Is there any way that could send the value in Class of ViewController to Class of View?
Because I want to make a drawing board and I made a modal scene to set values about color, width .
I know how to send the value in modal scene to my ViewController , but now I need use those value in Class of View , or not Class of ViewController.
Sounds like you need to devise a protocol to open a delegation channel between the two classes. Then when the modal VC wants to send data to its delegate (its presenter, in this case), it can of its own volition.
The View Controller can have a reference to the View, therefore the View Controller can simply pass the values to View by calling a View's method or updating View's properties. This is a common pattern: View defines a Protocol and data/requests from View to ViewController go through this Protocol (the ViewController acts as delegate of View); and ViewController owns the View.
For inspiration on how to implement a farily decoupled design applying this pattern, you can have a look at documentation on UICollectionView and UICollectionViewController.
Other options, depending on what design you need, are Key-Value Observing or Notifications.
Related
Lets say I have 2 classes.
One is the well known ViewController (that is set to be the custom class of the first scene in the Interface Builder).
And another class, lets call it B, that I created to draw something inside another view that is a sub view of the main view.
Since I have to get notified whenever some values changes in the sub view in order to do some things in the view controller, I decided to use the delegate pattern.
So I set up the protocol in the B class, but now I have to link the delegate to the view controller class. How can I manage to get the view controller class from the class B?
By the way I instantiate some things using override function willMove(toSuperview newSuperview: UIView?) in B. Can I maybe use newSuperView to get the view controller?
I know it is not the best approach since it may break the MVC Pattern, but I don't know which better way to do this.
To get an idea of what I mean you can look at the image.
My app header is currently a full width, 65pt height UIView which I then use as a generic header for all pages.
class AppHeader: UIView {
...
}
Then, in my Main.storyboard I have a UIViewController with a View from the object library which has its class specified as AppHeader.
My AppHeader (UIView) has multiple buttons which should, if clicked, take you to from the page/controller you're currently on to another.
From the AppHeader class I do not have access to use the present method to show another controller as its not within scope.
Here is my AppHeader.xib:
How can I resolve this?
This is very bad behaviour, you should not use a UIView as a header. You should add a Navigation View Controller as the first view controller of your app. Navigation view controller has the navigation bar where you can put the buttons you want there. From that ones, you will be able to push or present other view controllers.
Check the official documentation: https://developer.apple.com/library/content/documentation/WindowsViews/Conceptual/ViewControllerCatalog/Chapters/NavigationControllers.html
Make your AppHeader view a custom subclass of UIView if it isn't already. Wire the actions on the button to IBAction methods in the view.
Create a protocol AppHeaderDelegateProtocol. Give your AppHeader class a weak delegate property. Define methods in that protocol that let the AppHeader notify it's owning view controller about button presses.
Implement your AppHeaderDelegateProtocol in view controllers that will contain instances of AppHeader.
Connect the delegate property to each instance of AppHeader's owning view controller.
That should do it.
You can create a protocol - call it AppHeaderDelegate or something - and set up your other viewControllers to adopt that protocol. You could define functions to let your delegate know that a certain button was pressed, and your delegate viewController can react to that by presenting the correct view controller.
Apple's docs on protocols here.
Alternatively, you can use NotificationCenter to broadcast notifications to let subscribers know that a certain button was pressed, and have your viewControllers listening for these notifications and reacting to them accordingly. You have to manage when classes start/stop listening, though, as you may have several objects trying to react to a single notification.
I have a UIView which I am using as a seperate module and can include it anywhere I want to. Now I want to navigate to a UIViewController on click of the button inside the UIView.
Hope this is pretty clear.
Short answer: You shouldn't. You need to read up on the MVC design pattern. A UIView is a view object. You are trying to add controller behavior to a view object.
You should take a look at parent/child view controllers, container views, and embed segues. You could easily create a view controller that manages a "tile" inside another view controller, and sends messages to it's parent when the user taps buttons. This is a very common way of doing things.
The best way to do this is to supply the ViewController to the view as a delegate, conforming to a protocol you create for it.
For instance, if you UIView is used to pick an image, then the delegate should have a method akin to:
(void)view:(UIView*)view choseImage:(UIImage*)image;
I have a UIImageView subclass (in swift) set up so I can access touchesBegan/touchesMoved/touchesEnded.
When one of these methods is called, I need to change a property of a different, loaded view.
It seems to me that I will now need to access the active view controller in order to set the properties of this other view. Is there are better way to go about this (such as event methods called in the view controller)?
Note that I'm new to iOS and I am not extremely familiar with the event system yet, as most information I've found is written in Objective C and not in Swift. (Don't worry, I'm looking through Apple's Documentation.)
Also, no, I can't change the UIImageView to a UIButton. Even if I changed to a UIButton, I need access to the individual touchesBegan, etc. methods and the same problem would persist.
If I'm understanding you correctly, you need to reference the UIViewController from the UIImageVIew to push/present a new UIViewController. You have a few options:
Fire an NSNotification from the image view and have an event listener on the view controller.
Create a delegate on the image view that fires a selector on the view controller.
Hold a reference to the view controller on the image view, and push a new view controller from the image view with that reference.
Modally present a new view controller on the application window's rootViewController.
I have a UITableviewController and I push another UIViewController in 'didSelectRow..' method.
I have user input controls (combobox, stepper) in this viewController, that when the UIViewController is popped , I would like to receive the newly entered data in the UITableviewController (and update the tableview accordingly).
I saw some questions/answers, and some said to use "Delegation/Protocol" approach, but did not find any specific example how to achieve this.
Can someone help?
Create a new file for your project and choose the Protocol file type. (We'll call it CallBackProtocol.) In the view controller that you push, create a property that has a type of id<CallBackProtocol> delegate;. Have your table controller adopt the protocol and, when it creates the view controller, set controller.delegate = self;.
Define a method in the protocol that lets you pass whatever data you need back to the caller. Implement that method in the table controller and call it from the second view controller just before popping it.
(Or use a NSNotification.)