iPhone: passing data between views - objective-c

Question

I'm trying to create a simple application to understand how to pass data between views. I have two views. The first one passes some strings to the second view with this method:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"colorSegue"]) {
[segue.destinationViewController setFirstColor:self.favoriteColorTextField.text];
[segue.destinationViewController setSecondColor:self.secondColor];
[segue.destinationViewController setDelegate:self];
}
And the second view receives the data with this method.
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (self.firstColor != nil && ![self.firstColor isEqualToString:#""]) {
self.favoriteColorLabel.text = [[NSString alloc] initWithFormat:#"Favorite color: %#", self.firstColor];
}
if (self.secondColor != nil && ![self.secondColor isEqualToString:#""]){
self.secondFavoriteColorLabel.text = [[NSString alloc] initWithFormat:#"Second favorite color: %#", self.secondColor];
}
}
Till now everything works fine, the second view visualizes the first string (but not the second one, because it's still empty). Then the second view passes back a string to the first one through delegation:
- (void)viewWillDisappear:(BOOL)animated
{
[self.delegate setSecondFavoriteColor:self.secondFavoriteColorTextField.text];
}
And the first view visualizes the string like this:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (self.secondColor != nil && ![self.secondColor isEqualToString:#""]) {
self.secondFavoriteColorLabel.text = [[NSString alloc] initWithFormat:#"Second favorite color: %#", self.secondColor];
}
}
Here everything works, the first view visualizes both strings.
But now I'm having a problem. If i try to pass again the strings to the second view, only the first one is passed correctly. The second view always receives secondColor with the nil value, even after its value has been set through delegation.
The variables firstColor and secondColor are declared and synthetized exactly in the same way. Can you please help me find the error?

Answer 1

I think you need to trasform segue.destinationViewController to SecondViewController class
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"colorSegue"]) {
SecondViewController *svc = [segue destinationViewController];
[svc setFirstColor:self.favoriteColorTextField.text];
[svc setSecondColor:self.secondColor];
[svc setDelegate:self];
}
OR
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"colorSegue"]) {
[(SecondViewController *)segue.destinationViewController setFirstColor:self.favoriteColorTextField.text];
[(SecondViewController *)segue.destinationViewController setSecondColor:self.secondColor];
[(SecondViewController *)segue.destinationViewController setDelegate:self];
}

Answer 2

If you want to pass data between more than 1 views then you have these options.
You can use a singleton
Use your AppDelegate.
Here is a good tutorial about singleton:
http://www.galloway.me.uk/tutorials/singleton-classes/
If you want to use AppDelegate to do it like this:
AppDelegate.h
#property (nonatomic, retain) NSString *something;
AppDelegate.m
#synthesize something;
FirstViewController.m
#import "AppDelegate.h";
(void) setSomething {
AppDelegate *AppDelegate = [[UIApplication sharedApplication] delegate];
AppDelegate.something = #"something";
}
SecondviewController.m
#import "AppDelegate.h";
(void) getSomething {
AppDelegate *AppDelegate = [[UIApplication sharedApplication] delegate];
label.text = AppDelegate.something;
}