Agent-skills-standard swift-error-handling

Standards for throwing functions, Result type, and Never. Use when implementing Swift error throwing, designing error hierarchies, using Result types, or adding do-catch blocks. (triggers: **/*.swift, throws, try, catch, Result, Error)

install

source · Clone the upstream repo

git clone https://github.com/HoangNguyen0403/agent-skills-standard

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/HoangNguyen0403/agent-skills-standard "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/swift/swift-error-handling" ~/.claude/skills/hoangnguyen0403-agent-skills-standard-swift-error-handling && rm -rf "$T"

manifest: skills/swift/swift-error-handling/SKILL.md

source content

Swift Error Handling

Priority: P0

Workflow: Add Error Handling to Swift Function

Define custom error enum conforming to
```
Error
```
Mark function
```
throws
```
(or
```
async throws
```
)
Use
```
do-catch
```
at call site with specific catch clauses
Map domain errors to user-facing messages at presentation layer

Implementation Guidelines

Throwing Functions

Propagate Errors: Use
```
throws
```
for recoverable errors and
```
async throws
```
for modern concurrency.
Do-Catch: Handle close to source; specific catch clauses per error type. Catch-all
```
catch
```
: last resort.
Error Types: Define custom errors as enums conforming to
```
Error
```
:

See implementation examples for custom error enums, do-catch patterns, and Result type usage.

Optional Try: Use
```
try?
```
only for non-critical errors where nil acceptable.

Result Type

Async Alternatives: Use
```
throws
```
for synchronous code. Use
```
Result
```
for callbacks and non-async deferred error states.
Transformations: Use
```
.map()
```
,
```
.flatMap()
```
for functional composition.
Conversion: Use
```
.get()
```
to convert
```
Result
```
to throwing for use in
```
try-catch
```
.

Never Type & Preconditions

Fatalisms: Use
```
Never
```
return type only for unrecoverable crash scenarios or to indicate unreachable code. Never for expected errors.
Preconditions: Use
```
precondition()
```
,
```
assert()
```
, and
```
fatalError()
```
for programmer errors. Use
```
assertionFailure()
```
for debug-only checks.

Anti-Patterns

No try!: Use
```
try?
```
or
```
do-catch
```
.
No try? without nil check: Handle or log.
No Error(message): Use typed errors.

References

Error Types & Result