Swift generics interview questions

Generics questions separate people who memorized syntax from people who design reusable APIs. Interviewers want to see judgment about when abstraction pays off.

What gets asked

Expect writing a generic function or type, adding constraints with where clauses, and explaining associated types in protocols. A frequent comparison is generics versus using a protocol as a type, and interviewers may ask you to refactor duplicated code into a single generic implementation while keeping it readable.

Showing design judgment

Explain that generics let you write one implementation that stays type safe across many concrete types, with constraints expressing exactly what capabilities you require. Balance that against readability: over-generic code is hard to follow, so reach for generics when you have real duplication or a library boundary, not to show off.

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Share Your Screen works topics like this through in full: 75 solved Swift problems with tests, 9 real case studies, and 7 annotated mock interviews, so you rehearse the live round instead of just reading about it.

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Frequently asked

What is the difference between generics and using a protocol as a type?

Generics preserve the concrete type and are resolved at compile time with full type safety; an existential protocol type erases it and adds runtime indirection. Prefer generics for hot paths.

What are associated types?

Placeholders in a protocol that a conforming type fills in, letting the protocol describe a family of related types, as Collection does with Element.