Context: I have two functions inside my controller that both present a UIImagePickerController with delegate=self
I should do different actions with the image received based on which method spawned de picker
In android I can set a requestCode that behaves like a unique request identifier so when the result comes in delegate function (in this case func imagePickerController) i can differentiate it and i know what to do with it
I don't seem to find anything to differentiate inside delegate function "imagePickerController" so I know which picker caused to method to be called
You can simply add a variable in your self.
var currentPickerId : Int?
Then when you set the delegate:
picker.delegate = self
currentPickerId = 1
And in your delegate method:
switch currentPickerId {
case 1: // Do whatever you want
case 2: // And so on
default: break
}
// And don't forget to reinit the id, you never know... ;p
currentPickerId = nil
Related
I'm trying to keep a timer running even if I switch view controllers. I played around with the Singleton architecture, but I don't quite get it. Pushing a new view controller seems a little easier, but when I call the below method, the view controller that is pushed is blank (doesn't look like the view controller that I created in Storyboards). The timer view controller that I'm trying to push is also the second view controller, if that changes anything.
#objc func timerPressed() {
let timerVC = TimerViewController()
navigationController?.pushViewController(timerVC, animated: true)
}
You need to load it from storyboard
let vc = self.storyboard!.instantiateViewController(withIdentifier: "VCName") as! TimerViewController
self.navigationController?.pushViewController(timerVC, animated: true)
Not sure if your problem is that your controller is blank or that the timer resets. Anyway, in case that you want to keep the time in the memory and not deallocate upon navigating somewhere else I recommend you this.
Create some kind of Constants class which will have a shared param inside.
It could look like this:
class AppConstants {
static let shared = AppConstants()
var timer: Timer?
}
And do whatever you were doing with the timer here accessing it via the shared param.
AppConstants.shared.timer ...
There are different parts to your question. Sh_Khan told you what was wrong with the way you were loading your view controller (simply invoking a view controller’s init method does not load it’s view hierarchy. Typically you will define your view controller’s views in a storyboard, so you need to instantiate it from that storyboard.)
That doesn’t answer the question of how to manage a timer however. A singleton is a good way to go if you want your timer to be global instead of being tied to a particular view controller.
Post the code that you used to create your singleton and we can help you with that.
Edit: Updated to give the TimeManager a delegate:
The idea is pretty simple. Something like this:
protocol TimeManagerDelegate {
func timerDidFire()
}
class TimerManager {
static let sharedTimerManager = TimerManager()
weak var delegate: TimeManagerDelegate?
//methods/vars to manage a shared timer.
func handleTimer(timer: Timer) {
//Put your housekeeping code to manage the timer here
//Now tell our delegate (if any) that the timer has updated.
//Note the "optional chaining" syntax with the `?`. That means that
//If `delegate` == nil, it doesn't do anything.
delegate?.timerDidFire() //Send a message to the delegate, if there is one.
}
}
And then in your view controller:
//Declare that the view controller conforms to the TimeManagerDelegate protocol
class SomeViewController: UIViewController, TimeManagerDelegate {
//This is the function that gets called on the current delegate
func timerDidFire() {
//Update my clock label (or whatever I need to do in response to a timer update.)
}
override func viewWillAppear() {
super.viewWillAppear()
//Since this view controller is appearing, make it the TimeManager's delegate.
sharedTimerManager.delegate = self
}
I have a view named AppPurchaseViewController that calls a function from the IAPManagerm class. After my receipt is validated as a in app purchase, I want to perform a segue using the segue id that I set up in my AppPurchaseViewController class. When I try that, Xcode gives me an error that says "AppPurchaseViewController: 0x117e70ae0>) has no segue with identifier". My code is below
case .purchased:
print("Purchased")
self.validateReceipt(completion: {(success) in
if success {
SKPaymentQueue.default().finishTransaction(transaction)
}
else {
}
//here is where I want to perform the segue
AppPurchaseViewController().performSegue(withIdentifier:'open', sender:nil)
})
Can someone point me in the right direction to get this view to load?
At the top of your IAPManager class, you should declare an instance of type AppPurchaseViewController, like so:
var appPurchaseVC: AppPurchaseViewController!
Whenever you declare your IAPManager, assuming it is from within the AppPurchaseViewController class, you should set the IAPManager’s appPurchaseVC value.
var iapManager = IAPManager()
iapManager.appPurchaseVC = self
Then from within your IAPManager, at a later time when you want to perform the segue, call:
appPurchaseVC.performSegue(withIdentifier:'open', sender:nil)
This ensures that you are calling performSegue from the storyboard instance of AppPurchaseViewController. In your current code, you are creating a new instance of AppPurchaseViewController (I.e., not the one in your storyboard) and then calling performSegue. Because this new instance isn’t in our storyboard, it naturally cannot perform a segue to another view controller in the storyboard.
I feel like I'm missing something and this should not be too hard.
I'm reading in some data in the initial scene in my app.
I've got a singleton and I make the call in viewDidLoad to singleton.getData().
This initial scene is part of a tab controller. And while I thought viewDidLoad would only get called once for each scene I'm pretty sure it's being called a few times during the lifecycle of my app.
So just wondering if there is a way to ensure a function call to retrieve some data only happens once.
viewDidLoad will be called when selected tab is changed, you can change the place you call getData.
If you want to call getData in viewDidLoad and be sure it won't be called multiple times you can create a flag and check, if it is previously called or not.
class Singleton {
static let sharedInstance = Singleton()
private static var getDataCalled = false
func getData() {
if Singleton.getDataCalled {
return
}
Singleton.getDataCalled = true
// request data
print("data requested")
}
}
Singleton.sharedInstance.getData()
Singleton.sharedInstance.getData()
Calling getData multiple times print data requested only once.
I am a newbie to iOS app development trying to build a tip calculator. The basic functioning of the app is completed. My Mainstoryboard has a segment control which shows three % values such as 10, 20, 30. There is a Settings button which on click takes me to a new page and shows the similar % values in a segment control.
What I want to do is that, when a number is clicked (a segment) it should be saved as the default tip% value. How should I pass this value to the Mainstoryboard function where I have written a function to calculate the tip amount?
I suppose you are using a segue for moving to the other view, so use prepareForSegue method:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "tipSegue"
{
if let destinationVC = segue.destinationViewController as? OtherViewController {
destinationVC.tipPercent = someValue
}
}
}
You can write a protocol for setting the default percentage, and have your MainViewController conform to that protocol. When a user taps a button in your SettingsViewController you can call a function (defined within the protocol) to let the "delegate" (MainViewController) know what has happened, and set your default variable accordingly. If this is a permanent setting it might be better to use UserDefaults, as this is exactly what that was designed for. Then, upon loading MainViewController you can access that UserDefaults variable, if it exists.
A little protocol help:
Your protocol could be defined very simply - something like this (and this has to be declared outside of your viewControllers - I often do it above the class declaration of a related viewController):
protocol SettingsDelegate {
func didUpdateDefaultTipPercent(to percent: Float)
}
That's it for the protocol declaration, unless you anticipate needing other functions. Note that you don't actually define the functionality of that function - each viewController that conforms to the protocol may have a different definition of that.
Then, in your settingsViewController you might have an optional variable for protocol conformer like this:
weak var settingsDelegate: SettingsDelegate?
and after the user chooses a default percentage you can safely check to see if the delegate exists and pass that new number to the delegate like so:
if let delegate = self.settingsDelegate {
delegate.didUpdateDefaultTipPercent(to: 15.0) //this "15.0" will come from your segmented control action or whatever
}
In your MainViewController, in your prepareFor(segue... you will need to check to see if you are going to settings, and set Main as the delegate:
...
if let settings = segue.destination as? SettingsViewController {
settings.settingsDelegate = self
}
And, finally, you'll need to make your MainViewController conform to the protocol. I usually do this as an extension just to make it easier to find, and to keep it separated from other things:
extension MainViewController: SettingsDelegate {
func didUpdateDefaultTipPercent(to percent: Float) {
self.defaultPercentage = percent
}
}
When I go to a viewController I call within my viewDidAppear Method a function:
override func viewDidAppear(animated: Bool) {
getLessons()
}
This methods loads from parse.com a list of data I want to use in a pickerView.
The function itself:
func getLessons(){
var query = PFQuery(className:"Lesson")
query.orderByAscending("name")
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
for object in objects {
var name = object["name"] as String
self.languagePickerKeys.append(object.objectId)
self.languagePickerValues.append(name)
self.selectedLanguage.text = self.languagePickerValues.first // set the first lessons name into the text field
self.selectedLessonObjectId = self.languagePickerKeys.first // set the first objectId for the lesson
self.languagePicker?.reloadAllComponents()
}
} else {
// Log details of the failure
println("\(error.userInfo)")
}
}
println("getLessons done")
}
The thing is, that the textfield is empty, as the getLesson() gets the data async and the data is not available to the textfield.
I also tried to put the getLesson into the viewDidAppear method, but this doesn't help me, the textfield is empty anyway.
What can I do, to have the data from the getLessons() method ready and loaded its first value into my textfield when the view is shown to the user?
You certainly have to get the data from asyncTask before setting it to pickerView.
Here's the ViewController lifecycle after instantiation:
Preparation if being segued to.
Outlet setting
Appearing and Disappearing.
So, you have two options:
Load the data in previous ViewController and then perform the segue. You need to follow these steps for it.
a. Create a segue from previous ViewController to your ViewController.
b. Call the function when you want to go next ViewController which fetches the data, and the end (after getting the data) call performSegueWithIdentifier which will lead to your ViewController.
c. Set the data in prepareForSegue
let navigationController = segue.destinationViewController as UINavigationController
navigationController.data = yourData //you got from async call
Now when you reach your ViewController, you are sure that your data is present, and you can set it to your pickerView.
If you want to do it in the same ViewController: here's is the lifeCycle of ViewController:so you need to call your function in viewDidLoad, and always set your pickerView after completion of the async network call.
Make sure that you initiate all changes to the UI from the main thread e.g. like so:
dispatch_async(dispatch_get_main_queue(), {
selectedLanguage.text = languagePickerValues.first
self.languagePicker?.reloadAllComponents()
})
The problem is that findObjectsInBackgroundWithBlock is an asynchronous method, so even if you fire it in the ViewDidLoad you will never know when you will receive the response data and you can't be sure that the data will be ready by the time you view appear.
I think you have just 2 possibility:
The first one is to load the data in the previous view controller and then just pass the data that got ready to you view controller.
The second is to use a synchronous method (the findobject method maybe?) and put the call in a method that is fired BEFORE the view appear (like the viewWillAppear: method). But your view will stuck for a moment (I think) while the data is retreiving... However this second solution probably resolve your problem but using synchronous method to retrieve data from a slower data source is usually bad design solution.
D.