在UITabBarController / UIViewControllers之间移动值

Question

I have a project i'm working on which involves 3 tabs in a UITabBarController (all done in a storyboard).

Each tab is running off a different view controller.

I have a button on tab 1 that performs a calculation and returns a result in a text box. I want it so that when I hit calculate, the result is also returned in a text box in tab 2.

I'm not really sure how to pass data between UIViewController s so any help is appreciated.

Answer 1

as per vshall says you can do this stuff like bellow:-

yourAppdelegate.h

@interface yourAppdelegate : UIResponder <UIApplicationDelegate,UITabBarControllerDelegate>
{
      NSString *myCalResult;
}
@property (nonatomic,retain) NSString *myCalResult;

yourAppdelegate.m

@implementation yourAppdelegate
@synthesize myCalResult,

yourCalclass.h

#import "yourAppdelegate.h"

@interface yourCalclass : UIViewController
{
yourAppdelegate *objAppdelegate;
}

yourCalclass.m

- (void)viewDidLoad
{
    objAppdelegate = (yourAppdelegate *) [[UIApplication sharedApplication]delegate];
    [super viewDidLoad];
}

-(IBAction)ActionTotal
{
objAppdelegate.myCalResult=result;
}

Now you result stored in objAppdelegate.myCalResult you can use this variable in your another tab with creating object of yourAppdelegat. Hope its helps you

Answer 2

You can define a variable in app delegate and store the result in that variable for class one. And once you switch the class you can fetch that value in your class two by creating an instance of your appDelegate and assign it to your textfield.

As Sanjit has suggested, NSUserDefaults is also a very convenient and clean way to achieve this.

Thanks.

Answer 3

If you don't really need to store the computed value but just notify the other controller in tab2 that the value changed, you can use NSNotificationCenter to post an NSNotification .
When you initialize the controller in tab2 you'll need to add it as an observer of the notification.

Something like that:
in tab1:

NSNumber *value = nil; // the computed value
[[NSNotificationCenter defaultCenter]
 postNotificationName:@"com.company.app:ValueChangedNotification"
 object:self
 userInfo:@{@"value" : value}];

in tab2: register as an observer (in init or viewDidLoad methods)

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(valueChanged:)
 name:@"com.company.app:ValueChangedNotification"
 object:nil];

the method that will be called when the notification is posted:

- (void)valueChanged:(NSNotification *)note
{
    NSDictionary *userInfo = note.userInfo;
    NSNumber *value = userInfo[@"value"];
    // do something with value
}

Don't forget to remove the controller from the observers in viewDidUnload or sooner:

[[NSNotificationCenter defaultCenter] removeObserver:self];