I have seen everywhere that delegate variable is always set to self.
thirdClass.delegate = self
So i want something like
thirdViewController.delegate = firstViewControllerToDo
In my case,
let thirdClassVar = thirdClass()
thirdClassVar.namVar = "somnam"
thirdClassVar.delegate = firstViewControllerToDo
self.performSegueWithIdentifier("gtoFirstViewcontroller", sender: self)
When i click on button in second screen, it wil return back to first screen but in background I want to do some calculation in thirdClass and after completion of that, it shud display a message in first screen.
How can i achieve this or is there any other way of getting this done.
You want doing something but you do something with wrong way. I think you can do this process with UIButton and IBAction functions, change your algorith for this process.
Related
I'm very new to Swift, and trying to create an app where Swiping between pages works normally but also involves a change in background color based on swipe distance.
Consequently, I want to "hijack" the swipe gesture, so I can add some behavior to it. The best I can find for how to do that is this question/answer.
Translating the code from the chosen answer into Swift 3, I added the following code to my RootViewController's viewDidLoad function:
for subview in (pageViewController?.view.subviews)!{
if let coercedView = subview as? UIScrollView {
coercedView.delegate = (self as! UIScrollViewDelegate)
}
}
My impression was that the above code would let me delegate functions (such as scrollViewDidScroll to the class in which I'm writing the above code, such that I can define that function, call super.scrollViewDidScroll, and then add any other functionality I want.
Unfortunately, the above code, which doesn't throw any compilation errors, does throw an error when I try to build the app:
Could not cast value of type 'My_App.RootViewController' (0x102cbf740) to 'UIScrollViewDelegate' (0x1052b2b00).
Moreover, when I try to write override func scrollViewDidScroll in my class, I get a compilation error telling me the function doesn't exist to override, which makes me think even if I got past the error, it wouldn't get called, and this isn't the right way to handle this issue.
I'm sorry this is such a noobish question, but I'm really quite confused about the basic architecture of how to solve this, and whether I understand the given answer correctly, and what's going wrong.
Am I interpreting delegate and that answer correctly?
Am I delegating to the correct object? (Is that the right terminology here?)
Is there a better way to handle this?
Am I coercing/casting improperly? Should I instead do:
view.delegate = (SomeHandMadeViewDelegateWhichDefinesScrollViewDidScroll as! UIScrollViewDelegate)
or something similar/different (another nested casting with let coercedSelf = self as? UIScrollViewDelegate or something?
Thanks!
If I understand your question correctly, you want to catch some scroll position and stuff right ? Then do
class RootViewController {
// Your stuff
for subview in pageViewController!.view.subviews {
if let coercedView = subview as? UIScrollView {
coercedView.delegate = self
}
}
extension RootViewController : UIScrollViewDelegate {
// Your scrollView stuff there
}
I have a progress bar (with its own controller). This bar is supposed to be shown in different views depending on which view is visible. As the progress will be same, If possible I don't want to create many progress bar in many views rather I want to use same instance in all these views. Also in that way when I need to change any property of the progress bar it will be reflected commonly, which is required.
Please suggest me how can I use this common view. And also if my strategy is wrong, what would be the better design for such scenarios.
1) Well you have 2 options. You can declare a new Class ViewBox (or whatever name) and then use that inside your code
First View Controller
var box:ViewBox = ViewBox()
When you segue or transition to your next screen, you can have a predefined variable var box:ViewBox!. Then say when you press a button, the button has a function called transition.
//Now setup the transition inside the Storyboard and name the identifier "toThirdViewController"
override func prepareForSegue(segue:UIStoryboardSegue, sender:AnyObject?) {
if(segue.identifier == "toThirdViewController") {
var vc = segue.destinationViewController as! `nextViewController` //The class of your next viewcontroller goes here
vc.box = self.box
}
//Since The SecondViewController doesn't need ViewBox, we don't need it there.
}
where
nextViewController:UIViewController {
var box:ViewBox!
}
Or you could do a much simpler way and that is to look up a UIPageViewController :)
I've had this working in other variations but something seems to elude me in the change from objective-c to swift as well as moving some of the setup into it's own class.
So i have:
class ViewController: UIViewController, interfaceDelegate, scrollChangeDelegate{
let scrollControl = scrollMethods()
let userinterface = interface()
override func viewDidLoad(){
super.viewDidLoad()
loadMenu("Start")
}
func loadMenu(menuName: String) {
userinterface.delegate = self
userinterface.scrollDelegate = self
userinterface.removeFromSuperview() //no impact
scrollControl.removeFromSuperview() //no impact
userinterface.configureView(menuName)
view.addSubview(scrollControl)
scrollControl.addSubview(userinterface)
}
}
This sets everything up correctly but the problem occurs when I change loadMenu() at runtime. So if the user calls loadMenu("AnotherMenu") it won't change the UIView. It will call the right functions but it won't update the view. Although if I call loadMenu("AnotherMenu") at the start, the correct menu will display. Or if I call loadMenu("Start") and then loadMenu("AnotherMenu") then the menu displayed will be "AnotherMenu". As in:
override func viewDidLoad(){
super.viewDidLoad()
loadMenu("Start")
loadMenu("AnotherMenu")
}
When I list all the subviews each time loadMenu() is called, they look correct. Even during runtime. But the display is not updated. So something isn't getting the word. I've tried disabling Auto Layout after searching for similar issues but didn't see a difference.
Try adding setNeedsDisplay() to loadMenu
Eg
func loadMenu(menuName: String) {
userinterface.delegate = self
userinterface.scrollDelegate = self
userinterface.removeFromSuperview() //no impact
scrollControl.removeFromSuperview() //no impact
userinterface.configureView(menuName)
view.addSubview(scrollControl)
scrollControl.addSubview(userinterface)
view.setNeedsDisplay()
}
setNeedsDisplay() forces the view to reload the user interface.
I didn't want to post the whole UIView class as it is long and I thought unrelated. But Dan was right that he would need to know what was going on in those to figure out the answer. So I created a dummy UIView class to stand in and intended to update the question with that. I then just put a button on the ViewController's UIView. That button was able to act on the view created by the dummy. So the problem was in the other class. Yet it was calling the methods of the ViewController and seemingly worked otherwise. So then the issue must be that its acting on an instanced version? The way the uiview class worked, it uses performSelector(). But in making these methods into their own class, I had just lazily wrote
(ViewController() as NSObjectProtocol).performSelector(selector)
when it should have been
(delegate as! NSObjectProtocol).performSelector(selector)
so that was annoying and I wasted the better part of a day on that. But thanks again for the help.
I am building an app for keeping track of reading assignments for a university course. Each ReadingAssignment has included a Bool value that indicates if the reader has finished reading the assignment. The ReadingAssignments are collected into WeeklyAssignment arrays. I want to have the user be able to touch a label and have a checkmark appear and show the assignment as completed. I would like this touch to also update the .checked property to true so I can persist the data.
So, I am trying to have the gestureRecognizer call the labelTicked() method. This works and prints to the console. However, when I try to pass in the assignment parameter, it compiles, but crashes on the touch with an "unrecognized selector" error. I have read every topic i can find here, and haven't found the solution. They all say ":" signifies a Selector with parameters, but still no go.
Can you see what I am doing wrong?
func configureCheckmark(cell: UITableViewCell, withWeeklyAssignment assignment: WeeklyAssignment) {
let checkLabel = cell.viewWithTag(1002) as! UILabel
checkLabel.userInteractionEnabled = true
let gestureRecognizer = UITapGestureRecognizer(target: self, action: Selector("labelTicked:assignment"))
checkLabel.addGestureRecognizer(gestureRecognizer)
}
#objc func labelTicked(assignment: WeeklyAssignment) {
assignment.toggleCheckmark()
if assignment.checked {
label.text = "✔︎"
} else {
label.text = ""
}
}
I would also love to pass in the UILabel checkLabel so I can update it in the labelTicked() method.
Thanks for your help.
There are two distinct problems here:
The syntax for the selector is wrong; the : doesn't mark the beginning of a parameters part, it merely marks that this function takes parameters at all. So the tap recognizer should be initialized as UITapGestureRecognizer(target: self, action: "labelTicked:"). Easy fix. That is the good news.
The bad news: even with perfect syntax it will not work the way you set it up here. Your tap recognizer cannot pass a WeeklyAssignment object as a parameter. In fact, it cannot pass any custom parameter at all. At least, not like that.
However, you can pass it in the sender (which is usually the view the gesture recognizer is attached to). You can grab it by changing your method to
func labelTicked(sender: AnyObject) {
(note that AnyObject may be declared as a more specific type if you know exactly what to expect.)
Going through the sender, you could now theoretically infer which label it is that has been tapped, which data entity that labels corresponds to, and which state the checked property of that entity is in. I think this would become very convoluted very quickly.
Seemingly straightforward things becoming convoluted is usually a good sign that we should take a step back and look for a better solution.
I'd suggest dropping the whole GestureRecognizer approach at this point, and instead exploit the fact that each cell in a table view already comes with its own "tap recongizing" functionality out of the box: the didSelectRowAtIndexPath: method of the table view's delegate. There, you can easily use the supplied NSIndexPath to retrieve the corresponding model entity from the data source to read and modify its parameters as you see fit. Via cellForRowAtIndexPath: you can then get a reference to the correct cell and change its contents accordingly.
Update for Swift 3:
As the Swift language evolves and using String-based selectors (e.g. "labelTicked:") is now flagged as deprecated, I think it's appropriate to provide a small update to the answer.
Using more modern syntax, you could declare your function like this:
#objc func labelTicked(withSender sender: AnyObject) {
and initialize your gesture recognizer like this, using #selector:
UITapGestureRecognizer(target: self, action: #selector(labelTicked(withSender:)))
The correct selector for that function is labelTicked:. Furthermore, you can use a string directly as a selector. Thus:
let gestureRecognizer = UITapGestureRecognizer(target: self, action: "labelTicked:")
But you can't arrange to pass an arbitrary object along to the method when the recognizer fires. A better way to do this is to create a subclass of UITableViewCell. Let's call it AssignmentCell. Give the subclass an assignment property, and move the labelTicked: method to AssignmentCell.
If you've designed the cell in your storyboard, you can add a tap recognizer to the label right in the storyboard, and wire the recognizer to the cell's labelTicked: method in the storyboard.
In your table view data source's tableView(_:cellForRowAtIndexPath:), after you've dequeued the cell, set its assignment property to the assignment for that row.
I have a UITableViewController in my app with a UIRefreshControl added to it. Sometimes however (I'm not sure how to reproduce this, it happens every now and then), I get some extra whitespace at the top of the table view with the refresh control being offset even below that.
This is what it looks like (idle on the left, being pulled down on the right):
I don't have any clue what could be causing this. In my viewdidload I'm only instantiating the refresh control and calling an update function that sets the attributed title. I've moved adding the refresh control to the table view into the viewDidAppear as I've read elsewhere. This is what that code looks like:
override func viewDidLoad() {
super.viewDidLoad()
self.refreshControl = UIRefreshControl()
updateData()
}
override func viewDidAppear(animated: Bool) {
refreshControl!.addTarget(self, action: "updateData", forControlEvents: UIControlEvents.ValueChanged)
tableView.insertSubview(self.refreshControl!, atIndex: 0)
}
func updateData() {
//...
ServerController.sendParkinglotDataRequest() {
(sections, plotList, updateError) in
//...
// Reload the tableView on the main thread, otherwise it will only update once the user interacts with it
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.tableView.reloadData()
// Update the displayed "Last update: " time in the UIRefreshControl
let formatter = NSDateFormatter()
formatter.dateFormat = "dd.MM. HH:mm"
let updateString = NSLocalizedString("LAST_UPDATE", comment: "Last update:")
let title = "\(updateString) \(formatter.stringFromDate(NSDate()))"
let attributedTitle = NSAttributedString(string: title, attributes: nil)
self.refreshControl!.attributedTitle = attributedTitle
})
}
}
Do you need to add the refresh control as a subview of the tableView? I think all you need to do is assign self.refreshControl. According to the documentation:
The default value of this property is nil.
Assigning a refresh control to this property adds the control to the
view controller’s associated interface. You do not need to set the
frame of the refresh control before associating it with the view
controller. The view controller updates the control’s height and width
and sets its position appropriately.
Adding a subview in viewDidAppear could get executed more than once. If you push a controller from a cell and pop back this will get called again. It could be that insertSubview checks if the refresh already has a parent and removes it first, so might not be your issue. You should only do the insert when the controller appears for the first time.
updateData could also be getting added multiple times.
So I think you only need to assign self.refreshControl and then add a handler for the refresh action as you do now using addTarget but this time do it on self.refreshControl.
You can also do all this from storyboard. In storyboard you select the UITableViewController and on the attribute inspector simply set the Refreshing attribute to enabled. This adds a UIRefreshControl into the table and you can see it on the view hierarchy. You can then simply CTRL drag as normal from the refresh control into the .h file and add an action for valueChange which will be fired when you pull down on the refresh control in the table.
Well, I believe that your described behavior might not necessarily be caused by the refresh control.
According to the fact that you don't have any other subviews below your table view I would recommend you to try to place a "fake"-view below your table view. I usually prefer an empty label with 0 side length.
I had similar issues like yours where my table view insets were broken in some cases. And as soon as I used this "fake" subview the problems disappeared. I've read about this issue in some other threads, too. And the solution was this. Seems to be an odd behavior/bug.
Give it a try :)