Flurry Analytics Portable

We all know about Flurry Analytics, and we know how we can use this with Xamarin in iOS and Android, as well as on Windows Phone.

Well, now there is a portable version that allows the analytics to be implemented in portable class libraries! The portable API abstracts away all the platform differences, but keeps all the power of the Flurry!

This can be found on NuGet and on GitHub.

Features

The features of the portable API are the same as the native API’s, as the portable is more of an abstraction than anything else. So along with all the native features, there are a few nice new once that make the API easier to use.

This is the primary advantage of this library, it allows the analytics to be implemented in portable projects. This is especially useful if you are using a cross-platform framework, such as MvvmCross. There is a sample that you can check out that makes use of all the features.

Starting Sessions

Although the library is portable, each platform needs to start the analytics session natively/differently:

For iOS, it is very simple call StartSession from the AppDelegate:

    AnalyticsApi.StartSession("[API KEY]");

For Android, there are two ways to do this. Either by overriding the OnStart and OnStop methods from each Activity:

    // in OnStart
    AnalyticsApi.StartSession(this, "[API KEY]");

    // in OnStop
    Analytics.EndSession(this);

Or, by using the IActivityLifecycleCallbacks for the Application. This way allows you to start and end the session without having to implement the logic in each Activity. However it is only available from API Level 14 / Android 4.0 / Ice Cream Sandwich.

For Windows Phone, starting the session is done by attaching the StartSession method call to the Launching and Activated events:

    PhoneApplicationService.Current.Launching += (sender, args) => AnalyticsApi.StartSession();
    PhoneApplicationService.Current.Activated += (sender, args) => AnalyticsApi.StartSession();

For each of the platforms, there is also a way to pass the key in to the API, but only start the session later:

    // somewhere in the code
    AnalyticsApi.ApiKey = "[API KEY]";

    // and then a little later
    AnalyticsApi.StartSession();

There is also a boolean property, IsSupported, that will return true if the platform supports Flurry Analytics:

    if (!Analytics.IsSupported)
        Debug.WriteLine("PLatform does not support Flurry, nothing will be tracked.");

Setting Up Analytics

There are a few methods that hide the platform differences. Some examples of this are in the setting of user details, such as SetAppVersion, SetUserId, SetLocation, SetAge and SetGender.

Not only that, there are a few methods that specify how Flurry should communicate, such as SetSessionContinueTimeout and EnableSecureTransport.

Usually these methods should be called before starting the session.

Logging Events & Errors

Along with tracking basic analytics, events and errors can be tracked. There are a few methods that support this: LogPageView, LogEvent, LogTimedEvent, EndTimedEvent and LogError.

Logging timed events has been made much easier by implementing a new pattern for doing this. By calling LogTimedEvent in a using block, you can end the event in case of any exceptions as well as removing an extra call:

    using (AnalyticsApi.LogTimedEvent("EventId"))
    { 
        // perform a long running task
    } 

Before, you would have to ensure that you called EndTimedEvent to avoid any problems:

    try
    {
        AnalyticsApi.LogTimedEvent("EventId");
        // perform the long running task
    }
    finally
    {
        AnalyticsApi.LogTimedEvent("EventId");
    }

Parameters can also be passed with the events using a simple Dictionary:

    var parameters = new Dictionary<string, string> 
    {
        {"ParameterKey", "ParameterValue"}
        {"AnotherParameterKey", "AnotherParameterValue"}
    };
    AnalyticsApi.LogEvent("EventId", parameters);

Binding Flurry Analytics with Xamarin.Android

This week, I needed to use Flurry Analytics in my Xamarin.iOS and my Xamarin.Android apps, but there was no .NET SDK for these platforms. Flurry did provide a SDK for each platform, but it was the native libraries, which cannot be used directly in .NET. Given this, I decided to bind those native libraries using Xamarin.iOS and Xamarin.Android.

I have split this project up into four parts:

  1. Introduction and Pre-requisites
  2. Xamarin.iOS binding
  3. Xamarin.Android binding
  4. Flurry.Analytics in the wild

After binding the iOS SDK for Flurry Analytics, we are going to move onto the Android release. This task needs only one thing from the downloaded SDK:

  • [Android-sdk-path]/Android 4.1.0/FlurryAnalytics/FlurryAnalytics-4.1.0.jar

Of course, the version numbers may change for later releases. The java archive file (.jar) is going to be used to generate the .NET interfaces and enums, and then be embedded in the resulting assembly.

Just before we do the real binding, we should just create our C# solution for the Xamarin.Android binding. Just create a new project/solution and select the Android “Bindings Library” template. For my project name I used Flurry.Analytics.Android, but you could use anything.

The default project has a few files and directories in it, we will have a look at each one in depth as we go through the binding steps:

  • /Additions/ (this allows you to add arbitrary C# to the generated classes
    before they are compiled)
  • /Properties/AssemblyInfo.cs (the usual assembly information attributes)
  • /Jars/ (this directory is for Android .jars)
  • /Transforms/EnumFields.xml (this allows you to map Java int constants to C# enums)
  • /Transforms/EnumMethods.xml (this allows changes to method parameters and return types from Java int constants to C# enums)
  • /Transforms/Metadata.xml (this allows changes to be made to the final API)

Creating the Initial Binding

This step will involve just adding the jar to the project, and letting the compiler do it’s thing, but we will almost always have to go in and tweak a few things in the Metadata.xml.

So, first things first, add the jar file to the project and compile. The build will probably fail with error messages containing single character methods and types. This is because the actual jar file has been obfuscated. However this can easily be fixed.

The way the generation works is that there is a two step process, there is a tool that generates a bunch of xml files from the jar file. These xml files are then used to generate C# code. The Metadata.xml sits in between the two steps and can be used to transform the generated xml before the C# generation.

Tweaking the Generated Binding (Manifest.xml)

As we can see that the build fails on obfuscated types, we can remove these. The removal is safe as we are only preventing the .NET binding from being created, not actually removing the underlying Java members. And, as these items have been obfuscated, we can safely assume that we aren’t supposed to be accessing them anyway.

But, instead of removing each member or type that appears, we can use a great tool that will decompile the jar file and show us exactly what types are internal and what types we should be binding. I use JD-GUI, which is a free Java decompiler. They also have a nice online version, JD-Online. What we can do is to just upload the jar file here and see what’s inside:

  • com.flurry.android.impl.analytics.*
  • com.flurry.android.*
  • com.flurry.sdk.*

As we can see, the impl and sdk branches contain internal and obfuscated types, so we can remove those:

<remove-node path="/api/package[starts-with(@name, 'com.flurry.sdk')]" />
<remove-node path="/api/package[starts-with(@name, 'com.flurry.android.impl')]" />

After this, the build should now succeed and we will have an assembly that we can use. However, there are still some types that we can remove to clean the API a bit: InstallReceiver and Constants. InstallReciever is not used by the consumer, so this is safe to remove, but Constants is still used. If we remove this, then the consumer will not have access to the values on the type. We can see that Constants just contains the values representing male, female and unknown.

To remove the InstallReciever, we can add this line to Metadata.xml:

<remove-node path="/api/package[@name='com.flurry.android']/class[@name='InstallReceiver']" />

For the Constants type, we will do something different.

Managing the Enumerations (Additions & EnumFields.xml)

As we clean up the API, we want to remove the Constants type and replace it with an enum. One way to do this is to use the EnumFields.xml:

<mapping clr-enum-type="Flurry.Analytics.Gender" jni-interface="com/flurry/android/Constants">
    <field clr-name="Male" jni-name="MALE" value="1" />
    <field clr-name="Female" jni-name="FEMALE" value="0" />
    <field clr-name="Unknown" jni-name="UNKNOWN" value="-1" />
</mapping>

This will generate a nice enum for us, but this does leave an unused interface IConstants. As this is a very small library, we can do this mapping slightly differently. First we remove the entire Constants type in the Metadata.xml:

<remove-node path="/api/package[@name='com.flurry.android']/interface[@name='Constants']" />

Then, we can create the enum in the /Additions/ directory. To do this, add a new file (for example called FlurryAgent.cs) under this directory and add the enum:

public enum Gender
{
    Male = 1,
    Female = 0,
    Unknown = -1
}

Now there is one last thing to do before the API definition is complete. There is a SetGender method on the type FlurryAgent, which takes the type sbyte. It is not intuitive to use the Gender enum here, so we can fix this in a two step process. First we will create an overload in the FlurryAgent.cs file that accepts a Gender enum member as an argument:

public partial class FlurryAgent
{
    public static void SetGender(Gender gender)
    {
        FlurryAgent.SetGender ((sbyte)gender);
    }
}

And, what we can do is also hide the original member as the new overload is good enough:

<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='setGender']" name="visibility">internal</attr>

And with this, our binding is complete, although we can do a few nice changes to the namespace and parameter names.

Changing Parameter Names

Now that we have the binding complete, we can see that it is using the namespace Com.Flurry.Android, which is no .NET-like at all. We can change this to something better:

<attr path="/api/package[@name='com.flurry.android']" name="managedName">Flurry.Analytics</attr>

This maps the com.flurry.android package name to the neat Flurry.Analytics namespace. One last thing is to fix the parameter names. Sometimes you can use the JavaDocs, but in this case, I couldn’t get it to work. Doing it manually is not hard, but it is boring and time consuming, but here are a few.

This is the usual mapping:

<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='onStartSession']/parameter[@name='p0']" name="name">context</attr>
<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='onStartSession']/parameter[@name='p1']" name="name">apiKey</attr>
<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='onEndSession']/parameter[@name='p0']" name="name">context</attr>

If there are complicated parameter types (note the &lt;):

<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='logEvent']/parameter[@name='p1' and @type='java.util.Map<java.lang.String, java.lang.String>']" name="name">parameters</attr>

If there are overloads with different parameter types:

<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='onError']/parameter[@name='p2' and @type='java.lang.Throwable']" name="name">exception</attr>
<attr path="/api/package[@name='com.flurry.android']/class[@name='FlurryAgent']/method[@name='onError']/parameter[@name='p2' and @type='java.lang.String']" name="name">errorClass</attr>

After doing this for all the members, the binding is now complete.

Finishing Up

So far we have defined our API, added any additional logic or types, added the native library and added parameter names. This is all that is needed, so our library should build fine now and we should be able to use it in an Xamarin.Android app:

// the methods
FlurryAgent.StartSession(this, "PQSZJRK4B5BW8Q7YQQXF");

// the properties that we changed back into methods
string version = FlurryAgent.ReleaseVersion;

// the extra method that we added
FlurryAgent.SetGender (Gender.Male);

Flurry.Analytics for Xamarin

The Flurry Analytics Agent allows you to track the usage and behavior of your Android, iOS or Windows Phone application on users’ phones for viewing in the Flurry Analytics system. It is designed to be as easy as possible with a basic setup complete in few minutes.

Features

There are many features available in the Flurry Analytics API, such as:

  • Session tracking
  • Event logging, with optional parameters
  • Page View tracking
  • Demographics tracking, such as age, gender and user id
  • Location tracking
  • App version tracking
  • And much more…

Getting Started

The setup for all the platforms is very easy with only a few steps:

Android

  1. Add the INTERNET permission to AndroidManifest.xml.
  2. Add FlurryAgent.OnStartSession(this, "YOUR_API_KEY"); to the OnStart method of the Activity or Service.
  3. Add FlurryAgent.OnEndSession(this); to the OnStop method of the Activity or Service.

iOS

  1. Add FlurryAgent.StartSession("YOUR_API_KEY"); to the FinishedLaunching method of the Application Delegate

Windows Phone

  1. Add ID_CAP_NETWORKING and ID_CAP_IDENTITY_DEVICE capabilities to WMAppManifest.xml.
  2. Add FlurryWP8SDK.Api.StartSession("YOUR_API_KEY"); to Launching and Activated events of the Application.

And that’s it, your mobile app will start sending activity usage statistics to the Flurry servers!

Advanced

Flurry Analytics SDK supported versions:

  • SDK for iOS supports Xcode tools 4.5 and above
  • SDK for Android supports Android API level 10 (Gingerbread) and above
  • SDK for Windows Phone supports Windows Phone 8 and above

Downloading

The Flurry.Analytics API is available on NuGet.org (Flurry.Analytics) and on GitHub (mattleibow/Flurry.Analytics).

It is released under the same license as the native libraries.

The Making Of

You can read up on how the binding was created in my blog:

  1. Introduction and Pre-requisites
  2. Xamarin.iOS binding
  3. Xamarin.Android binding
  4. Flurry.Analytics in the wild

Binding Flurry Analytics with Xamarin

Over the last few days I have been creating a Xamarin.iOS and Xamarin.Android binding for Flurry Analytics SDKs. Flurry Analytics is a neat little library that allows for tracking of your app usage and various user stats.
And, because I really enjoyed my time doing this, I thought that I will share just a bit of the fun times and the not-so-fun times.

I have split this project up into four parts:

  1. Introduction and Pre-requisites
  2. Xamarin.iOS binding
  3. Xamarin.Android binding
  4. Flurry.Analytics in the wild

Pre-requisites

Before we start any coding, we need to get all our tools and files needed for the actual binding tasks.

I was using both Windows 8, with Visual Studio, and Mac OS X with Xamarin Studio. You can bind the Android library on either platform, but for iOS, it is easier to use the Mac. In this case, I will use the Mac for both iOS and Android.

Some of my very excellent sources for this process were the actual Xamarin documentation:

But, along with this info, there are just a few things that you may need. Firstly, it is good to update your Xamarin Studio to the latest stable release as this makes sure that all potential problems are minimized from the start.

Then, the next cool tool to get hold of is, Objective Sharpie, for binding iOS libraries. This tool is quite nifty for quickly generating the .NET interfaces from the Objective-C header files. It uses the header files not the actual compiled native library. The Xamarin docs on Objective Sharpie has a brief walkthrough on how to use the tool, so I will assume you know how to use it.

After we have all our tools ready to go, we need those SDKs from Flurry.

What I did was to create a free account by Flurry, and then created an Android and iOS Application using their dashboard. You have to have an application before they will let you download their SDKs. This step is pretty straight forward, so I won’t go into it here right now. Once you have created and downloaded the SDKs, you can extract them to a nice location for reference.

Now to get started with the real work…

But, as this is quite a long process, I will be splitting this article into this intro, the iOS binding and the Android binding. So, enjoy!

Binding Flurry Analytics with Xamarin.iOS

This week, I needed to use Flurry Analytics in my Xamarin.iOS and my Xamarin.Android apps, but there was no .NET SDK for these platforms. Flurry did provide a SDK for each platform, but it was the native libraries, which cannot be used directly in .NET. Given this, I decided to bind those native libraries using Xamarin.iOS and Xamarin.Android.

I have split this project up into four parts:

  1. Introduction and Pre-requisites
  2. Xamarin.iOS binding
  3. Xamarin.Android binding
  4. Flurry.Analytics in the wild

The first thing we are going to bind is the iOS SDK for Flurry Analytics. This task needs two things from the downloaded SDK:

  • [iOS-sdk-path]/Flurry-iOS-5.2.0/Flurry/Flurry.h
  • [OS-sdk-path]/Flurry-iOS-5.2.0/Flurry/libFlurry_5.2.0.a

Of course, the version numbers may change for later releases. The header file (.h) is going to be used to generate the .NET interfaces and enums. The library (.a) is going to be used in the project.

Just before we do the cool things, we should just create our C# solution for the Xamarin.iOS binding. Just create a new project/solution and select the “iOS Binding Project” template. For my project name I used Flurry.Analytics.iOS, but you could use anything.

The default project has a few files in it, we will have a look at each one in depth as we go through the binding steps:

  • ApiDefinition.cs (this is for the generated .NET interfaces from Objective Sharpie)
  • AssemblyInfo.cs (the usual assembly information attributes)
  • Extras.cs (this is for any additional changes that are needed for the bound types)
  • StructsAndEnums.cs (this is for any extra types that you wish to include in the final assembly)

Creating the Initial Binding

This step will involve using Objective Sharpie to get us started, but we will almost always have to go in and tweak a few things.

So, first things first, open Objective Sharpie and start the wizard. Select the Flurry.h header file, and I used the namespace Flurry.Analytics. After saving your file somewhere, we can start the tweaks. I don’t save the result into my solution as the amount of tweaks needed is high enough that I like to have a before and after file. Also, this library is very small. But, there is no reason why you couldn’t just save over the ApiDefinition.cs file in you project.

Before we start, here is a snippet from the Flurry.h file:

    // an enum
    typedef enum {
        FlurryLogLevelNone = 0,
        FlurryLogLevelCriticalOnly,
        FlurryLogLevelDebug,
        FlurryLogLevelAll
    } FlurryLogLevel;

    // the main class
    @interface Flurry : NSObject {
    }
    // ...
    + (void)setAppVersion:(NSString *)version;
    + (NSString *)getFlurryAgentVersion;
    + (void)startSession:(NSString *)apiKey;
    // ...
    @end

In this snippet of Objective-C goodness, there is an enum named FlurryLogLevel and an @interface named Flurry. This will translate into a C# enum and class respectively. It is also good to note that all the methods on this particular type will be static.

The generated C# for this snippet is:

    // the enum
    public enum FlurryLogLevel : [unmapped: unexposed: Elaborated] {
        None = 0,
        CriticalOnly,
        Debug,
        All
    }

    // the main class
    [BaseType (typeof (NSObject))]
    public partial interface Flurry {
        // ...
        [Static, Export ("appVersion")]
        [Verify ("ObjC method massaged into setter property", "Flurry/Flurry.h", Line = 61)]
        string AppVersion { set; }

        [Static, Export ("getFlurryAgentVersion")]
        [Verify ("ObjC method massaged into getter property", "Flurry/Flurry.h", Line = 80)]
        string GetFlurryAgentVersion { get; }

        [Static, Export ("startSession:")]
        void StartSession (string apiKey);
        // ...
    }

As you can see, the generated file is similar, but not quite the same.

Tweaking the Generated Binding (ApiDefinition.cs)

After we generated our C# files, there are several things to note:

  • This code doesn’t compile at all
  • A good few of our methods are set to properties, especially note the setter-only ones
  • There is a [Verify(...)] attribute which doesn’t even exist
  • Some [Export] attributes have a value that ends in a colon (:), and others do not
  • The type is not a class but an interface
  • The base type is specified as a [BaseType] attribute
  • The enum has the item prefixes removed

This is quite a list here, but not all are bad. Objective Sharpie can’t generate perfect code as Objective-C is not C#, so there will always be human intervention. In these cases, it will generate what it thinks to be best and then let you know.

The [Verify] attribute is one way that Objective Sharpie lets you know that it changed something. In this instance, it is letting us know that it changed the setAppVersion method into a property. This is because usually there is both a getter and a setter method for a Objective-C property. But in this case, it is actually a method.

As you may note, these properties have a slightly different [Export] attribute in that these members don’t end in a colon. This is valid for Objective-C property setters, but as this is a method, we should add a colon back. It is also valid for methods that take parameters.

So, to fix those properties, remove the [Verify] attribute. We should also fix the exported name, and for the setter property, add the colon back in.

    [BaseType (typeof (NSObject), Name = "Flurry")]
    public partial interface FlurryAgent {

        [Static, Export ("setAppVersion:")]
        void SetAppVersion (string version);

        [Static, Export ("getFlurryAgentVersion")]
        string GetFlurryAgentVersion ();

        [Static, Export ("startSession:")]
        void StartSession (string apiKey);

    }

As you can see here, I corrected the SetAppVersion write-only property by transforming it into a void method that exports to setAppVersion:. Note the full name and colon as this method takes a parameter.

Also, I needed to fix the GetFlurryAgentVersion read-only property by transforming it into a string method that exports to “getFlurryAgentVersion”. Note the lack of colon as this method takes no parameters.

And finally, I decided I wanted my final class to be called FlurryAgent to avoid confusion with the namespace as well as indicate that it was the Agent. In order to do this, All I needed to do was to rename the type and add the Name property in the attribute with a value of "Flurry".

The reason for adding this property is, after changing the type name, the binding no longer will be able to find the underlying Objective-C type. Usually the binding will use the default name if none is provided, the C# class name. After changing it, it no longer reflected the Objective-C type name, hence the new property.

Managing the Structures and Enumerations (StructsAndEnums.cs)

The last thing to fix, in the generated code, is the enum.

This is simple to do, just remove the strange attribute-like bit: [unmapped: unexposed: Elaborated].

One of the nice things of Objective Sharpie is that it removes the enum prefixes and just uses the relevant bits. For example the original item was FlurryLogLevelNone, but this is now just None.

The final enum looks like this after it has been moved to StructsAndEnums.cs:

    public enum FlurryLogLevel {
        None = 0,
        CriticalOnly,
        Debug,
        All
    }

So far, all our generated code has been moved into either, ApiDefinitions.cs (the class), or StructsAndEnums.cs (the enum). We are still not complete yet, but we are nearly there.

Additional Binding Code (Extras.cs)

Once we have the basic binding done, we can always extend what the native library provided with extra features. This is done by adding new source files to the project.

For example, if for some reason you need to add any extra bindings to the library, say to access a private member or even just to make the new API cleaner and more .NET-like.

For example you could do something like this:

    public partial class FlurryAgent : NSObject {
        public static void LogTimedEvent (string eventName, Action action) {
            try {
                FlurryAgent.LogEvent (eventName, true);
                action(); // do our task
            } catch {
                FlurryAgent.EndTimedEvent (eventName, null);
                throw;
            }
        }
    }

What is happening here is that I am adding a new method to the final .NET assembly. This method can make use of the methods in the API definition interface. In this particular example, I am adding a method that can take an Actionand make sure that we fire a ‘starting’ and then an ‘ending’ event to the Flurry servers. This is a new bit of functionality that can be baked right into the binding assembly.

Working with the Native Library (.a)

This step is actually quite easy, just add the native library (.a) to the project, and you are almost done.

When you add the native library to the project, Xamarin Studio will create a new .linkwith.cs file that matches the library name. For example with Flurry, I added the libFlurry_5.2.0.a library to my project and it generated a libFlurry_5.2.0.linkwith.cs.

This new file is the last bit that needs to be done. It is for the linker when using this library in an iOS app. It usually will contain only a single line, a single [LinkWith] attribute. This attribute allows you to specify what targets this library can be used with, what extra iOS frameworks are needed, etc:

    [assembly: LinkWith (
        "libFlurry_5.2.0.a", 
        LinkTarget.Simulator | LinkTarget.ArmV6 | LinkTarget.ArmV7 | LinkTarget.ArmV7s, 
        ForceLoad = true)]

This is the default line, split for readability, and usually it is all that is needed. What this does is say that the linker must use the libFlurry_5.2.0.a native library as well as this library can be used on the Simulator and all the devices. The ForceLoad is used by the Xamarin.iOS linker, and specifies a linker flag. According to the documentation, this should always be true for now.

But just before we finish up, we need to add any required frameworks. Without this, there will be strange happenings…but different depending the configuration.

If building for Debug, the app will launch, but nothing will happen at all. The methods can be called and everything, but no actions will take place.

If building for Release, the linker will throw an error:

Error MT5211: Native linking failed, undefined Objective-C class: _OBJC_CLASS_\$_Flurry.
If ‘_OBJC_CLASS_\$_Flurry’ is a protocol from a third-party binding, please check that it has the [Protocol] attribute in its api definition file, otherwise verify that all the necessary frameworks have been referenced and native libraries are properly linked in.

This error is giving us lots of information for @protocol, but as we don’t have any in our project (recall the @interface), we can safely ignore the first part of the second message and focus on the ‘frameworks’ part. According to the Flurry documentation, the Security.framework is required and the SystemConfiguration.framework is optional, but recommended.

So, I added both frameworks, using the Frameworksproperty:

    [assembly: LinkWith (
        "libFlurry_5.2.0.a",
        LinkTarget.Simulator | LinkTarget.ArmV6 | LinkTarget.ArmV7 | LinkTarget.ArmV7s, 
        ForceLoad = true, 
        Frameworks = "SystemConfiguration Security")]

As shown here, the frameworks are space-separated and do not have the .framework extensions.

Finishing Up

So far we have defined our API, added any additional logic or types, added the native library, set up the linker and specified the frameworks. This is all that is needed, so our library should build fine now and we should be able to use it in an Xamarin.iOS app:

    // the methods
    FlurryAgent.StartSession("PQSZJRK4B5BW8Q7YQQXF");

    // the properties that we changed back into methods
    FlurryAgent.GetFlurryAgentVersion ();

    // the extra method that we added
    FlurryAgent.LogTimedEvent ("started", () => {
        // ...
    });

Under the Hood

One thing to know is that the iOS binding project is actually not really compiled directly, but are a series of stages. Each file actually has a different build action.

The first stage to building the binding is to build a reference assembly with the files:

  • ApiDefinition.cs (with build action ObjcBindingApiDefinition)
  • StructsAndEnums.cs (with build action ObjcBindingCoreSource)

Next, this assembly is then reflected to generate the actual binding code. This generated code is then compiled with the rest of the files:

  • Extras.cs (with build action Compile)
  • StructsAndEnums.cs (again with build action ObjcBindingCoreSource)
  • libFlurry_5.2.0.linkwith.cs (with build action Compile)
  • libFlurry_5.2.0.a (with build action ObjcBindingNativeLibrary but is actually just a resource)

An example of the generated code in the second stage, the interface member void StartSession(string) is actually used to generate a big block of code:

    [Export ("startSession:")]
    [CompilerGenerated]
    public static void StartSession (string apiKey)
    {
        if (apiKey == null)
            throw new ArgumentNullException ("apiKey");
        var nsapiKey = NSString.CreateNative (apiKey);

        MonoTouch.ObjCRuntime.Messaging.void_objc_msgSend_IntPtr (class_ptr, selStartSession_Handle, nsapiKey);
        NSString.ReleaseNative (nsapiKey);
    }

This is all the magic that happens under the hood to redirect values from the managed .NET to the underlying native library.