In my app i have several "Managers" objects that handle stuff for me, for example:
FacebookManager - handle all the Facebook methods of my app
ApiManager - handle all our product API connection method
etc..
All those managers should be initialise at when the app starts and terminated once the app is terminated.
Naturally because the AppDelegate handle the start and end of my application i thought to put those instances there, so all other's app's part will have a way of getting them as needed.
Is it a good practice or should i use the app delegate to assign a single-tone in a static variable for each of the managers ?
Related
While working in an iOS app, I found two ways to detect protected data available incident. One using callbacks and other using notifications. I need to know if they provide exact same functionalities or not. From the documentation I am unable to differentiate. So,
What are the differences between,
- (void) applicationProtectedDataDidBecomeAvailable:(UIApplication *)application {}
callback and
UIApplicationProtectedDataDidBecomeAvailable
notification?
applicationProtectedDataDidBecomeAvailable - On a device that uses content protection, protected files are stored in an encrypted form and made available only at certain times, usually when the device is unlocked. This notification lets your app know that the device is now unlocked and that you may access certain types of protected files again.
UIApplicationProtectedDataDidBecomeAvailable - Posted when the protected files become available for your code to access.
They provide the identical functionalities.
applicationProtectedDataDidBecomeAvailable is a UIApplicationDelegate method, and UIApplicationProtectedDataDidBecomeAvailable is a NSNotification Name.
An analogy is applicationDidBecomeActive: and UIApplicationDidBecomeActiveNotification, the former is a delegate method will be called when become active, meanwhile the latter will be post.
I tested:
UIControl().sendAction(#selector(URLSessionTask.suspend), to: UIApplication.shared, for: nil)
which is for putting app on background and it works.
How do I put app back on foreground?
I tried:
UIControl().sendAction(#selector(URLSessionTask.resume), to: UIApplication.shared, for: nil)
But eventually it crashes...
Thank you
Update:
Since you've indicated that you're looking for any technical solution, even those not compatible with the App Store or Apple's terms, this should be possible using the Private API LSApplicationWorkspace: openApplicationWithBundleID. Try something like this:
Create a .h file and set up an interface to the LSApplicationWorkspace class and list the required method. You will need to #import "PrivateHeaders.h" in your bridging header.
//
// PrivateHeaders.h
//
#ifndef PrivateHeaders_h
#define PrivateHeaders_h
#interface LSApplicationWorkspace : NSObject
- (bool)openApplicationWithBundleID:(id)arg1;
#end
#endif /* PrivateHeaders_h */
You should then be able to call this function and pass in the Bundle Identifier of your app as an string.
//
// SomeClass.swift
//
import MobileCoreServices
let workspace = LSApplicationWorkspace()
/**
Launch an App given its bundle identifier
- parameter bundleIdentifier: The bundle identifier of the app to launch
- returns: True if app is launched, otherwise false
*/
func openApp(withBundleIdentifier bundleIdentifier: String) -> Bool {
// Call the Private API LSApplicationWorkspace method
return workspace.openApplication(withBundleID: bundleIdentifier)
}
Original:
What you are doing is likely a violation of the iOS Human Interface Guidelines (although the "Don’t Quit Programmatically" is no longer specifically defined), so as the comments have said, it is not suited to the App Store. Regardless, once your app is suspended in this way, I don't expect that there is a way to resume it programmatically, unless you can hook into a Background Operation to run URLSessionTask.resume, but I have not tested it and am unsure whether it can work.
Apps can be launched (and hence brought into the foreground) programmatically from another app or today extension by using a Custom URL Scheme, or via a Push Notification. It isn't possible to launch the app from the Background Operation via a URL Scheme, since it is part of the UIKit framework, which must be run in the main thread.
In summary, I think your best option is to try to use a Notification. This just means that the user will need to click on the notification to bring your app back into the foreground.
Closing/opening the app should be done explicitly by the user. Any other way of closing or opening the app is not supported by Apple and will be rejected when uploaded to app store. iOS Human Interface Guideline states:
Don’t Quit Programmatically
Never quit an iOS application
programmatically because people tend to interpret this as a crash.
However, if external circumstances prevent your application from
functioning as intended, you need to tell your users about the
situation and explain what they can do about it. Depending on how
severe the application malfunction is, you have two choices.
*Display
an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures usersthat
there’s nothing wrong with your application. It puts usersin control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
*If only some of your application's features are
not working, display either a screen or an alert when people activate
the feature. Display the alert only when people try to accessthe
feature that isn’t functioning
Just as a follow up to Jordan's excellent answer I want to give an explanation for why your code works in the first place and why that alone will get your app rejected, even without any functionality to make it active again and bring it to the foreground.
As maddy pointed out in a comment, you're basically calling a method from UIApplication's private API. This works due to the Objective-C runtime's dynamic linking. You might wonder "But I am using Swift, what does that have to do with Objective-C?" The answer lies in #selector mechanism. A Selector is basically just a symbol that the Objective-C runtime looks up in a table to get a method it invokes (for you). This is why it's technically not correct to say you "call a method" when you do something like myObjectInstance.someMethod(). The correct way to phrase that would be to "send a message" to the object, because that's what is happening in the runtime. The target-action mechanism is build around that. The sendAction(_: Selector?, to: Any?) method does the same thing. So in effect your code does the following:
Get the symbol that corresponds to URLSessionTask's suspend() method.
Tell the shared instance of UIApplication to invoke the method that it has for that symbol.
Now usually that would result in a crash with the typical "unknown selector sent to instance..." error message. But here, by sure coincidence UIApplication also has a method for that instance (or rather, the runtime also has one of its methods listed in its table for that symbol). You kind of "found" a method that is not declared in its public header. You successfully circumvented a compile-time check for this and invoke a method that is part of a private API. This is explicitly forbidden in the Apple Developer Program License Agreement
Besides all that, I would strongly advise against trying to design an app that way in the first place. As maddy pointed out it's also likely considered to violate the HIGs. Even if you're not trying to do anything malicious and properly explain the feature in your app's description, that won't make Apple let it slide (I assume). Personally, as a user, I'd also find it annoying if the app did something the system already has a specific mechanic for in a different manner, at least in terms of app's coming to background and foreground.
I don't think it can be done without user interaction
The option is you can generate a push notification to tell the user to bring the application to foreground
When the operating system delivers push notification and the target application is not running in the foreground, it presents the notification.
If there is a notification alert and the user taps or clicks the action button (or moves the action slider), the application launches and calls a method to pass in the local-notification object or remote-notification payload.
I tested:
UIControl().sendAction(#selector(URLSessionTask.suspend), to: UIApplication.shared, for: nil)
which is for putting app on background and it works.
How do I put app back on foreground?
I tried:
UIControl().sendAction(#selector(URLSessionTask.resume), to: UIApplication.shared, for: nil)
But eventually it crashes...
Thank you
Update:
Since you've indicated that you're looking for any technical solution, even those not compatible with the App Store or Apple's terms, this should be possible using the Private API LSApplicationWorkspace: openApplicationWithBundleID. Try something like this:
Create a .h file and set up an interface to the LSApplicationWorkspace class and list the required method. You will need to #import "PrivateHeaders.h" in your bridging header.
//
// PrivateHeaders.h
//
#ifndef PrivateHeaders_h
#define PrivateHeaders_h
#interface LSApplicationWorkspace : NSObject
- (bool)openApplicationWithBundleID:(id)arg1;
#end
#endif /* PrivateHeaders_h */
You should then be able to call this function and pass in the Bundle Identifier of your app as an string.
//
// SomeClass.swift
//
import MobileCoreServices
let workspace = LSApplicationWorkspace()
/**
Launch an App given its bundle identifier
- parameter bundleIdentifier: The bundle identifier of the app to launch
- returns: True if app is launched, otherwise false
*/
func openApp(withBundleIdentifier bundleIdentifier: String) -> Bool {
// Call the Private API LSApplicationWorkspace method
return workspace.openApplication(withBundleID: bundleIdentifier)
}
Original:
What you are doing is likely a violation of the iOS Human Interface Guidelines (although the "Don’t Quit Programmatically" is no longer specifically defined), so as the comments have said, it is not suited to the App Store. Regardless, once your app is suspended in this way, I don't expect that there is a way to resume it programmatically, unless you can hook into a Background Operation to run URLSessionTask.resume, but I have not tested it and am unsure whether it can work.
Apps can be launched (and hence brought into the foreground) programmatically from another app or today extension by using a Custom URL Scheme, or via a Push Notification. It isn't possible to launch the app from the Background Operation via a URL Scheme, since it is part of the UIKit framework, which must be run in the main thread.
In summary, I think your best option is to try to use a Notification. This just means that the user will need to click on the notification to bring your app back into the foreground.
Closing/opening the app should be done explicitly by the user. Any other way of closing or opening the app is not supported by Apple and will be rejected when uploaded to app store. iOS Human Interface Guideline states:
Don’t Quit Programmatically
Never quit an iOS application
programmatically because people tend to interpret this as a crash.
However, if external circumstances prevent your application from
functioning as intended, you need to tell your users about the
situation and explain what they can do about it. Depending on how
severe the application malfunction is, you have two choices.
*Display
an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures usersthat
there’s nothing wrong with your application. It puts usersin control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
*If only some of your application's features are
not working, display either a screen or an alert when people activate
the feature. Display the alert only when people try to accessthe
feature that isn’t functioning
Just as a follow up to Jordan's excellent answer I want to give an explanation for why your code works in the first place and why that alone will get your app rejected, even without any functionality to make it active again and bring it to the foreground.
As maddy pointed out in a comment, you're basically calling a method from UIApplication's private API. This works due to the Objective-C runtime's dynamic linking. You might wonder "But I am using Swift, what does that have to do with Objective-C?" The answer lies in #selector mechanism. A Selector is basically just a symbol that the Objective-C runtime looks up in a table to get a method it invokes (for you). This is why it's technically not correct to say you "call a method" when you do something like myObjectInstance.someMethod(). The correct way to phrase that would be to "send a message" to the object, because that's what is happening in the runtime. The target-action mechanism is build around that. The sendAction(_: Selector?, to: Any?) method does the same thing. So in effect your code does the following:
Get the symbol that corresponds to URLSessionTask's suspend() method.
Tell the shared instance of UIApplication to invoke the method that it has for that symbol.
Now usually that would result in a crash with the typical "unknown selector sent to instance..." error message. But here, by sure coincidence UIApplication also has a method for that instance (or rather, the runtime also has one of its methods listed in its table for that symbol). You kind of "found" a method that is not declared in its public header. You successfully circumvented a compile-time check for this and invoke a method that is part of a private API. This is explicitly forbidden in the Apple Developer Program License Agreement
Besides all that, I would strongly advise against trying to design an app that way in the first place. As maddy pointed out it's also likely considered to violate the HIGs. Even if you're not trying to do anything malicious and properly explain the feature in your app's description, that won't make Apple let it slide (I assume). Personally, as a user, I'd also find it annoying if the app did something the system already has a specific mechanic for in a different manner, at least in terms of app's coming to background and foreground.
I don't think it can be done without user interaction
The option is you can generate a push notification to tell the user to bring the application to foreground
When the operating system delivers push notification and the target application is not running in the foreground, it presents the notification.
If there is a notification alert and the user taps or clicks the action button (or moves the action slider), the application launches and calls a method to pass in the local-notification object or remote-notification payload.
I have been working on iOS framework (in Swift) which contains beacon functionality. I made it work except that I'm not sure how to handle scenario where I'm in foreground and I encounter multiple beacons in short duration.
If I want didReceive delegate method to show Alert for beacon while in foreground, and if I encounter many beacons it will not work nicely (alerts will display one over another). Is there some solution to queue notifications somehow?
Also I would like to know, if there is a way to make all that logic for receiving local notifications inside my framework?
I have to be able to support iOS-8.0 so I can't use Notification Center which is available from iOS-10.0
Can I create some class which would act like appdelegate (probably some class which would implement UIApplicationDelegate inside framework), is something like that possible?
I want to put as much code as I can inside framework itself so that it won't be too messy job for someone to include that framework with all functionality.
After some time I figured out a way to make this. I'm beginner in iOS with few months experience so I can't say if this solution is the best but it works for me.
I found a way to implement all push and local notification related delegate methods from framework. Basically if main application wants framework to take care of notifications without having to implement anything yourself, on runtime framework will dynamically implement certain UIApplicationDelegate methods for AppDelegate.swift class (or whatever is your AppDelegate class called).
I used object_getClass(UIApplication.shared.delegate!) to get the main class.
Then I used func class_addMethod(_ cls: AnyClass!, _ name: Selector!, _ imp: IMP!, _ types: UnsafePointer!) -> Bool
to implement delegate methods for push and local notifications from inside framework so now it comes down to write one or two lines to use framework entirely with working notifications and beacon location services instead of having to write a lots of code outside framework.
As for handling notifications in foreground mode I made that work by adding them to queue so that if more than one notification comes, and wants to be displayed in foreground regime, only one will be displayed by UIAlertController and the rest will be put in queue and sent again but with some small delay (I set fire date to be some value which I thought was appropriate in my case) after user makes an action regarding that first notification which was the only one presented.
These are just my ideas for the problems I had, if someone shows interest for these solutions I will write more details if needed. I will also gladly accept any criticism.
This is a question about iOS memory management when app enters the background.
If I have a var in the AppDelegate with a value:
#interface MyAppDelegate : NSObject {
NSString *userName;
}
// In some place
((MyAppDelegate*)[UIApplication sharedApplication] delegate]).userName = #"StackOverflow"
My question is: when the app enters the background, because the user receives a call or opens another app, is it possible that iOS releases the memory for any reason (so destroying my AppDelegate instance)? So I lose the value of userName?
Programming in Android we have to use persistence mechanisms like Parcelable, using methods of lifecycle like onSaveInstance, etc. But in iOS we don't have to manage values of var for the "iOS garbage collection"?
Maybe the answer can be trivial talking about a String var, but what happens when I stored in the AppDelegate a big Array of UIImages? It will never be release when app enter on background?
Sorry for my bad english and I can't find information about lifecycle iOS, appDelegate and memory management.
You never really know. iOS might need to remove the app from memory to use it for something else. If the user closes the app for just a minute then you might be ok, but the app could be closed for days, and the user may do any number of other things...
So, you should really either:
Save data each time it changes, or
Save data when the app is told that it is going to the background
Option 1. is more safe, because it also saves data against crashes, but it isn't always practical. Generally, save as soon as you can and, if testing shows you need to, later work on making things run better (like by processing and saving to disk on a background thread).
When an app is launched, the UIApplicationMain function is called, this function creates a singleton UIApplication object.
When you declare an iVar like this : NSString *userName; you are creating a strong reference to it ( by default it's strong).
To answer your question : the userName will be released when the UIApplication will be released and because the UIApplication is a singleton, it will be never release until the application is not killed. The application will be killed in many situations :
The user kill the app
The system kill the app (memory,...)
Documentation :
Memory management
iOS App life cycle