The heartbreak of the Xcode “Undefined symbols for architecture xxx” linker message

As an iOS developer — or any type of software developer — you’re eventually going to run into linker errors. Sometimes they’re easy to fix (i.e., you’re missing an #include for a header file). Sometimes they’re crazy complex, subtle, and very difficult to solve. Today we’ll talk about some tools (file, otool) and techniques (setting library target hardware architectures) you can use for solving difficult Xcode linker errors.

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Using Xcode 7 with the iOS 10 SDK

Today, we’ll be discussing getting an older version of Xcode (7) to work with a newer version of the iOS SDK (10). When done reading this article, you’ll be able to build, link, install, and debug apps in/from Xcode 7 onto iPhones/iPads/iPods running iOS 10. (If you don’t need background, just skip to the solution.) The main reasons for doing this?

  • You have an app built for the last iOS version (9) that has a problem when running in the latest iOS version (10) and you’d like to debug the code; and/or,
  • Apple releases a new beta iOS (10) and beta Xcode (8), you want to see how your current, stable code (built for iOS 9) runs on the new beta iOS (10), but you don’t want to trash your current, stable Xcode (7) installation with the beta Xcode (8).

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Installing multiple versions of Xcode (6, 7, 8) side-by-side, together on the same Mac

Let’s talk about cleanly installing multiple versions of Xcode (6, 7, 8) side-by-side, together on the same Mac desktop, MacBook Pro, or MacBook Air.

Apple keeps moving forward with new Xcode and iOS versions, but some of us in the developer community need the ability to support — or just experiment with — projects in older versions. I’m currently working on an iOS 9 app, developed in Xcode 7 that’s ready to be submitted to the App Store. At this eleventh hour, the last thing I want to do is go through the pain of upgrading to a new iOS SDK in a new Xcode version. I tried building the app and its constituent libraries in Xcode 8, and was presented with tens of compiler and linker errors. Oy… But I do need to to start moving the project to Xcode 8/iOS 10 — and start other projects, check out new features, and get up to speed…

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Welcome to iOS Brain

Stayed tuned as we get our infrastructure together. We’ll be publishing information, tutorials, news, tips, workarounds, reviews, etc., of all things iOS. Look for articles on developing iOS apps using Xcode, Interface Builder, Objective-C, Swift, Adaptive Layout, Auto Layout, and more. Related technologies like Git, BitBucket, GitHub, Photoshop, and Sketch will also be covered.

Don’t be surprised if we go off on tangents into subjects like object-oriented programming, debugging, Agile, Test-Driven Development, Continuous Integration, and more.

Thanks for checking in!

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