Swift Academy · Lesson

map and flatMap on Result

Chaining transformations on success values without nested switch statements.

Lesson 2 of 412 steps

map and flatMap on Result is a free Swift Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 4 lessons in total.

Welcome

`map` and `flatMap` on `Result` let you transform success values without nested switch statements, keeping your code flat and readable.

map on Result

```swift let r: Result = .success(5) let doubled = r.map { $0 * 2 } // .success(10) let failed: Result = .failure(MyError.bad) let same = failed.map { $0 * 2 } // .failure(MyError.bad) ```

mapError on Result

```swift let r: Result = .failure(URLError(.notConnectedToInternet)) let mapped = r.mapError { AppError.network($0) } // Result ```

flatMap — Chaining Fallible Operations

```swift func parseJSON(_ data: Data) -> Result { ... } func validate(_ user: User) -> Result { ... } let result: Result = fetchResult .flatMap { parseJSON($0) } .flatMap { validate($0).mapError { $0 as Error } } ```

flatMapError

```swift func recover(_ e: NetworkError) -> Result { .success(cachedData) } let result = networkResult.flatMapError { recover($0) } ```

map vs flatMap on Result

• `map`: transforms the success value; if the transform returns `T`, result is `Result` • `flatMap`: transform returns `Result`; prevents nesting `Result,E>`

Chaining Three Operations

```swift fetchData(url) .map { parse($0) } .flatMap { validate($0) } .map { transform($0) } // Each step only runs if previous succeeded ```

Comparison to Optional Chaining

Result chaining is like optional chaining for errors: ```swift // Optional chain: name?.uppercased()?.prefix(5) // Result chain: result.map { $0.uppercased() }.map { $0.prefix(5) } ```

Converting to Optional

```swift let opt = result.success // Value? — nil on failure let val = try? result.get() // Value? — nil on failure ```

Recovering with ??-like Pattern

```swift let value = (try? result.get()) ?? defaultValue ```

Quick Check

What does `result.flatMap { transform($0) }` do when `result` is `.failure`?

Answer it in the interactive lesson

Recap

Key takeaways: • `map` transforms success, passes failure through • `mapError` transforms the failure type • `flatMap` chains operations that themselves return Result • Avoids nested switch statements • Chain for clean error-propagating pipelines Next: custom error types.

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Frequently Asked Questions

Is the “map and flatMap on Result” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “map and flatMap on Result”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 4 lessons in total.

What will I learn in “map and flatMap on Result”?

Chaining transformations on success values without nested switch statements. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Swift Academy?

No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “map and flatMap on Result” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

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