Authenticate once and share data between multiple application

On your local machine, navigate to your ./<SAP BTP SDK for iOS> folder. Double-click the SAP BTP SDK Assistant for iOS icon to start the application.

Click the Plus button on the top-right of the SAP BTP SDK Assistant for iOS. The first page of the Xcode Project generation wizard lets you define the Project Properties.

Enter the following details:

Click Next to advance to the SAP Mobile Services for development and operations Configuration step.

In the SAP Mobile Services for development and operations Configuration page, select the Sample tab button.

The Sample Application Identifier and Sample Application Name are now pre-filled with the Bundle Identifier value from the previous page.

Click Next to advance to the OData Services step.

In the OData Services page, the Sample OData service connection you have specified in the previous wizard step is displayed:

Click Next to advance to the Optional Features step.

In the Optional Features page, you have the option to generate a Master-Detail Application, enable logging and log uploads, and enable remote notifications. Since you’re using the Sample OData service, all settings are enabled but greyed out.

After you have clicked Finish in the previous step, the SAP BTP SDK Assistant for iOS now loads the OData service’s metadata. This metadata describes the data model, and can be accessed via <service URL>$metadata. For your service, the metadata URL would be https://hcpms-<your account>trial.hanatrial.ondemand.com/SampleServices/ESPM.svc/$metadata

After the SAP BTP SDK Assistant for iOS has finished, Xcode will launch and open the just generated SharedOne project.

In Xcode, open the SharedOne project settings, and switch to the Capabilities tab. Scroll down to the App Groups capability, and set the switch next to it to On.

Click the Plus button below it, and provide the following App Group ID:

Open file SharedOne > Onboarding > OnboardingManager.swift and locate method configuredStoreManagerStep()

Replace the following line:

let step = StoreManagerStep()

with this:

let keychainGroupName: String = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
let uuid:UUID = UUID(uuidString: "ec429dd6-3fd1-4556-b600-bac39ee9f6e7")!

let storeManager = KeychainStoreManager(keychainAccessGroup: keychainGroupName)

let step = StoreManagerStep(persistentStoreManager: storeManager)
step.runRestoreIfStoreExists = true
step.storeID = uuid

With this code, the following is happening:

1. The keychainGroupName variable contains the value specified in the project’s App Groups entitlement. Along with the uuid, these are used to support the shared key store between applications.
2. The KeychainStoreManager is then initialized with the specified keychainGroupName and stored in constant storeManager.
3. The StoreManagerStep is then initialized with the storeManager as the persistent store manager.
4. When using a shared store, you don’t want an error thrown when a store is created which is already been created by a different app. To bypass this behavior of the step, flag runRestoreIfStoreExists should be set to true.
5. In order to share the same store ID, the step’s storeID is set to a hard-coded uuid value.

Repeat steps 1-3, but now, everywhere it says SharedOne, enter or use SharedTwo instead.

Open the Xcode project for the first app SharedOne, and open AppDelegate.swift file.

Add the following method:

func storeData() {
    let storeName      = "MyStore"
    let cipherPassword = "1qaz@WSX"
    let cipherSalt     = "mySalt"
    let keychainGroup  = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
    let key            = "myKey"

    let data = "String saved from SharedOne".data(using: .utf8)

    do {
        let cipher = try Cipher (password: cipherPassword, salt: cipherSalt)
        let keychainStorage = try KeychainStorage.openStore (name: storeName, cipher: cipher, accessGroup: keychainGroup)
        try keychainStorage.put (data: data!, for: key)
    } catch let error {
        self.logger.error("Store opening failed!", error: error)
    }

}

This method opens a store with the provided name and cipher for the predefined keychainGroupName, and stores a Data object data (which holds a simple string encoded using UTF-8) with key myKey.

Next, locate method application(_:didFinishLaunchingWithOptions:) and just above the bottom return statement, add:

storeData()

If you now build and run the app SharedOne, after you have logged in and accepted the EULA, the app should run with the Collections view displaying the available OData entities, just like it normally would. However, since method storeData() has been called, an entry with key myKey is now added to the shared store.

Switch to the Xcode project for the second app SharedTwo, and open AppDelegate.swift file.

Add the following method:

func retrieveData() {
    let storeName      = "MyStore"
    let cipherPassword = "1qaz@WSX"
    let cipherSalt     = "mySalt"
    let keychainGroup  = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
    let key            = "myKey"

    do {
        let cipher = try Cipher (password: cipherPassword, salt: cipherSalt)
        let keychainStorage = try KeychainStorage.openStore (name: storeName, cipher: cipher, accessGroup: keychainGroup)

        let data = try keychainStorage.data(for: key)
        let dataString = String(data: data!, encoding: .utf8)

        logger.info("Data retrieved : \(String(describing: dataString))")
    } catch let error {
        logger.error("Store opening failed!", error: error)
    }

}

Similar to the code used in the first app SharedOne, this method opens a store with the provided name and cipher for the predefined keychainGroupName. But in this case, it now loads a Data object data for key myKey (which is then decoded using UTF-8 into constant dataString).

The decoded content is then printed to the console using the logger.

Next, locate method application(_:didFinishLaunchingWithOptions:) and at the top of that method, add:

logger.logLevel = .info

This ensures the info logging of method retrieveData() will be printed to the console.

Finally, just above the bottom return statement, add:

retrieveData()

If you now build and run the app SharedTwo, after you have logged in and accepted the EULA, the app should run with the Collections view displaying the available OData entities, just like it normally would. However, since method retrieveData() has been called, the entry with key myKey which was stored from SharedOne is now retrieved to the shared store and its content printed to the console:

Now close both running apps, and open one of them again. You now notice you don’t need to logon to both apps anymore, since the credentials are stored in the shared key store.