dictionary)
.........................Question...................(String) "Question0?"
.........................ItemChild..................(Dictionary)
.....................................Answer.........(string) "Answer0"
.............Item 1.................................(Dictionary)
.........................Question...................(String) "Question1?"
.........................ItemChild..................(Dictionary)
.....................................Answer.........(string) "Answer1"
.............Item 2.................................(Dictionary)
.........................Question...................(String) "Question2?"
.........................ItemChild..................(Dictionary)
.....................................Answer.........(string) "Answer2"
In the first View there is a button that allows the user to navigate down the Items to view a desired Question/string. On flipping to the second view the itemChild Answer/strings are revealed. This works fine.
On flipping back to the first view however, the Item0 strings are displayed and i don't want this to happen!. Instead I would like the most recent item string to be retained/passed, so that on returning to the first view, the previously selected item question is displayed.
E.g. View 1 (displays Item2/Question2) ---> flip Transition --> View 2 (displays ItemChild/Answer2) --->flip Transition ----> View 1 (displays Item2/Question2)
I have tried to make this work by using the following code;
@secondViewController
- (IBAction)done {
NextItemViewController *controller = [[NextItemViewController alloc] initWithNibName:@"NextItemViewController" bundle:nil];
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
controller.Question = [[self. flashCards objectAtIndex:counter]objectForKey:@"Question"]; <-- i thought this might pass on the Item index position to the firstView
[self presentModalViewController:controller animated:YES];
[controller release];
but i think this is being ignored when the first view is reloaded.
how can i get this working?
the code is presented below and the source code for this project is here; http://rapidshare.com/files/408592175/NextItem_2.zip
Should you require further clarification (if the above doesn't make sense)- please get in touch.
with thanks
james
_first View (NextItemViewController.h)_
#import <UIKit/UIKit.h>
@interface NextItemViewController : UIViewController {
NSMutableArray *flashCards;
IBOutlet UILabel *Label1;
int counter;
@property (nonatomic, retain) NSMutableArray *flashCards;
@property (nonatomic, retain) UILabel *Label1;
@property (nonatomic, assign) int counter;
- (IBAction)NextItem;
-(IBAction)Flip;
@end
_First View (NextItemViewController.m)_
#import "NextItemViewController.h"
#import "FlippedViewController.h"
#import "Constants.h"
@implementation NextItemViewController
@synthesize Label1, flashCards, counter;
/////////////////////Code to load the Array into the UIlable////////////////////////////////////////////////
- (void)viewDidLoad {
[super viewDidLoad];
NSString *path = [[NSBundle mainBundle] pathForResource:@"FlashCardData" ofType:@"plist"];
NSMutableArray* tmpArray = [[NSMutableArray alloc]initWithContentsOfFile:path];
self.flashCards = tmpArray;
if ([flashCards count]) { // <-- handle null plist
NSDictionary *Question = [flashCards objectAtIndex:counter];
Label1.text = [Question objectForKey:Question_KEY];
else {
Label1.text = @"No Questions";
[tmpArray release];
///////////////////////////code to load Next item from UIbutton press/////////////////////////////////////
-(IBAction)NextItem {
int count = [flashCards count];
if (++counter < count) { // <-- any cards left?
NSDictionary *nextItem = [self.flashCards objectAtIndex:counter];
Label1.text = [nextItem objectForKey:Question_KEY]; // <-- use #define here
else {
Label1.text = @"Done"; // <-- no more cards
//////////////////////////code to flip views///////////////////////////////////////////////////////////////
- (void)FlippedViewDidFinish:(FlippedViewController *)controller {
[self dismissModalViewControllerAnimated:YES];
- (IBAction)Flip {
FlippedViewController *controller = [[FlippedViewController alloc] initWithNibName:@"FlippedViewController" bundle:nil];
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
controller.ItemChild = [[self. flashCards objectAtIndex:counter]objectForKey:@"ItemChild"];
[self presentModalViewController:controller animated:YES];
[controller release];
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
- (void)dealloc {
[Label1 release];
[flashCards release];
[super dealloc];
@end
_secondView (flippedViewController.h)_
@interface FlippedViewController : UIViewController {
NSDictionary *ItemChild;
IBOutlet UILabel *Label2;
@property (nonatomic, retain) NSDictionary *ItemChild;
@property (nonatomic, retain) UILabel *Label2;
- (IBAction)done;
@end
Second View (flippedViewController.m)
#import "FlippedViewController.h"
#import "NextItemViewController.h"
#import "Constants.h"
@implementation FlippedViewController
@synthesize Label2, ItemChild;
- (void)viewDidLoad {
[super viewDidLoad];
Label2.text = [ItemChild objectForKey:Answer_KEY];
- (IBAction)done {
NextItemViewController *controller = [[NextItemViewController alloc] initWithNibName:@"NextItemViewController" bundle:nil];
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
- (void)viewDidUnload {
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
- (void)dealloc {
[ItemChild release];
[Label2 release];
[super dealloc];
@end

Answer 1

james_coleman01 wrote:
I have tried to make this work by using the following code;
@secondViewController
- (IBAction)done {
NextItemViewController *controller = [[NextItemViewController alloc] initWithNibName:@"NextItemViewController" bundle:nil];
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
controller.Question = [[self. flashCards objectAtIndex:counter]objectForKey:@"Question"];
[self presentModalViewController:controller animated:YES];
[controller release];
but i think this is being ignored when the first view is reloaded.
The first view is never reloaded and never re-appears, James. The above method creates a new instance of NextItemViewController and presents its view modally. In other words, The first instance of NIVC is the parent of the first instance of FVC, which is the parent of the second instance of NIVC and so on. Each time you do a Flip->Back cycle you add new instances of NIVC and FVC to a growing "stack" of modal view controllers, none of which are ever released.
Since your intent in 'done' is to return to the parent of the modal view, all you need to do there is send a dismissModalViewController message to the parent controller (whose address is always stored in the 'parentViewController' property of the child modal view controller). So this is all you need:
- (IBAction)done {
[self.parentViewController dismissModalViewControllerAnimated:YES]; // <-- back to parent view
Since you already had 'FlippedViewDidFinish' in the parent, the following example code uses that method instead of the code above. Both examples do exactly the same thing in this case.
// NextItemViewController.h
#import <UIKit/UIKit.h>
@class FlippedViewController;
@interface NextItemViewController : UIViewController {
- (void)FlippedViewDidFinish:(FlippedViewController *)controller; // <-- add declaration
@end
// NextItemViewController.m
@implementation NextItemViewController
- (IBAction)Flip {
if (counter >= [flashCards count]) // <-- valid card?
return;
@end
// FlippedViewController.m
@implementation FlippedViewController
- (IBAction)done {
[(NextItemViewController*)self.parentViewController FlippedViewDidFinish:self]; // <-- back to parent view
@end
This second example also includes protection against calling 'Flip' with an invalid array index (i.e. when the deck is empty and "done" is displayed). You might consider disabling the "ItemChild" button in that case, and similarly disabling the "Next Item" button when the deck is empty, but I guess those decisions will depend on whether you want to automatically roll the counter back to 0, etc. I generally hard code array index protection even when it's "impossible" to access the array with an out-of-range index from the UI.
- Ray