Understanding the Navigation Controller and Passing Data Between View Controllers in Xcode for iOS App Development

As a developer, working with view controllers and navigation controllers is an essential part of creating user interfaces for iOS applications. In this article, we’ll explore how to pass data between view controllers using the navigation controller in Xcode.

A navigation controller is a type of container view controller that helps manage the flow of views within an app. It provides a way to display multiple view controllers on top of each other, with a back button for navigating between them.

When you add a new view controller to your navigation stack, Xcode automatically creates a navigation bar at the top of the screen. This navigation bar contains two buttons: a “Back” button and an “Done” button (if you’re using a modal presentation style). The “Back” button allows users to navigate back to the previous view controller.

In our case, we want to pass data from one view controller (Fraga) to another view controller (Rattning). We’ll use the navigation controller to achieve this.

To set up a navigation controller, you need to add it to your app delegate’s application(_:didFinishLaunchingWithOptions:) method. This method is called when the app launches for the first time.

Here’s an example of how to create and configure a navigation controller:

## Creating a Navigation Controller

First, import the UIKit framework in your app delegate file:
```objectivec
#import <UIKit/UIKit.h>

Next, create an instance of UINavigationController and add your view controller as its root view controller. Here’s how to do it:

-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    Fragap *fraga = [[Fraga alloc] init];
    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:fraga];
    self.window.rootViewController = navController;
    return YES;
}

In this code, Fraga is the view controller that you want to display as the initial view. The navigation controller is created with initWithRootViewController, and its root view controller is set to your Fraga instance.

Passing Data Between View Controllers

To pass data between view controllers, you can use a variety of methods, including:

Properties: Assign a property in one view controller and access it from another.
Notifications: Send a notification from one view controller and receive it in another.
Delegates: Use a delegate protocol to communicate between view controllers.

For our example, we’ll use properties. We’ll add an antalratt property to the Rattning view controller class and assign its value from the Fraga view controller.

Here’s how you can do it:

## Defining a Property in Rattning

In your `Rattning.h` file, define a property called `antalratt`:
```objectivec
#import <UIKit/UIKit.h>

@interface Rattning : UIViewController

@property (nonatomic) NSInteger antalratt;

@end

Next, create an instance variable to store the value of antalratt in your Rattning view controller class:

@implementation Rattning {
    @private
    NSInteger _antalratt;
}

@synthesize antalratt = _antalratt;

-(void)viewDidLoad {
    // ...
    ratttext.text=[[NSString alloc] initWithFormat:@"%d", self.antalratt];
}

In this code, we’ve defined an instance variable _antalratt and assigned its value to the antalratt property.

Passing Data from Fragap to Rattning

To pass data from one view controller to another, you can use a variety of methods. In our case, we’ll create an action in the Fraga view controller that will set the value of antalratt when called.

Here’s how you can do it:

## Creating an Action in Fragap

In your `Fraga.m` file, create an action called `result`:
```objectivec
- (IBAction)result:(id)sender {
    Rattning *rattning = [[Rattning alloc] initWithNibName:@"RattningView" bundle:nil];
    rattning.antalratt = self.antalratt;
    [self.navigationController pushViewController:rattning animated:YES];
}

In this code, we’ve created an action called result and assigned the value of antalratt to its antalratt property.

Linking the Action to a Button

To link the action to a button in your Xcode storyboard, follow these steps:

Select the button in your storyboard.
Control-drag from the button to the action you want to call when it’s tapped.
Release the mouse and select result from the popup menu.

In this code, we’ve linked the result action to a button in our Xcode storyboard.

Conclusion

In this article, we explored how to pass data between view controllers using the navigation controller in Xcode. We used properties to communicate between view controllers and created an action in one view controller that sets its value when called. By following these steps, you can easily pass data between view controllers in your iOS applications.

Additional Resources

Last modified on 2023-06-19