iOS/objective-c: Pass object to new view controller

Question

I am launching a modal view controller in code and wish to pass along a data object. I have created a property on the destination VC for the object. The new VC is launching fine but not getting the data object. Is there anything wrong with the following code? If not, I will have to look for error somewhere else but wondering if this is right way to pass data object.

//in header file of destination VC
@property (nonatomic, strong) Product *product;

//in .m file of starting VC
- (void) gotoStoryboard {
    UIStoryboard *storyBoard = self.storyboard;
    moreInfoVC *infoVC =
    [storyBoard instantiateViewControllerWithIdentifier:@"moreInfo"];
      infoVC.product = _product;//IS THIS ADEQUATE TO PASS DATA OBJECT?
     UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController: infoVC];
    [self presentModalViewController:nav animated:YES];
}

Answer 1

Yes, your code I think works, look for error somewhere else.
But still, 2 things to make sure:

• The gotoStoryboard is implemented after user operation.
• In StoryBoard the moreInfoVC has the Identifier moreInfo .

Answer 2

在发送到目标控制器之前，请先检查_product是否包含某些内容。

Answer 3

In our code we tend towards letting the storyboard define the segue and then just executing this inside a button action:

performSegueWithIdentifier("Segue id", sender: self)

Or alternatively directly link the segue to a button in the story board.

Then we override prepareForSegue like this:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "Segue id" {
        let destinationController = segue.destinationViewController as? MyControllerClass
        destinationController?.someProp = aValue
    }
}

We rarely actually instantiate a view controller from the storyboard manually as your example does. If you have no luck, you could try this approach.

Answer 4

You should use the prepareForSegue Storyboard delegate.

First you call the view to move to the next view via a segue identifier like this:

[self performSegueWithIdentifier:@"YourSegueIdentifier" sender:self];

Then you add this code in the same .m file as the code above. This prepares the next view with the data or items you want it to have.

-(void)prepareForSegue:(UIStoryboard *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"YourSegueIdentifier"]) {
        MoreInfoViewController * moreInfoVC = segue.destinationViewController;
        // This is how you will pass the object or data you want for the next view
        moreInfoVC.aStringToPass = @"I am passing this string";
        moreInfoVc.myCustomObjectToPass = theCustomObject;
    }
}

Then you must have the object as a property in the .h file of the view that you are going to with the segue.

// MoreInfoViewController.h
@property NSString * aStringToPass;
@property CustomObject * myCustomObjectToPass;