Calling A Variable in a different View Controller iOS

Question

So i have two view controllers home, second. I create a variable in home and want to call it in the second UIViewController. I get an error saying:

Use of undeclared identifier 'plusNumber'

Please let me know why i am not connecting the second UIViewController with the variable in home. I imported the header file home.h into the second.h file.

Thanks.

Code is below: home.h

@interface homeViewController : UIViewController <UIAlertViewDelegate>
{
    int plusNumber;  
}
- (IBAction)plusSign:(id)sender;

home.m

- (IBAction)plusSign:(id)sender {

    if(self.plusNumber == 0)
    {
        self.plusNumber = @"1";
    } 
    else 
    {
        self.plusNumber = @"0";
    }

}

second.h

#import "home.h"

@property (weak, nonatomic) IBOutlet UILabel *output;

second.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.output.text = [NSString stringWithFormat:@"%i", plusNumber];
}

You will need to create @property in home.h to access this in other VC. `@property (nonatomic) int plusNumber;` — Yogesh Suthar, Jul 08 '14 at 03:38
possible duplicate of [Passing Data between View Controllers](http://stackoverflow.com/questions/5210535/passing-data-between-view-controllers) — Yogesh Suthar, Jul 08 '14 at 03:42

score 1 · Answer 1 · edited May 23 '17 at 11:50

1

You must declare it as a public variable

So you must change your home.h interface to

@interfacehomeViewController : UIViewController <UIAlertViewDelegate>
 {
  @public
  int plusNumber;  
 }

more info: How to access @public instance variable from another class in Objective-C?

edited May 23 '17 at 11:50

Community

1
1

answered Jul 08 '14 at 03:43

Jack C

1,044
2
12
22

I have tried both suggestions and am stilling getting the same error message. I read through the links as well and think that i am doing what they say to do but it still says Use of undeclared identifier 'plusNumber'. – user3806600 Jul 08 '14 at 03:53

score 0 · Answer 2 · answered Jul 08 '14 at 04:08

0

Use properties.

@interface HomeViewController : UIViewController
@property (nonatomic) int plusNumber;
@end

answered Jul 08 '14 at 04:08

CrimsonChris

4,651
2
19
30

score 0 · Answer 3 · answered Jul 08 '14 at 05:26

In home.m, create a segue from view1 to view2 and give it a segueIdentifier Import second.h inside home.h file

- (IBAction)plusSign:(id)sender {

if(self.plusNumber == 0)
{
    self.plusNumber = @"1";
[self performSegueWithItentifier @"segueName"];
} 
else 
{
    self.plusNumber = @"0";
   [self performSegueWithItentifier @"segueName"];
}

}


-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
  Second secondInstance = [segue destinationViewController];
secondInstance.output = self.plusNumber;

}

In Second.h remove the import statement or it will get into a memory leak cycle Make one NSString named @property(nonatomic,strong) NSString *outputStr;

 viewDidLoad{
   self.output.text = self.outputStr;
   }

and voila hope it helps

score 0 · Answer 4 · answered Jul 08 '14 at 05:49

home.h

@property (nonatomic) int plusNumber;

home.m

- (IBAction)plusSign:(id)sender {
   [self performSegueWithItentifier @"segue"];
}


-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
    if([segue.identifier isEqualToString:@"segue"]){
        SecondViewController *controller = 
                         (SecondViewController *)segue.destinationViewController;
        controller.plusNumberString  = (self.plusNumber == 0) ?  @"1" :  @"0";
    }
}

second.h

@property (nonatomic, copy) NSString *plusNumberString;

second.m

-(void)viewDidLoad{
    NSLog(@"_plusNumberString = %@", _plusNumberString);
}

score 0 · Answer 5 · answered Jul 08 '14 at 06:53

In Objective C, way of coding we call this as getter & setters.

You can create your getters and setters by declaring the property to the variable. Since you're using int datatype, just assign it as below

@Property(nonatomic, assign) int plusNumber

HomeViewController.h

@interface homeViewController : UIViewController <UIAlertViewDelegate>
{
    int plusNumber;  
}
@Property(nonatomic, assign) int plusNumber
- (IBAction)plusSign:(id)sender;

SecondViewController.m

#import "homeViewController.h"

- (void)viewDidLoad
{
    [super viewDidLoad];
    homeViewController *homecontroller = [[homeViewController alloc] init]
    self.output.text = [NSString stringWithFormat:@"%i", homecontroller.plusNumber];
}

score 0 · Answer 6 · answered Jul 08 '14 at 08:39

HomeViewController.h
    @interfacehomeViewController : UIViewController <UIAlertViewDelegate>
     {

      NSUInteger plusNumber;  
     }
     @property (nonatomic,assign) NSUInteger plusNumber;

HomeViewController.m
@synthesize plusNumber;

SecondViewController.m

#import "homeViewController.h"

- (void)viewDidLoad
{
    [super viewDidLoad];
    homeViewController *homecontroller = [[homeViewController alloc] init]
    self.output.text = [NSString stringWithFormat:@"%i", homecontroller.plusNumber];
}

Hope it helps.

Calling A Variable in a different View Controller iOS

6 Answers6

HomeViewController.h

SecondViewController.m