How Xamarin Works

Now that we've discussed some of the challenges with mobile development and 0:00 how Xamarin can help, let's look at how it works. 0:04 Each platform has its own feature set, application framework, and 0:09 execution differences. 0:13 Xamarin has Base Class Libraries, or 0:16 BCLs which provide many features usually found in the .NET framework. 0:18 They're implemented on the native platform and exposed through the BCL. 0:24 For example, in the BCL there's support for Streams, IO, 0:29 XML, Databases, and Networking. 0:32 These provided base class libraries have the same signature as the dot net BCL. 0:38 So we can write the same code for each platform. 0:44 There are libraries provided by Xamarin that are included in each platform project 0:47 that provide implementation for platform SDKs. 0:52 All these features are plugged into Visual Studio and 0:57 include IntelliSense, tools and compilation features. 1:00 Xamarin provides bindings to the native libraries and SDKs for each platform. 1:06 Bindings are strongly typed and are designed to follow C# standards. 1:12 This gives developers a single consistent programming syntax 1:18 regardless of the target platform. 1:22 For example, Java does not have a concept of properties. 1:25 So you use Get and Set methods to update a class variable. 1:29 But, Xamarin wraps them in a property to match C# standards. 1:34 Other than that, 1:38 converting Java code to C# is relatively simple cuz they share a lot of syntax. 1:39 For Objective-C developers, there are many differences between Objective-C and C#. 1:46 So if you're converting from Objective-C, 1:52 there's some articles in the teacher's notes to help with the transition. 1:54 Xamarin also allows us to create an interop between 1:58 any of our favorite Objective-C or Java libraries. 2:02 Using a declared syntax we can bind any pre-existing library, and 2:06 make it look like a C# class and use it in our app. 2:11 Compilation is where all the magic happens, so 2:16 we'll spend a few minutes talking about how it works. 2:19 As I said earlier, Android and iOS have fundamental execution differences. 2:22 Android uses a just in time execution model or 2:27 JIT which means that it compiles to an intermediate language 2:30 that is interpreted and executed when the app launches. 2:35 iOS on the other hand uses an ahead-of-time execution model or 2:40 AOT which means everything is compiled directly to native assembly code and 2:44 nothing is interpreted. 2:49 All of this compilation happens through special platform specific MS built targets 2:51 that put all the pieces together and produce the executable artifacts. 2:57 It's important to know when compiling for iOS you need a Mac. 3:02 Because Apple's licensing does not permit compiling on any other platform. 3:06 Android requires your target SDKs and 3:12 tools to be on your machine, which can be downloaded when needed. 3:15