Microsoft Offers Open-Source Windows Bridge for iOS

Microsoft releases an early preview of its tool for bringing iOS apps to the Windows platform and also open-sources the technology.

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Microsoft this week delivered on its vision of building bridges to non-Microsoft platforms with an early version of its bridge for running iOS apps on Windows.

At its Build 2015 conference in San Francisco in April, Microsoft announced a series of "bridging" technologies to enable developers to bring their existing iOS, Android, Web and desktop code and skill sets to the Windows Store. Now the company has released an early version of its Windows Bridge for iOS and in turn has open-sourced the technology under the MIT license.

The Windows Bridge for iOS, formerly known as "Project Islandwood," is still a work-in-progress. Microsoft delivered this early version on Aug. 6, but the final release will come later this fall. Microsoft hopes the open-source community will help shape the technology in the meantime. The extra time also will enable the bridge to take advantage of new tooling capabilities that will ship with the upcoming Visual Studio 2015 Update, said Kevin Gallo, vice president of the Windows Developer Platform, in a blog post.

"Microsoft's move here illustrates that the only serious way to engage developers today is with open source," said Al Hilwa, an analyst at IDC. "The Visual Studio team is clearly one of the lead groups at Microsoft in transforming how the giant works with open source."

The Windows Bridge for iOS enables iOS developers to create Windows apps using their existing Objective-C code and skills. In a separate blog post, Salmaan Ahmed, Microsoft's program manager for Windows Bridge for iOS, said the bridge comprises four components: an Objective-C compiler, an Objective-C runtime, iOS API headers and Visual Studio IDE integration.

Ahmed said Visual Studio will include a compiler that knows how to take Objective-C code and compile it into a native Universal Windows app. "For now, we will provide early drops of the compiler binary via GitHub—we're not open sourcing the compiler," he said. The compiler will ultimately ship as part of a Visual Studio 2015 update scheduled in the fall, he added.

The Objective-C runtime will provide language features such as message dispatch, delegation and automatic reference counting. Microsoft also will provide broad iOS API compatibility. And with Visual Studio IDE integration, Microsoft is providing tooling that imports Xcode projects and ties into the Windows developer tools in Visual Studio 2015 and the Windows SDK.

The iOS bridge supports both Windows 8.1 and Windows 10 apps built for x86 and x64 processor architectures, and Microsoft soon will add compiler optimizations and support for ARM, which adds mobile support, Gallo said.

He also provided updates on the other "bridges" Microsoft introduced at Build. Gallo said the Windows Bridge for Web apps, "Project Westminster," is live and available with the release of Windows 10 and Visual Studio 2015.

Meanwhile, the Windows Bridge for Android, or "Project Astoria," is currently available as a technical preview by invitation only. And the Windows Bridge for Classic Windows apps, "Project Centennial," which will make it possible to package and publish your current .NET and Win32-based Windows applications to the Windows Store, will be ready for public testing next year, Gallo said.