i'm turning around for days.
I've got a hierarchy of 3 ViewControllers.
Start in VC1, from there you can load VC2. In VC2 you can load VC3.
My navigation works fine VC1->VC2->VC3 and the same backwards.
VC3 allows the user to go back to VC1.
I wonder if it's possible to tell VC3 that VC1 is now it's delegate.
It would work fine with VC2 but I'd like to use the datas saved in VC3 in VC1.
Create a delegate to pass value from one class to another.
Then set delegate in both VC1 and VC2 where VC1 recieves from VC2 and VC2 recieves from VC3
Then call for delegate from VC3 and pass value to VC2 .In VC2 the called method implement the invocation of its delegate to VC1 and the value is there in vc1
VC3-->del-->VC2-->del->VC1
If VC1 is the delegate of VC2, you could just assign VC2's delegate property to the delegate property of VC3
In your VC2 #implementation before VC3 is pushed onto the navigation stack:
vc3Instance.delegate = self.delegate
I suggest adding a weak property called 'master' for example in each view controller and make it point to the view controller that presented it. Once you do that, you can then reach VC1 (and all it's data) from VC3 in the following way:
VC1ViewController *vc1 = self.master.master;
Related
Now I have 3 Viewcontrollers like this:
HomeViewcontroller = VC1.
Viewcontroller2 = VC2 --> has a table view with cells on it.
Viewcontroller3 = VC3 --> allows me to edit each cell in VC2 or delete.
I am using NavigationController between Viewcontrollers, to get the nice "back" button :)
Lets say I am in VC1, I press a button and I go to VC2.
Now let's say I have 4 cells.
I press cell number 2 and I go to VC3, where I can edit what I have in the cell or even delete it.
This is all working OK (tested it).
Let's say I want to delete that cell. I have a button on VC3 and I use it and I delete the cell (this is tested and also working OK).
Now when I do this I push into VC2 again like this:
let viewController = storyboard?.instantiateViewController(withIdentifier: "VC2") as! VC2!
self.navigationController?.pushViewController(viewController!, animated: true)
The problem is that when I do this I go to VC2 but I doesn't reload my tableView has it should (the erased cell it's still there).
To fix this I tried adding some code in VC2, in the viewDidLoad:
self.tableView.reloadData()
Now I managed to do it work. I mean when I delete a cell from VC3 I am pushed to VC2 and the cell it's not there. However If I press the back button it takes me to the previous cell that I have deleted,,, If the cell doesn't exist anymore I don''t want it to take me there. I want it to take me to the VC1 (home).
How can I make this work?
Perhaps I should do this in another way and not pushing like that?
Practically you are doing wrong, when delete / edit operation done on VC3 and you want to come back on VC2, why you are doing pushViewController , you have to apply popViewController.
You have to apply self.navigationController?.popViewController(animated: true) coming back to VC2 from VC3.
Remove
let viewController = storyboard?.instantiateViewController(withIdentifier: "VC2") as! VC2!
self.navigationController?.pushViewController(viewController!, animated: true)
Add
self.navigationController?.popViewController(animated: true)
Also
Put reloadData() method for table view in viewWillAppear. like below code.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.tableView.reloadData()
}
Some reference material to read about UINavigationController.
https://developer.apple.com/reference/uikit/uinavigationcontroller
Put your self.tableView.reloadData() in an override of viewWillAppear. viewDidLoad is only called once after the viewController is created, but viewWillAppear is called every time it is about to appear on screen.
Also, don't use a push to return to VC2 from VC3. You should pop the current viewController.
self.navigationController?.popViewController(animated: true)
Instead of pushing ViewController2 again from ViewController3 you need to create one delegate and implement that delegate within your ViewController2 now create the instance of that delegate in viewController3 and set that delegate when you are moving from ViewController2 to ViewController3. Now when you update or delete data of ViewController2's simply use that delegate to call method from ViewController2 and inside that method update your DataSource and reload the tableView.
N.,
Normally when different view controllers are embedded in a navigation controller, you push up the stack and going back you pop from the stack. As I understand your story it seems you are only pushing new view controllers on the stack.
Your first view controller is VC1. You press a button and you push the new view controller on the stack, VC2. The navigation controller now has 2 view controllers on the stack VC1 and VC2. Then you select a cell in the table view of VC2 and it takes you to VC3.
The navigation controller now holds 3 view controllers on the stack VC1, VC2 and VC3. Now you delete a cell and you push a NEW view controller on the stack, which is again a VC2, but a new one. The navigation controller now has four view controllers on the stack VC1, VC2, VC3 and another instance of VC2.
I would assume you have a model object containing the data in the table views of VC2 and VC3. When you delete the cell you should delete the cell in your model object and not push a new VC2 on the stack, but dismiss the VC3. You can do this with an #IBAction in VC2 to which your delete button is connected. It then pops the VC3 from the stack and you land back in VC2 in the IBAction method to which you have linked the delete button. The navigation controller then only has 2 view controllers on the stack again, VC1 and VC2.
In that IBAction method you can reload the table view and the table view will call the datasource method
tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
This method will look at your model object and not find the deleted data and your cell is gone.
When you then push the back button, the navigation controller pushes the VC2 from the stack and is left with only one view controller VC1. You will land back on your page.
Hope this helps.
I have the base ViewController which i my main menu(VC1).
From there I navigate to another VC which displays a UITable(VC2). From here i can call
[self.parentViewController dismissModalViewControllerAnimated:YES];
To move back to the main menu. That works fine.
If i load another VC(V3) with displays a UIWebView from VC2 and want to jump back to the main menu(VC1), how can this be done in the best way?
So I navigate VC1->VC2->VC3 and then want to jump VC3->VC1.
My app doesn't have a UINavigationViewController or anything like that.
Many Thanks,
-Code
You could try creating a method in the parent vc (vc2) that you call from vc3 that does the following:
-(void)dismissTwo
{
[self dismissModalViewControllerAnimated:NO];
[self.parentViewController dismissModalViewControllerAnimated:YES];
}
That's untested, but give it a shot.
Its tricky if you used navigation controller you could have popped to root view controller using poptorootviewcontroller.
However in your case if you can implement a delegates for VC2 and VC3. In the delegate for VC3 in VC2 dismiss VC3 and call delegate of VC2 which is implemented in VC1.
So basically the flow is as follows
Create VC1
When you create VC2 from VC1 assign delegate to VC1
When you create VC3 from VC2 assign delegate to VC2
From this point on you can pass messages in a cleaner way between the view controllers.
For sake of simplicity I have 3 UIViewControllers named, vc0, vc1, vc2. My Flow of operations is a button in vc0 calls
[vc0 presentModalViewController:vc1]
Then in vc1 I have another button in vc1 that calls
[vc1 presentModalViewController:vc2]
In both vc1 and vc2 I have an X button that calls
[self dismissModalViewController];
Now the first run threw that flow is fine, vc1 is presented modally, followed by vc2 after the correct button presses. Dismissing the views also behaves correctly. However, when I attempt to start the flow all over again I'm unable to present vc2 modally from vc1. Has anyone else run into a similar problem before?
I think You might be missing the allot + init for the view controllers that you want to present
Need some best practice advice here...
Navigation based application. Root view is a UITableView where user can drill down to a detail UIViewController (call it VC1). User wants to initiate some task but it may require additional info before it can proceed. If so then VC1 allocs & presents modal VC2 using the "flip" transition holding a strong reference to VC2 in a property.
All fairly standard. Here's where I'm running into trouble. Once user fills out required info in VC2 the app can either continue on to a MFMailComposeViewController or flip back to VC1. If they continue to MailCompose then when that dismisses it should return to VC1.
VC2 has a weak reference to VC1 and the problem arrises when VC2 tries to dismiss itself and present MFMailComposeViewController:
[self dismissModalViewControllerAnimated:YES];
[VC1 performSelector:#selector(showMailModalView) withObject:nil afterDelay:0.2];
I get a EXC_BAD_ACCESS on VC1 because, apparently, my weak reference to VC1 has already been dealloc'd even though VC1 has strong reference to VC2!?!
So my question is...how should this be handled? Would the delegate pattern be better? How would that be triggered?
Note: VC1 is quite large and VC2 isn't often needed so I'm trying to keep VC2 as separate as possible from VC1 (including its own NIB).
VC2 has a weak reference to VC1 and the problem arrises when VC2 tries
to dismiss itself and present
MFMailComposeViewController:
What you have is a circular dependency, since VC1 knows about VC2 and then you let VC2 know about VC1. And When you have circular dependencies, you get all sorts of problems.
You should be using the delegate pattern here. When VC1 presents VC2, it should make itself VC2's delegate. When VC2 is done and wants to dismiss itself, it should let the delegate take care of that operation. In other words, the thing that shows VC2 should be the thing that dismisses VC2. VC2 should be implemented in such a way that it shouldn't know what presented it, only that what presented it will be in charge of dismissing it.
Two similar answers I've given recently:
Pop-up modal with UITableView on iPhone
call method in a subclass of UIView
I've run into the same problem and I'm trying to recall how I fixed it.
You might try calling:
[self.parentViewController dismissModalViewControllerAnimated:YES]
Or could you have your showMailModalView method handle dismissing the current modal view controller before showing the mail composer?
I have a navigationController and 3 View controllers. VC1 pushes VC2 and VC2 uses PresentModalViewController to display the 3rd VC
When VC2 uses presentModalViewController to show VC3, is the VC3 actually pushed on the navigationcontroller stack?
viewdidload of VC3 is called only 1st time. My goal is to show VC3 with a new imageView everytime. Where do I add the code to do that? viewdidappear and viewwillappear of VC3 is not fired either
It is my understanding that VC3 will be in the view hierarchy of VC2 and not the navigationController. In order to be added to the view hierarchy of the navigationController you would have to push VC3 onto it.
viewDidLoad should only be called once, unless the nib file itself was unloaded from memory, due to low memory. The documentation states that viewWillAppear and viewDidAppear should be called on VC3, so I don't know why they are not.
Update
I just tested and VC3 does have -(void)viewDidAppear:(BOOL)animated called. Make sure that the signature on the selector is correct