Schedule-Background-Task-New

This is an example on how to upload images in Background on iOS 13 using a framework called BackgroundTasks

About the Project:

I added ten high quality images (from 1 MB to 3 MB) in the Assets Folder. You can find them at Unsplash

When you open the application for the first time, it will save ten images in the documents folder along with the names of the images locally on Realm

When the background task finishes, it will upload each to the Firebase storage and then delete it from Realm and the documents folder.

You can check if the upload has finished by watching the counter on the main screen, changing to 0 when the upload is done. Also, you can check the firebase storage to see if there is any uploaded image

Using the Demo project:

• First change the Bundle ID to an unique id
• Create a new Firebase Project and use the Bundle ID you created in the first step
• Change the Firebase Storage Rule to the following:

service firebase.storage { match /b/{bucket}/o { match /{allPaths=**} { allow read, write; } } }

NOTE: This is for testing purposes only and this rule should not be used in production!

• Download and move GoogleService-Info.plist to the project, this file can be found on Firebase
• You need to have Cocoapods installed before continuing
• Open Terminal
• Drill down to the project on terminal. One easy way to do this is by typing cd and then dragging the folder to the terminal window
• Once you have drilled down to your project, type pod install and press enter. This will install the required libraries.

For more explanation check the following files BackgroundTaskService.swift and AppDelegate.swift and SceneDelegate.swift

You are probably wondering what is SceneDelegate? This is new on iOS 13. The only thing you need to know for the time being, is that you need to call background task request when the app moves to Background in the function sceneDidEnterBackground inside the file SceneDelegate.swift

What should you do if your project doesn't have SceneDelegate.swift ? You need to open AppDelegate and add applicationDidEnterBackground and inside it call BackgroundTaskService.shared.enterBackground()

Here are steps for debugging, if the background task doesn't trigger immediately.

Apple said you can debug the Background task by doing this steps

• Connect you device to your Mac
• Open the Xcode project and run the project
• Return to Home Screen. This will let you enter into background mode
• Go back to your project
• Click on the Pause button (this button you will found it above debug logs)
• Now enter this line:

e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateLaunchForTaskWithIdentifier:@"com.basil.imagesuploud"]

Have in mind that my background task identifier is com.basil.imagesuploud You need to change the identifier in the info.plist file for your project to match the bundle id. For my demo project you don't need to change anything

After you write that line and click enter, Xcode will say

2019-10-19 17:00:14.615646+0300 Schedule Background Task New[48148:1564536] Simulating launch for task with identifier com.basil.imagesuploud

Now click on the Play button (this button you will found it above debug logs)

Now the background will start immediately. You will see if it works or not

Go back to the application and you will see it change to 0 and when you check the Firebase Storage you will find all the images there

One last thing is to debug if the system kills or stops the background task

same steps as above but only change the command to

e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateExpirationForTaskWithIdentifier:@"com.basil.imagesuploud"]

The excellent example of debugging it, you can test it if you do the above code and after that do the below code on short time. You will notice the task stop before uploading all images: that means it is working fine!

Resources

• https://developer.apple.com/videos/play/wwdc2019/707/
• https://developer.apple.com/documentation/backgroundtasks
• https://medium.com/snowdog-labs/managing-background-tasks-with-new-task-scheduler-in-ios-13-aaabdac0d95b