Using delegates and protocols to pass data between two views (tabs)

Question

I'm new in Objective-C and I'm making an app that has two tabs. One tab is where I read out the accelerometer and gyroscope and display this values with labels and progress bars, the second tab is were I can make some network setting like IP, Port, there's also a textfield for logs.

After some searching I found that the best option to pass data from my settings tab (NetworkViewController) and the first tab (MotionViewController) is to use delegates and protocols.

This is my NetworkViewController.h:

@protocol ViewControllerNetworkDelegate <NSObject>
- (void)PassDataToViewController:(NetworkViewController *)controller didFinishEnteringItem:(NSString *)item;
@end

@interface NetworkViewController : UIViewController

@property (nonatomic, weak) id<ViewControllerNetworkDelegate> delegate;

@property (strong, nonatomic) IBOutlet UITextField *addressField;
@property (strong, nonatomic) IBOutlet UITextField *portField;
@property (strong, nonatomic) IBOutlet UITextView *logField;

- (IBAction)toggleUDP:(id)sender;
- (IBAction)hideKeyboard:(id)sender;

@end

Fixed: I get an error on the method PassDataToViewController saying "Expected a type".

In my implementation file I have the following code in the method hideKeyboard so it gets exetuded when I change the textfield for the IP-address:

NSString *itemToPassBack =addressField.text;
[self.delegate PassDataToViewController:self didFinishEnteringItem:itemToPassBack];

MotionViewController.h:

#import "NetworkViewController.h"

@interface MotionViewController : UIViewController <ViewControllerNetworkDelegate>

MotionViewController.m

- (void)viewDidLoad
{
NetworkViewController *networkViewController = [[NetworkViewController alloc] initWithNibName:@"MotionViewController" bundle:nil];
networkViewController.delegate = self;
[self pushViewController:networkViewController animated:YES];
}

- (void)PassDataToViewController:(id)controller didFinishEnteringItem:(NSString *)item{
NSString *host= item;
}

This is the relevant code I my project, it's based on this post Passing Data between View Controllers.

I get following error: No visible @interface for 'MotionViewController' declares the selector' pushViewController animated
On [self pushViewController:networkViewController animated:YES]; in MotionViewController.h

Many thanks in advance

Could you solve you problem using my answer and the comments? — Johannes Lumpe, May 10 '12 at 07:05

score 0 · Answer 1 · answered May 09 '12 at 20:25

0

You need to forward declare your NetworkViewController before using it in your protocol inside your header file, using

@class NetworkViewController;

This way the compiler knows about the class you are using before you are actually declaring it.

answered May 09 '12 at 20:25

Johannes Lumpe

1,762
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16

Thanks, the error is fixed, now I can build. But the string isn't passed, I'm missing something. Do you know what? – user1385531 May 09 '12 at 20:40
Did you put an Nslog statement inside the function where you are sending the string to see if it actually gets called? – Johannes Lumpe May 09 '12 at 20:46
No, but I used the debugger. When I make a change in the textfield the function gets executed. – user1385531 May 09 '12 at 20:53
Did you try to log the function you are calling inside MotionController? Because in your snippet you are just assigning "item" to the local variable "host" which will be removed at the end of the function. – Johannes Lumpe May 09 '12 at 20:58
But the function in MotionViewController doesn't get called. So I think something is missing. – user1385531 May 09 '12 at 20:59
Did you actually set the delegates? – Johannes Lumpe May 09 '12 at 21:02
How and where do I have to do that? – user1385531 May 09 '12 at 21:12
Right after you allocate both controllers in code use [controller1 setDelegate:controlller2] and vice versa. – Johannes Lumpe May 10 '12 at 04:47
Thanks for your help but I fixed it on an other way. – user1385531 May 10 '12 at 11:30

Using delegates and protocols to pass data between two views (tabs)

1 Answers1