Even though Swift is the primary coding language across the Apple ecosystem now, there is still an awful lot of iOS apps coded in Objective-C out there. Typically, the larger and older the app, the more likely that there is still a bunch of Objective-C language powering various bits of the app behind the scenes.
Don’t get me wrong, Objective-C is a wonderful programming language that worked quite well for many years, but its flaws have been exposed with the rapidly evolving technology. Some of the obvious flaws include a lack of flexibility and syntax restrictions, to name a few.
Thus, there has been a massive push from Apple to migrate all iOS apps to Swift. Unfortunately, the migration from Objective-C to Swift isn’t a straightforward affair because the latter can’t simply sit on top of an Objective-C core without friction. In reality, migrating from Obj-C to Swift requires proper planning and a deep understanding of both languages.
This article outlines the key steps involved in migrating from Objective-C to Swift with a special focus on what to prioritize first, what might go wrong and what is rarely worth rewriting.
What Usually Goes Wrong in These Migrations?
The most common challenges in Objective-C to Swift migration often stem from interoperability and a massive underestimation of the effort required to engineer a successful transition.
From a technical perspective, the biggest challenge is dealing with bridging header and interoperability issues. The bridging header allows the two languages to communicate efficiently, but it can also become a source of errors and bugs, especially with relatively complex dependencies. Issues usually arise when Swift features, such as structs aren’t fully compatible with Obj-C requiring manual workarounds that we often refer to as shims.
From a team readiness and skills gap perspective, many people think that Swift is simply Objective-C with a different syntax which is not the case. Swift has a wide range of features and functionalities, such as immutability, value types, protocol-oriented design and strict type safety, that can be unfamiliar to teams that don’t deeply understand the language.
Steve Barnegren, an iOS developer based in London says that when migration begins without clear team readiness, you risk ending up with Swift code that mimics Objective-C habits. This leads to inconsistent style, overreliance on reference types, misuse of optionals and avoidance of Swift’s strongest features.
What to Prioritize First
A successful migration focuses on unlocking the most leverage. If you prioritize correctly, then you will see immediate gains in developer velocity and code safety without destabilizing production systems. Here is what consistently deserves attention first:
Clean up and modernize Objective-C before migration: It is essential to update your legacy Objective-C files, classes and modules to modern standards before you start migration. This is important because it simplifies the transition and reduces translation friction.
Focus on interoperability and bridging: I highly recommend using Xcode’s bridging headers intentionally. One thing I have realized from my experience is that explicit exposure of Objective-C APIs to Swift plays a critical role in ensuring proper linkage and reducing runtime bugs. So, this is something I’ll definitely prioritize at first.
Prioritize high-value, independent modules: The migration process doesn’t need to be overly complicated. Consider starting with smaller, self-contained components or utility classes. I like this approach because it reduces dependency on complexity and helps verify correct integration before tackling more interlinked areas.
Prioritize migration rules, not goals: Sometimes, the most critical priority during migration is the process, not the code. Teams that succeed define migration rules early. What language owns which layers? When is code rewriting allowed and when is it forbidden? What signals justify migrating a legacy component? It is essential to have these guardrails in place to avoid drifting into inconsistency.
What Is Rarely Worth Rewriting
Two things are not worth rewriting when migrating from Objective-C to Swift: well-functioning UI and business logic, and third-party libraries that still work fine. If the UI and business logic are functioning well and well tested, you can leave them in Objective-C and simply interoperate.
Similarly, many Objective-C frameworks still function perfectly even after migrating to Swift. Rewriting them for the sake of eliminating Objective-C often wastes time and may even introduce new bugs to your code.
Some Tips for a Successful Migration
Identify which modules of the system/app are most actively maintained and begin the migration with smaller, less complex components. The primary goal here is to reduce initial integration risks.
Apply Apple’s Incremental Adoption approach using bridging headers to ensure that new features can be coded immediately using Swift while the legacy Objective-C continues functioning as expected until it is fully rewritten.
Only use automated migration tools for syntax refactoring. Anything involving complex pointer memory management, macros and categories should be rewritten and migrated manually. Test coverage must hit at least 80% before you start the migration. Use code coverage reports to identify critical gaps before things get out of hand.
It is also important to schedule code reviews with mixed-experience teams because it helps mitigate subtle behavioral changes around optionals, safety and error handling patterns. Always expect API shifts and maintain an updated mapping between APIs at all times. The official Apple migration guide comes in handy at this stage.
Most importantly, set measurable milestones. Don’t embark on migration without a clear plan on what you want to achieve at every stage. Set clear timelines to achieve the milestones and keep communication lines with stakeholders open.
Summary
Migrating a codebase from Objective-C to Swift is typically a more complex challenge than it appears on the surface. Your team needs to be fully prepared and dedicated to achieving success. It is essential to evaluate different approaches at the start and create a comprehensive transition plan that combines the two languages in the most sustainable way.
The best part is that if you adhere to best practices, the final app you create will no longer carry Objective-C baggage. It will be a safe, high-performance, uncompromised Swift code designed with a Swift mindset to serve your needs.
Top comments (0)