# Foundation

> Route Swift Foundation framework implementation tasks to the correct Knowledge Contracts -- date/time formatting, measurement and unit formatting, Codable encoding and custom conformance, and FileManager app sandbox directories. Use when working with DateFormatter, ISO8601DateFormatter, Date.FormatStyle, .formatted(), RelativeDateTimeFormatter, Measurement, .converted(to:), MeasurementFormatter, unitStyle, unitOptions, JSONEncoder, Codable, encode(to:), init(from:), CodingKeys, FileManager, Documents directory, Caches directory, Application Support directory, or isExcludedFromBackup. v1 is a curated, highest-usage subset of Foundation -- not an exhaustive API reference.

- Skill: `caglarbaranbora/foundation` (Agent Skill)
- Install (CLI): `npx skillmds@latest add caglarbaranbora/foundation`
- Raw SKILL.md: https://api.skillmd.com/api/skills/caglarbaranbora/foundation/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: caglarbaranbora (https://skillmd.com/u/caglarbaranbora)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/caglarbaranbora/foundation

---


# Foundation — Foundations Skill

## Purpose

Route Swift Foundation framework implementation tasks to the minimum
required Foundation Knowledge Contracts. v1 scope is a deliberately
curated, highest-usage subset of four topics — not an exhaustive
Foundation API reference.

## Routing

Load only the contracts relevant to the task. All paths relative to
knowledge/foundation/.

-   `DateFormatter`, `ISO8601DateFormatter`, `Date.FormatStyle`,
    `.formatted()`, `RelativeDateTimeFormatter`, or formatter-reuse
    performance -> date-time-formatting.md
-   `Measurement`, `.converted(to:)`, `MeasurementFormatter`, `unitStyle`,
    or `unitOptions` -> measurement-and-unit-formatting.md
-   `JSONEncoder`, custom `encode(to:)`/`init(from:)` conformance, or
    `CodingKeys` for encoding -> codable-encoding-and-custom-conformance.md
-   `FileManager`, `Documents`/`Caches`/`Application Support` directories,
    safe file read/write, or `isExcludedFromBackup` ->
    filemanager-app-sandbox-directories.md

Never load more than the contracts relevant to the specific question.

## Stop Conditions

Stop and report if the requested topic has no matching Knowledge Contract
in knowledge/foundation/ — do not guess or fall back to general knowledge.

-   Unit-of-measure copy wording (spelling out vs. abbreviating, spacing,
    capitalization once a value is already display text) — owned by
    `style-guide`.
-   Network-response `Codable` decoding (`JSONDecoder`, `DecodingError`
    handling for fetched data) — owned by `networking`.
-   General String/Unicode text processing, `NotificationCenter`, the
    `Result` type, and GCD/`DispatchQueue` — Deferred; no domain owns them yet.
-   Locale/Bundle localization and translation workflow mechanics — owned by
    `localization`.
-   Combine — owned by `combine`.