CODEWITHSUNDEEP
iphoneobjective-c
jroyce
jroyce

Reputation: 2148

How do I pass object from one ViewController to another ViewController

I have a RootViewController that calls an AddQuoteViewController and there is a variable "subject_id" that I set in the RootViewController that does not show up in AddQuoteViewController and I need help understanding why and how to fix it. 

    Subject *sub = [self.tableDataSource objectAtIndex:indexPath.row];

    self.subject_id = sub.subject_id;

    [self addQuote_Clicked: sub];

...

- (void) addQuote_Clicked:(id)sender {

    if(aqvController == nil)
        aqvController = [[AddQuoteViewController alloc] initWithNibName:@"AddQuoteView" bundle:nil];

    if(addNavigationController == nil)
        addNavigationController = [[UINavigationController alloc] initWithRootViewController:aqvController];

    [self.navigationController presentModalViewController:addNavigationController animated:YES];
}

Then in my AddQuoteViewController I try to access this variable like this: 

RootViewController *rv = [RootViewController alloc] ;

NSLog(@"rv.Subject_id = %d", rv.subject_id);

But get nothing. There must be a simple way to do this.

Upvotes: 0

Views: 1479

Answers (3)

gamozzii
gamozzii

Reputation: 3921

There are various ways of doing this, but a short answer - You can set a reference to the RootViewController as a property on your AddQuoteViewController

i.e.

in AddQuoteViewController.h

RootViewController *rvc

...

@property (nonatomic,assign) RootViewController *rvc;

and corresponding synthesize and release in your implementation class. (AddQuoteViewController.m)

Then when you create your AddQuoteViewController inside your RootViewController, also set this property:

- (void) addQuote_Clicked:(id)sender {

    if(aqvController == nil)
        aqvController = [[AddQuoteViewController alloc] initWithNibName:@"AddQuoteView" bundle:nil];
    aqvController.rvc = self;
... etc.

Then you can access any property of the root view controller inside your AddQuoteViewController via this property:

NSLog(@"rv.Subject_id = %d", self.rv.subject_id);

As a side note there are a few things you are doing in your question that are a bit unusual, like trying to get a reference to an object by allocating a new one, and also creating a new navigation controller and presenting it as a modal view controller typically you would do one or the other (and wouldn't need to create a new navigation controller). i.e. you would either create a view controller and present it modally, or you would create a view controller and push it onto your current navigation controller stack.

Upvotes: 1

Tom Hamming
Tom Hamming

Reputation: 10961

First of all, there's an error in your third block of code. This:

RootViewController *rv = [RootViewController alloc] ;

Should be this:

RootViewController *rv = [[RootViewController alloc]init];

But strictly speaking that's not why you aren't seeing your instance variable.

If I understand correctly, the first two blocks of code are in RootViewController, and they instantiate an AddQuoteViewController and present it. Then, from your third block of code, which is in AddQuoteViewController, you want to access a member variable (subject_id) of the RootViewController that brought it up.

The approach of instantiating a RootViewController from within the AddQuoteViewController wouldn't work, because you're creating a different instance of RootViewController. What you're after is the value in the instance you just came from.

Perhaps the easiest way to do it is to create a corresponding property on AddQuoteViewController and set it when it's created:

- (void) addQuote_Clicked:(id)sender {

if(aqvController == nil)
    aqvController = [[AddQuoteViewController alloc] initWithNibName:@"AddQuoteView" bundle:nil];

if(addNavigationController == nil)
    addNavigationController = [[UINavigationController alloc] initWithRootViewController:aqvController];

aqvController.subject_id = self.subject_id;

[self.navigationController presentModalViewController:addNavigationController animated:YES];
}

You'll need to create the subject_id property on AddQuoteViewController the same way you did on RootViewController.

Upvotes: 2

Darren
Darren

Reputation: 10398

You can't access variables across view controllers like that. Have a look at creating a singleton class which will be globally accessible. One exception I think is you can access them in the AppDelegate, but it's not advisable to have global vars.

Upvotes: 1

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