I'm making an iOS app (first actual app that isn't Hello World), and it will have 2 screens. I asked on here before how to make one screen (or View Controller) open another, and this is what I figured out to use:
[self presentViewController:[[self storyboard] instantiateViewControllerWithIdentifier:#"statView"] animated:YES completion:nil];
It works. However, it gives me the following message when this runs:
Unknown class statView in Interface Builder file.
(Note: this doesn't stop me from using the app, it just seems to be a warning.
This leads me to believe I'm doing something wrong. Also, it seems I'm instantiating this new view controller, but never getting rid of it. So when I go back and forth, I imagine I might be leaving these View Controllers instantiated as new every time?
So my question is:
If there is a better way to switch between these windows, how can it be done?
If this is correct, why the error message?
The most easy way is unsing the Storyboard.
Add a button and link it to the second view.
You can use a Segue to parse data:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([[segue identifier] isEqualToString:#"SEGUENAME"]) {
SecondViewController *secondViewController = [segue destinationViewController];
secondViewController.parameter = parameter; // Parse a value
}
}
Related
I perform a segue which is defined in the Storyboard to open a new view controller. I need to configure the destination view controller of the segue in a special state where some of it's buttons does not needed to be displayed.
I know that I can do this by setting a variable on this controller in my source view controller's -prepareForSegue:sender:. The problem with this is, that firstly it instantiates the controller, so it's -viewDidLoad: will run, then only after can I set anything on it.
I can't create the controller entirely from code, because it's user interface is in Storyboard. -instantiateViewControllerWithIdentifier: also calls -viewDidLoad first obviously.
I could probably use a semaphore and add the initialization code into my destination controller's -viewWillAppear, but that's ugly, it has to be some more elegant way to do this than doing a check every time the view appears. (My settings need to be done only once.)
Is there some way to pass variables into the controller before it's -viewDidLoad runs?
EDIT: It looks like this happens only if I trigger the segue from code using -performSegueWithIdentifier:.
On my machine and on iOS 8.0 and iOS 9.0, viewDidLoad is called after prepareForSegue. So, something like the following worked for my test case of your answer.
In your source controller:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
TimViewController * controller = segue.destinationViewController;
if( [controller isKindOfClass:[TimViewController class]] )
controller.name = #"tim";
}
In your destination controller (TimViewController):
- (void)viewDidLoad
{
[super viewDidLoad];
// Do view setup here.
NSLog( #"view did load %#", self.name );
}
Add a segue (a show segue) from your source control to the destination view controller.
Output:
2015-09-17 19:09:04.351 Test[51471:7984717] view did load tim
I think there is some confusion here. -prepareForSegue:sender: gets called before -viewDidLoad gets called. Please double check your implementation.
Edit:
May be this thread will help you understand this and one of the mentioned cases fall in your case.
hey guys created a custom segue tab bar, using this guys tutorial,
http://www.scott-sherwood.com/tutorial/ios-5-creating-a-custom-side-tabbar-using-storyboards-and-custom-segues/
after trying to figure out why why my app doesn't work, i realised that the technique i was using was about replacing the existing view with the linked ViewController as a subview.
////////////////////////////////////////// the over-written perform method as follows /////////////////////////
-(void) perform {
ViewController *src = (ViewController *)[self sourceViewController];
UIViewController *dst = (UIViewController *) self.destinationViewController;
for (UIView *view in src.placeholderView.subviews ) {
[view removeFromSuperview];
}
src.currentViewController = dst;
[src.placeholderView addSubview:dst.view]; }
////////////////////////////////////////////// /////////////////////// /////////////////////// ///////////////////////
now once i am on the linked ViewControllers i was hoping to add another link to another ViewController which would hold the Editing functions for the information each respective pervious ViewControllers. Now when i try to connect a the ViewControllers via any Segue the app crashes and give me a Thread 1:EXC_BAD_ACCESS. When i use NSZombie its give me this in the console,
[UIStoryboardSegueTemplate performSelector:withObject:withObject:]: message sent to deallocated instance 0x7c3a4d20
no i understand what is happening in theory, the viewController is trying to ad the next one to an empty space (i think the entire placeHolder has been deleted thus giving the viewController nowhere to go) i think, i was wondering if anyone could help with this i mean i a have been looking everywhere for a solution but i keep getting the same error.
i even created a VieController class for the ProfileViewController.m/ProfileViewController.h in which i add
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([[segue identifier] isEqualToString:#"ProfileEditSegue"]){
ProfileViewController *cvc = (ProfileViewController *)[segue destinationViewController];
[cvc.placeholderView addSubview:cvc.view];
}
}
this to leads me to the same errors. I will be glad to send anyone my source files, the same error occurs when i do it on the supplied files from the tutorial.
PS. i am using this method so that i can have a vertical navigation bar, but i want to do it simply so i could also learn how one works and be able to use/develope it further.
any help would be great
The problem wasnt in those methods it was because the currentViewController instances was set to weak instead of strong
i am trying to send the view to next view but when i try to come back to the root page it crashes and say that Navigation Bar subview tree might get corrupted issue
- (IBAction)nxtBtn:(id)sender {
//here i am sending it to next view...
[self performSegueWithIdentifier:#"next" sender:(id)sender];
}
//function for segue
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
//next is the name of the identifier
if ([segue.identifier isEqualToString:#"next"]) {
nextViewController *vc=(nextViewController *)segue.destinationViewController;
vc.str=sender;
}
}
we don't need any kind of identifier for simple use of segue i.e. navigating from one view to another without passing any data. just simple as that you have to connect the segue from one view to other and run the application. it will work properly.
I have a the first application controller, MAViewControllerMenu, and when that controller loads, I already allocate the next controller, imageControllerView.
- (void)viewDidAppear{
[super viewDidAppear:(YES)];
if (!imageControllerView)
imageControllerView = [[self storyboard] instantiateViewControllerWithIdentifier:#"chosenImageController"];
}
Then, I select an image from the image picker, and want to move to the next controller,imageControllerView, where the image would be displayed. I set the next window's image property as follows:
imageControllerView.image = [[self.pageViews objectAtIndex:(centered_image_ind)] image];
This line works, I checked that there's a value in imageControllerView.image.
However, when I move to the next controller,imageControllerView , I notice that the memory address of imageControllerView changes, or in other words, imageControllerView's properties that I change before moving to that controller, specifically image, reset when I move there.
Instead of throwing code here, I was hoping you could let me know what I should provide.
I think it's a common problem people know of:
Controller's objects re-init'ing when moving from one controller to another.
Here's a screen shot that might give a hint of what Im trying to do
Left most one is where I select pictures which in turn go into the slide show scrollview. Then I click next, and the image is supposed to appear in the centered ImageView
Thanks
OK...
You cannot "already allocate the next view controller" this won't work. There is no point in creating it like this at all. You can delete the imageViewController property (or iVar) completely.
The arrows that you have between the view controllers in your storyboard are segues. In Interface Builder you can select a segue and give it an identifier. For instance you would use something like #"ImageViewSegue".
I guess the segue is attached to the Next button. This is fine.
Now, in your MAViewControllerMenu you need to put this method...
- (void)prepareForSegue:(UIStoryBoardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"ImageViewSegue"]) {
// the controller is CREATED by the segue.
// the one you create in view did load is never used
ImageViewController *controller = segue.destinationController;
controller.image = [[self.pageViews objectAtIndex:(centered_image_ind)] image];
}
}
Now for the segues in the other direction...
You appear to be using segues to dismiss the modal views. You can't do this. What it will do is create a new view controller and present that instead of dismissing the presented view.
i.e. you'll go...
A -> B -> C -> B -> A -> B
// you'll now have 6 view controllers in memory
// each segue will create a fresh view controller with no values set.
What you want is...
A -> B -> C
A -> B
A
// now you only have one view controller because the others were dismissed.
// when you dismiss a view controller it will go back to the original one.
// the original one will have all the values you set previously.
To do this you need to create a method something like...
- (IBAction)dismissView
{
[self dismissViewControllerAnimated:YES completion:nil];
}
Then whatever the button is for your dismiss action attach it to this method.
Now delete all the backwards curly segues.
Passing info back
To pass info back to the original view controller you need a delegation pattern or something similar.
You can read more about creating a delegate at This random Google Search
Create a delegate method something like...
- (void)imageViewSelectedImage:(UIImage *)image;
or something like this.
Now when you do prepareForSegue you can do...
controller.delegate = self;
and have a method...
- (void)imageViewSelectedImage:(UIImage *)image
{
// save the method that has been sent back into an array or something
}
I might be wrong, but seems you go to your second view controller using a segue, it is normal your controller instance isn't the same than the one retrieved by [[self storyboard] instantiateViewControllerWithIdentifier:#"chosenImageController"]
you should take a look at - (void) prepareForSegue:(UIStoryboardSegue *)segue
(UIViewController method)
inside this method set your image property to the segue destination controller (check the identifier of the segue)
I know we still can do it by programmation,.. that's what i'm using for now (as iOS 4).
The old way was to init your controller, set property, then Push.
But with iOS 5, since the main storyboard is the "new" way to design your application.
I was wondering if it is any possible way to do the same, setting a property then pushing using the link in your mainstoryboard ?
It is so easy now to push, but not really useful if you want to set a property....
I don't know if I explained it clearly.. but it is really basic stuff.
Anyone?
You'd now use prepareForSegue: method to do any customisation. You can grab a reference to the view you're about to push and manipulate it, similar to this...
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Check we're referring to the right segue
if ([[segue identifier] isEqualToString:#"YOUR_SEGUE_NAME_HERE"])
{
// Get reference to the destination view controller
YourViewController *vc = [segue destinationViewController];
// Do your customisations here
}
}
I just wrote two blog posts on how to do this. You can read it here and it should clarify (with example) how to do it.