# How to: Handoff to a Xamarin iPhone app from Apple Watch

There are two ways to activate the parent (aka container) app from an Apple Watch app. You can either directly activate the container app using WKInterfaceController.OpenParentApplication or you can use Handoff.

Using Handoff is a little more complex …

Disclaimer: This is just a hack. I’m not in any position to make announcements about stuff, but Xamarin loves F# and I’m sure that better solutions than this are forthcoming. But this was fun to get running, so…

Xamarin just released it’s Preview of Watch Kit support …

I wrote a program to automatically generate class diagrams, filtered by coupling. Here is the result for CoreBluetooth in iOS:

You can see there are clusters around CBPeer, CBPeripheral, and CBCentral and that CBCharacteristic is another class with lots of references.

Obviously, huge class diagrams are more noise than signal …

Today comes the shitty news that Dr. Dobb's (...Journal of Computer Calisthenics and Orthodontia) is shutting down.

I would not have had the career I have had without DDJ: first as an inspiration, then as a competitor, and then as the last torch of technically rigorous, personally-voiced but professionally edited …

[embed]https://www.youtube.com/watch?v=2-v4jdQJ5Wo&feature=youtu.be&a[/embed]

Video from my Xamarin Evolve talk on using F# for programming mobile apps, in which I argue that functional and object-oriented programming are two great paradigms that pair great together.

Things are kind of busy what with Evolve being only 40 days away and iOS 8 coming down the pipe, but I thought I'd share the easy hack that allows you to program Xamarin.Forms with F#.

(Of course, Xamarin loves F# and official support and templates and documentation and …

One of the more interesting frameworks in iOS 8 is Health Kit, system-wide persistent storage for health-related information. I'm just beginning to explore the namespace myself, but thought I'd walk through the steps you need to manipulate Health Kit with Xamarin.

Because health-related information is so sensitive, developing for Health …

In C# (and F#), one can define extension methods on interfaces. These extension methods can have implementations, which can be used as default implementations for implementors of the extension. I haven't heard a name for this technique.

Example:

[code lang="csharp"]
interface IFoo
{

}

static class IFoo_Extensions
{
public static void …

As of iOS 8, the user has to provide explicit permission for apps to respond to local notifications. This means that now, the first time the program is run, you need to run code such as:

[code lang="fsharp"]
//F#
UIUserNotificationSettings.GetSettingsForTypes(
UIUserNotificationType.Alert
||| UIUserNotificationType.Badge
||| UIUserNotificationType.Sound,
new NSSet …

It's F# Week at Xamarin. Also, in the US, it's only a 4-day work-week. F# saves 20% of your time. QED.

Anyway, I don't have any actually interesting F# to share, but I recommend:

• Mike Bluestein's Scene Kit in F# demo, and
• Frank Kreuger's awesome demo of using F# interactively …