CODEWITHSUNDEEP
iosobjective-ciphone
user3192186
user3192186

Reputation: 63

Need help transferring data between ViewControllers

I want to keep my project better organized and instead of overloading my Appdelegate with data that I want to transfer from viewcontroller to viewcontroller I want to create a model class to help keep things more organized. However, when using models I am having a hard time transferring data between controllers. Can you show me the error of my ways when trying to transfer this nsstring data from ViewController1 to ViewController2? P.S. I made this example up , because my real project is a little bit more messy so I apologize in advance for any inconsistencies. The following results in NSLog reporting null in 

ViewController2.m

ViewController1.m

 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
 ViewController2 *viewController2 =[[ViewController2 alloc]init];
 ViewControllerModel *vcm = [self.array objectAtIndex:indexPath.row];

 NSLog(@"%@",vcm.string) // this will output a number 

[self.navigationController pushViewController:viewController2 animated:YES];
}
// this delegate fetches an array of json data 
-(void)fetchedResults:(NSMutableArray*)arrayList{ 
self.array = arrayList;
}

ViewController2.m

  - (void)viewDidLoad
  {
  ViewControllerModel *vcm = = [[ViewController alloc] init];
  [super viewDidLoad];
  NSLog(@"%@",vcm.string);  // this will output null.
  }

ViewControllerModel .h #import 

  @interface ViewControllerModel : NSObject
  @property (nonatomic, strong) NSString *string;

  @end

ViewControllerModel.m

  #import "ViewControllerModel.h"

  @implementation ViewControllerModel
  @synthesize string;

  @end

MyHandler.m

    //this is where vcm.string in ViewController1.m will get all the numbers not sure if this is needed but just in case .

   for (NSDictionary *dict in responseArray)
   {
   ViewControllerModel *vcm = [[ViewControllerModel alloc] init];

   vcm.string = ([dict valueForKey:@"string"] == [NSNull null]) ? @"" : [NSString stringWithFormat:@"%@",[dict valueForKey:@"string"]];

Upvotes: 1

Views: 68

Answers (1)

Jesse
Jesse

Reputation: 1697

Make the following changes:

ViewController1.m

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    ViewController2 *viewController2 =[[ViewController2 alloc]init];
    ViewControllerModel *vcm = [ViewControllerModel alloc] init];
    vcm.string = @"My String";
    viewController2.vcm = vcm;

    NSLog(@"%@",vcm.string) // this will output a number 
    [self.navigationController pushViewController:viewController2 animated:YES];
}

// this delegate fetches an array of json data 
- (void)fetchedResults:(NSMutableArray*)arrayList{ 
    self.array = arrayList;
}

ViewController2.h

@interface ViewController2 : NSObject
@property (nonatomic, strong) ViewControllerModel *vcm;
@end

ViewController2.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"%@", self.vcm.string);
}

I would also recommend the following improvements.

  1. You don't really need a model object at this point. You could just add the string as an NSString property to ViewController2 instead of the ViewControllerModel object:

    @property (nonatomic, copy) NSString *string;

  2. I would recommend naming your properties, model object and view controllers to something more descriptive. Even if it's a sample it will be hard to understand it if you don't.

  3. When you create an NSString property (or any other class that has a mutable equivalent) I'd recommend using 'copy' instead of 'strong'. This will make an immutable copy of the string if an NSMutableString is assigned to the property which is considered a safer approach.

Upvotes: 1

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