How to use Content Hosting for In-App Purchase Content

Apple allows apps developers to host their In-App Purchase Content on Apple’s servers.  To set up Content Hosting you will need to use iTunes Connect, Xcode and the Application Loader.  The IAP must be non-consumable to take advantage of content hosting.

iTunes Connect

Go to your app in iTunes Connect, then select Features, In-App Purchases.  Create a new In-App Purchase or select an existing one.  In the Content Hosting section, press “Turn On Content Hosting”.



You will need to create a new Xcode project to host your In-App Purchase Content.

In Xcode, go to File -> New -> Project….  Then select the Cross-platform tab and the In-App Purchase Content template.  Set your Product Name and Organization Identifier such that the resulting Bundle Identifier matches the Product ID of the IAP in iTunes Connect.

Add your IAP content to the same folder that contains the ContentInfo.plist file.  When your done adding content files, select: Product -> Archive.  From the Organizer, press Export and select “Export as an Installer Package” to create a .pkg file.

Don’t bother validating the project.  If you do you’ll just get the error “An error occurred. Archive item is not associated with any known iTunes Connect platform.”  This is because you need to use the Application Loader and not Xcode Organizer.

In your main iOS app project you’ll have to implement SKPaymentQueue start, cancel, pause, and resumeDownloads functions.  Each of these takes an array of SKDownload objects.  You’ll also want to implement the SKPaymentTransactionObserver func paymentQueue(SKPaymentQueue, updatedDownloads: [SKDownload]).

Note that while the hosted content is downloaded as a zip file you do not need to unzip it.  The files are in the Contents directory.  You can use the sample code below to iterate through the contents directory.  You’ll need to copy the files over to your Application Support Path.  You’ll also need to exclude the files from iCloud backup.  Finally, you can delete the zip file from the cache directory.

func procesessDownload(download: SKDownload) {
    guard let hostedContentPath = download.contentURL?.appendingPathComponent("Contents") else {

    do {
        let files = try FileManager.default.contentsOfDirectory(atPath: hostedContentPath.relativePath)
        for file in files {
            let source = hostedContentPath.appendingPathComponent(file)
            //copy to Application Support Path and mark as exclude from iCloud backup
        //Delete cached file
        do {
            try FileManager.default.removeItem(at: download.contentURL!)
        } catch {
            //catch error
    } catch {
        //catch error


Application Loader

 You’ll need to upload your IAP .pkg content file via the Application Loader program.  If it is your fist time using the Application Loader you’ll need to sign in with your iTunes username and an app specific password. You can create an App Specific Password at!&page=signin and select “Generate Password…”.  If you’ve used Application Loader in the past but haven’t updated it to use an App Specific password you’ll have to sign out and sign back in with the new password.

Select the New In-App purchases template, then Choose.  Now select the corresponding App and press Manage.  Select the IAP you would like to upload the content to.  Update the Name and Review Notes if necessary and select Next until you get to the “Hosted Content” tab.  Press Choose and select the .pkg file from earlier.

Press Next and save the .itmsp file to disk and press Deliver to upload the file to Apple’s servers.

If you get the following error: ERROR-ITMS-2000 “Version x, Locale ”xx-xx’: keywords cannot be edited in the current state” at Software/SoftwareMetadata/SoftwareVersion you’ll have to manually edit your .itmsp file to remove the metadata of the previous version.  See the following Stack Overflow post on the workaround


To test your In-App Purchases in development mode on your test devices you will have to set up a sandbox user in iTunes Connect.  Follow the instructions under “Sandbox Testers” located at  When beta testers receive your app via Test Flight they can make In-App Purchases for free using their regular iTunes account.


To link your In-App Purchases with installs generated via Apple Search Ads check out Kitemetrics by Kitefaster.  Kitemetrics helps you optimize your bids and keywords to increase revenue.

How to create a Today Widget for your iOS App in Swift

This tutorial explains how to create a new Today Widget for iOS in Swift 3 using App Extensions in Xcode.  It covers how to import pods, set up entitlements for inter-app communication via user defaults and custom url schemes.  It also explains how to remove the existing storyboard and implement the today widget view programmatically instead of using Auto-Layout.

Create the Widget

First, Select your project and then create a new target via File, New, Target…

From the iOS tab, choose the “Today Extension” template. Press Next.

Fill in the Product Name and select the appropriate “Embed in Application” target.

From the Extension’s Target General Tab you may want to set your Version and Build to match your main iOS project in order to avoid the following warning when you submit your build to iTunes Connect: CFBundleVersion Mismatch and CFBundleShortVersionString Mismatch.

Remove Storyboards

If you don’t want to use storyboards then delete the “MainInterface.storyboard” file.  From Info.plist, navigate to the NSExtension dictionary and delete the NSExtensionMainStoryboard key.  Add a new key to the NSExtension dictionary titled “NSExtensionPrincipalClass” and for the value choose your main “ViewController.swift” that conforms to the NCWidgetProviding protocol.

Also add the @objc(ViewController) tag to the top of your View Controller class to avoid the error “Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘*** setObjectForKey: object cannot be nil”.

Import Pods

If you would like to use cocoa pods with your widget, then add the new widget target to the Podfile with a new target.  The below example will add the SnapKit pod to the “TodayExtension” widget.

target 'TodayExtension' do
    platform :ios, '9.0'
    pod 'SnapKit', '~> 3.2.0'

Create the View

You can use auto layout to create your today widget view.  The width of the widget is always fixed. By default the today widget is in a compact size and has a fixed height of 110pts.  However, the user can press “Show More” on the widget to expand it larger and “Show Less” to compact it. When in the “Show More” or .expanded state the widget can have a variable height up to the size of the screen.

To know when the user has changed the display mode implement func widgetActiveDisplayModeDidChange(_ activeDisplayMode: NCWidgetDisplayMode, withMaximumSize maxSize: CGSize)
You can determine the active display mode and retrieve the max width and heights available via the below.  If you are in expanded NCWidgetDisplayMode then use .expanded instead of .compact

if self.extensionContext!.widgetActiveDisplayMode == .compact {
    let todayWidth = self.extensionContext!.widgetMaximumSize(for: .compact).width
    let todayHeight = self.extensionContext!.widgetMaximumSize(for: .compact).height


If you would like to share data between the today widget and your container/host application you will need to add the “App Groups” entitlement.  From your project, go to your widget’s Target and select the Capabilities tab.  Turn on App Groups and add a new App Group with a unique name such as “”.  Go to your container/host application’s Capabilities  and turn on App Groups also, select same app group you previously created.

You can now share data between the two apps using UserDefaults suite name.  For example: let sharedDefaults = UserDefaults(suiteName: "")!


Custom URL

If you would like to communicate a press or tap on your Today Widget to open your container/host application you will need to set up a custom url scheme.  Follow the first step on how to register a custom URL scheme here How to open an iOS app with custom URL.

From your today widget you can now use the below sample code to open a custom url:

    self.extensionContext?.open(url, completionHandler: { (Bool) in
        //Handle callback

From your container/host application, implement the following function in AppDelegate.swift to handle the custom url:

func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {
    //do something
    return true




Deep Linking to the iOS App Store

Deep link to an app in the app store:<APP_ID>


Deep link to an apps “Reviews” tab in the app store:<APP_ID>&pageNumber=0&sortOrdering=2&type=Purple+Software&mt=8


Deep link to an apps “Write a Review” page in the app store:<APP_ID>?action=write-review


Deep link to all apps by a developer in the app store:



Remember to replace <APP_ID> with the actual app’s Apple ID. Note that if you are deep linking from the iPhone or iPad you can replace the https:// with itms-apps:// to avoid a redirects.

Maximum String Length for Common Database Fields

When designing a database schema you often have to make decisions on a fields length. Rather then just guess at a number, use the maximum possible value that could conceivably be used for the field. Below is a chart of common database fields such as email address, city, zip code and country name and the maximum possible length value that can be used.

Field Name Character Length Example
email address 254 see RFC5321
city 189 Longest City Name is Bangkok in Thai: Krung Thep Mahanakhon Amon Rattanakosin Mahinthara Ayuthaya Mahadilok Phop Noppharat Ratchathani Burirom Udomratchaniwet Mahasathan Amon Piman Awatan Sathit Sakkathattiya Witsanukam Prasit
zip code 18 Country with the longest zip code format is Chile with NNNNNNN, NNN-NNNN
country 90 Longest country name is Libya’s Arabic name prior to 2013: al-Jam-h-riyyah al-‘Arabiyyah al-L?biyyah ash-Sha‘biyyah al-Ishtir-kiyyah al-‘U-má

Create Apple Search Ads for Multiple Countries (Storefronts)

When Apple Search Ads launched in October 2016 it only displayed ads in the United States.  However, it expanded to multiple English speaking countries on April 25, 2017 to include the United Kingdom, Australia, and New Zealand.  Each country is represented by a different storefront and to get your ad to display in each storefront you need to create a separate campaign for each country.


To get your ad to display in each additional country you will need to create a new campaign and fill in as a minimum the App Name, Storefront, Campaign Name, and Budget.  You will also need to set an initial Ad Group Name, and Default Max CPT Bid.  You can fill out any of the other optional information and then press Start Campaign.  I recommend keeping the Campaign Name short but descriptive and then appending the country name to the end.


All bids are made in the currency that you set when you created your Apple Search Ads account.  So you should adjust you CPT and CPA for each country (storefront) due to exchange rates and taxes.  If different countries have different conversion rates then you’ll want to take that into considerations as well.


If you have multiple Ad Groups you can copy them over to the new campaign.  Go to your original campaign and select the ad group(s) by pressing the check boxes.  Press the Actions menu and select Duplicate.  From here you can choose to copy over the Settings and keywords or just the settings.  Select a destination campaign and a start/end date (optional) and press Duplicate.


To track keyword level attribution and ROI across multiple campaigns check out the Kitemetrics service.

How to set the name of the sender/from/source in Amazon SES

If you are using Amazon Simple Email Service via AWS you can make your emails appear more professional by setting the from name to either a person or company name instead of just the from email address.

To accomplish this via the command line, SDK, or API simply replace the source email address “” with “Company Name <>”.

iTunes Search API Country Codes

The iTunes Search API takes a country code. There are 28 languages that the iOS App Store can be localized into. Below are the ISO 3166-1 alpha-2 country codes for 25 of the main countries that can be used in the country parameter in the iTunes Search API.


How to align UIView to topLayoutGuide in SnapKit

Use topLayoutGuide.snp.bottom to align your UIView to the bottom of the navigation bar or the bottom of the status bar in Swift 3 while using the SnapKit pod.

Use to align your UIView to the top of the tab bar.



How to get expansion APK files with downloader library and market licensing modules to work in Android Studio

Google gives an overview of what expansion APK files are along with some sample code.  However, getting started can be tricky.  Here is an easier to understand set of instructions for importing the necessary libraries as modules in Android Studio.

The following instructions were tested with Android Studio version 2.2.3 on a mac.  Note that on a mac the android sdk folder is at /Library/Android/sdk/.

Download libraries

  • Android Studio…Preferences…Launch Standalone SDK Manager
  • Under Extras, select “Google Play APK Expansion library” and “Google Play Licensing Library”.  Install packages… Accept License and Install.

Import market_licensing library

  • File…New…Import Module…
  • Browse to <ANDROID_SDK>/extras/google/market_licensing/library/, Press OK
  • Rename Module name from library to market_licensing, Press Finish

Import downloader_library

  • Open the <ANDROID_SDK>/extras/google/market_apk_expansion/downloader_library/ file and delete the last line that reads “android.library.reference.1=../market_licensing.”
  • File…New…Import Module…
  • Browse to <ANDROID_SDK>/extras/google/market_apk_expansion/downloader_library/, Press OK and Finish


Import zip library

This step is optional.  If your expansion apk files are in a zip package then this library can be helpful.

  • File…New…Import Module…
  • Browse to <ANDROID_SDK>/extras/google/market_apk_expansion/zip_file/, Press OK and Finish

Add user permissions

Add the following permissions to the AndroidManifest.xml. Note that the documentation only has the WRITE_EXTERNAL_STORAGE permission, but I couldn’t get it to work on my Galaxy S5 test device without the READ_EXTERNAL_STORAGE permission as well.

    <!-- Required to access Google Play Licensing -->
    <uses-permission android:name="" />
    <!-- Required to download files from Google Play -->
    <uses-permission android:name="android.permission.INTERNET" />
    <!-- Required to keep CPU alive while downloading files (NOT to keep screen awake) -->
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <!-- Required to poll the state of the network connection and respond to changes -->
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <!-- Required to check whether Wi-Fi is enabled -->
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
    <!-- Required to read and write the expansion files on shared storage. -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

Also for API 23+ you need to request read/write permissions from the user during application runtime.  You will need to request Manifest.permission.READ_EXTERNAL_STORAGE and Manifest.permission.WRITE_EXTERNAL_STORAGE before downloading or reading the expansion files.

If you don’t have the proper storage permissions you may get a and an error trying to read your .obb file that states “open failed: EACCES (Permission denied)“.


Set up dependencies 

If you build now you may get the following error: “package does not exist”.  Resolve it with the following steps.

  • Right click the downloader_library module from your project view
  • Select “Open Module Settings”
  • Select “Dependencies” tab
  • Press plus sign + then select “3 Module Dependency”
  • Select “market_licensing” and press OK.

Incorporate downloader_sample code into your project

“Most of the time, Google Play downloads and saves your expansion files at the same time it downloads the APK to the device. However, in some cases Google Play cannot download the expansion files or the user might have deleted previously downloaded expansion files. To handle these situations, your app must be able to download the files itself when the main activity starts, using a URL provided by Google Play.”

The sample code to download the expansion APK files manually is at <ANDROID_SDK>/extras/google/market_apk_expansion/download_sample

Copy the source code files, rename them and modify them to meet your needs.  This includes,, and  Also copy layout file main.xml and merge the values file strings.xml with your own.

Modify to make Service Intent explicit

If you build now you may get the following error: “java.lang.IllegalArgumentException: Service Intent must be explicit: Intent { }“.

The root cause of the error is at line 150 of in the market_licensing module.  You can press on the line number in the stack trace “at” or navigate to the file.

add .setPackage("") to the end of the string parameter passed to the intent like so:

new String(
-    Base64.decode("Y29tLmFuZHJvaWQudmVuZGluZy5saWNlbnNpbmcuSUxpY2Vuc2luZ1NlcnZpY2U="))),
+    Base64.decode("Y29tLmFuZHJvaWQudmVuZGluZy5saWNlbnNpbmcuSUxpY2Vuc2luZ1NlcnZpY2U=")))
+    .setPackage(""), // this fixes 'IllegalArgumentException: Service Intent must be explicit'
     this, // ServiceConnection.

Change the minSdkVersion from 3 to 4 in the market_licensing/manifests/AndroidManifests.xml file


Modify DownloaderService to fix WifiManagerLeak error

When you go to generate a signed APK you will get the error “Error:(575) Error: The WIFI_SERVICE must be looked up on the Application context or memory will leak on devices < Android N. Try changing  to .getApplicationContext()  [WifiManagerLeak]“.

The problem is in line 575 of the file within the downloader library.  Modify it as follows:

- mWifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
+ mWifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);


Implementing the downloader service, alarm receiver and starting the download

Follow along with Google’s documentation at to implement the downloader service and alarm receiver.  Scroll down to the section titled “Implementing the downloader service“.


iOS views and their corresponding android views

If you are used to programming in iOS and need to write an android app or vice versa here is a list of iOS views and their equivalent views on android.  You can also use this list to infer the corresponding View Controller and Activity.

iOS android
UITableView ListView
UICollectionView GridView
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