What Combine is for

Combine Junior Swift 5.1+ iOS 13+ Reviewed 31 Oct 2026 By Alok Singh

Pick the fix

Which task suits Combine best?

OptionsEnable a Sign Up button only when the email, password and terms fields are all valid, updating liveLoad a user profile once when a screen opensWrite a file to diskSort an array

Hint 1 of 1

Which option has several values changing over time?

Choose an answer, then open Show answer below to check it.

Show answer

Answer: A Enable a Sign Up button only when the email, password and terms fields are all valid, updating live

Correct. Combining several streams of values over time is Combine's strength.

Why not the others?

B Load a user profile once when a screen opens. One-shot work reads better with async/await.
C Write a file to disk. Synchronous or async file I/O doesn't need a stream.
D Sort an array. That is a plain synchronous call.

30-second answer

Combine is Apple's framework for values that change over time. Publishers emit values, operators transform and combine them, and subscribers receive them, with cancellation built in. It shines when several streams must be combined, like form validation or search, and it powers ObservableObject's @Published. For one-shot async work, async/await is now simpler.

Practise saying it · 30 s. No recording, just a timer

Explain what Combine is for.

Say your answer out loud, then check which of these points you covered:

Values over time
Publishers, operators, subscribers
Where async/await is simpler

Deep dive

Combine is available from iOS 13 and is still supported, but most new APIs favour async sequences and Observation.

Publishers are declarative: nothing runs until something subscribes.

Back-pressure is handled through demand from subscribers.

publisher.values bridges a publisher to an AsyncSequence.

Common mistakes

Using Combine for one network call.
Forgetting nothing happens without a subscriber.

Senior take & follow-ups

Seniors place Combine in today's toolset instead of defending or dismissing it.

Follow-up questions

Think of your answer first, then open the hint.

Is Combine deprecated?
Show hint
No, but Observation and async/await cover many of its old uses.
How do you use a publisher from async code?
Show hint
for await value in publisher.values.

Suggest a fix if something here is wrong or out of date.