How to pass a variable from one view controller to another?

I have three view controllers, one root controller, one login view controller and one customers view controller. I want to pass the entered username and password in login view controller to the customers view controller. My files and code is displayed below, could you please guide me, how can access to variables set in the login view controller? Or how can I pass variables to customers view controller?

I have these class files:

/classes/MySoftwareAppDelegate.h
/classes/MySoftwareAppDelegate.m
/classes/ViewController.h
/classes/ViewController.m
/classes/LoginController.h
/classes/LoginController.m
/classes/CustomersController.h
/classes/CustomersController.m

I have these views:

/resources/MainWindow.xib
/resources/Login.xib
/resources/Customers.xib

In the AppDelegate, I have successfully inserted the sub view "Logi开发者_Python百科n" and it's displayed whenever the app starts.

In the login view, I enter my username and password and then click the "Login" button. When this button is clicked, an IBAction is triggered. In this IBAction, I want to change the current subview with the Customers.

Here's the code I have used:

MySoftwareAppDelegate.h

#import <UIKit/UIKit.h>

@class ViewController;

@interface MySoftwareAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
 ViewController *viewController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet ViewController *viewController;

@end

MySoftwareAppDelegate.m

#import "MySoftwareAppDelegate.h"
#import "ViewController.h"

@implementation MySoftwareAppDelegate

@synthesize window;
@synthesize viewController;


- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after application launch
 [window addSubview:viewController.view];
    [window makeKeyAndVisible];
}


- (void)dealloc {
 [viewController release];
    [window release];
    [super dealloc];
}


@end

ViewController.h

#import <UIKit/UIKit.h>

@class LoginController;

@interface ViewController : UIViewController {
 LoginController *loginController;
}

@property (nonatomic, retain) LoginController *loginController;

@end

ViewController.m

#import "ViewController.h"
#import "LoginController.h"

@implementation ViewController

@synthesize loginController;

- (void)viewDidLoad {
 LoginController *tmpViewController = [[LoginController alloc] initWithNibName:@"Login" bundle:nil];

 self.loginController = tmpViewController;
 [self.view insertSubview:loginController.view atIndex:0];

 [tmpViewController release];

    [super viewDidLoad];
}

- (void)didReceiveMemoryWarning {
 // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

 if (self.loginController.view.superview == nil) {
  self.loginController = nil;
 }

 // 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 {
 [loginController release];
    [super dealloc];
}

@end

LoginController.h

#import <UIKit/UIKit.h>

@class CustomersController;

@interface LoginController : UIViewController {
 UIButton *loginButton;
 UITextField *usernameTextField;
 UITextField *passwordTextField;
 NSMutableString *available_credits;
 NSString *current_xml_element;
 CustomersController *customersController;
}

@property (nonatomic, retain) IBOutlet UIButton *loginButton;
@property (nonatomic, retain) IBOutlet UITextField *usernameTextField;
@property (nonatomic, retain) IBOutlet UITextField *passwordTextField;
@property (nonatomic, retain) NSMutableString *available_credits;
@property (nonatomic, retain) NSString *current_xml_element;
@property (nonatomic, retain) CustomersController *customersController;

-(IBAction)textFieldDoneEditing:(id)sender;
-(IBAction)backgroundTap:(id)sender;
-(IBAction)loginToAccount:(id)sender;

@end

LoginController.m

#import "LoginController.h"
#import "CustomersController.h"

@implementation LoginController

@synthesize loginButton;
@synthesize usernameTextField;
@synthesize passwordTextField;
@synthesize customersController;

- (void)viewDidLoad {
 UIImage *buttonImageNormal = [UIImage imageNamed:@"whiteButton.png"];
 UIImage *stretchableButtonImageNormal = [buttonImageNormal stretchableImageWithLeftCapWidth:12 topCapHeight:0];
 UIImage *buttonImagePressed = [UIImage imageNamed:@"blueButton.png"];
 UIImage *stretchableButtonImagePressed = [buttonImagePressed stretchableImageWithLeftCapWidth:12 topCapHeight:0]; 

 [loginButton setBackgroundImage:stretchableButtonImageNormal forState:UIControlStateNormal];
 [loginButton setBackgroundImage:stretchableButtonImagePressed forState:UIControlStateHighlighted];
}

- (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 {
 [usernameTextField release];
 [passwordTextField release];
    [super dealloc];
}

-(IBAction)textFieldDoneEditing:(id)sender {
 [sender resignFirstResponder];
}

-(IBAction)backgroundTap:(id)sender {
 [usernameTextField resignFirstResponder];
 [passwordTextField resignFirstResponder];
}

-(IBAction)loginToAccount:(id)sender {

 // bla bla bla... Login check process is done here

 CustomersController *tmpViewController = [[CustomersController alloc] initWithNibName:@"Customers" bundle:nil];
 self.customersController = tmpViewController;

 [self presentModalViewController:tmpViewController animated:YES];
 [self.view removeFromSuperview];

 [tmpViewController release];

}

@end

As you can see above, in LoginController.m's loginToAccount method, I am checking the login info and then setting the new view controller for the "customers" sub-view.

Then I am removing the current "Login" subview from the super view but don't know how to add the new "Customers" sub view.

In MainWindow.xib, I have one view controller which is linked to ViewController class and it's the root contoller.

Any help is appreciated. Because I am new to Objective-C and iPhone programming, please do your best to explain considering a novice programmer :)

Thanks again.

Okay, let me answer my question. I just found the answer on StackOverFlow.com

In the view controller which is going to load the next view controller, just add these lines:

NextController *tmpViewController = [[NextController alloc] initWithNibName:@"NextView" bundle:nil];
tmpViewController.enteredUsername = usernameTextField.text;
tmpViewController.enteredPassword = passwordTextField.text;     

I'd say that better way is to have separate class for storing globally needed data (and that would be compliant with MVC model). For example you can store you login information in your MySoftwareAppDelegate, which is easily accessible with [[UIApplication sharedApplication] delegate] call from any part of your application.

It all depends on how serious the data you want to pass it. For a quick variable (maybe a settings change in a modal view controller) TamTam's solution makes the most sense. You alloc/init'ed it, you got the variable, why not access it properties? That same (modally presented) view controller might pass variables back via a delegate pattern.

If you're data needs to be system wide, you can use the singleton pattern. Using "[[UIApplication sharedApplication] delegate]" gets the application delegation (which is a singleton), and many people stuff their variables there for convenience. However, your app delegate wasn't designed for this, and so it's considered bad form. Create your own singleton if your apple isn't a quickie.

If you use a persistent data store like sql, plists or coredata, you can put your system wide data there.