Fosutilities API Catalog

FOSUtilities API Catalog

Before hand-writing a helper in a project that imports these libraries, check whether it already exists. Fifteen-plus years of accumulated API lives here; the most common failure is reinventing it.

How to use this skill

1. Find your reach in the index below.
2. Read only the catalog file(s) it points to, from ../shared/api-catalog/.
3. Prefer the catalogued API over hand-rolled code; use it as the entry shows (each entry's example is the idiomatic form).

If your reach isn't in the index, scan the catalog file for the library you're importing — and if the capability exists but the index line was missing, add the line via the fosutilities-api-catalog-update skill.

Reach-for index

• Reaching for JSONEncoder/JSONDecoder, writing Codable glue → FOSFoundation.md § Coding
• Reaching for DateFormatter/ISO8601DateFormatter for wire or JSON dates → FOSFoundation.md § Coding
• Building stub/test instances of Codable types → FOSFoundation.md § Coding, FOSTesting.md § FOSTesting
• Reaching for URLSession/URLRequest, fetching or posting Codable data → FOSFoundation.md § Networking
• Reaching for URLSessionWebSocketTask → FOSFoundation.md § Networking
• Mocking network calls in tests → FOSFoundation.md § Networking, FOSTesting.md § FOSTesting
• Grouping an array into a dictionary, or rate-limiting (throttling) iteration → FOSFoundation.md § Collections
• Converting string casing (camel/snake), trimming prefixes/suffixes, generating random strings → FOSFoundation.md § String
• Hashing (SHA-256/HMAC), obfuscating strings, parsing hex strings or CSV files → FOSFoundation.md § String
• Rounding doubles, or formatting integers as hex → FOSFoundation.md § Numbers
• Comparing or parsing app/API versions (semver) → FOSFoundation.md § Versioning
• Reaching for semaphores in async code, or calling async code from a sync context → FOSFoundation.md § Async
• Detecting simulator/TestFlight installs, reading the app bundle's version → FOSFoundation.md § Extensions
• Typing a model identifier (never a raw UUID/String field) → FOSFoundation.md § Data
• Declaring a ViewModel or versioning its factory (@ViewModel, @VersionedFactory) → FOSMVVM.md § Macros
• Localizing properties from YAML (@LocalizedString), substituting values into localized text → FOSMVVM.md § Localization
• Encoding a ViewModel with its localizations resolved → FOSMVVM.md § Extensions
• Describing form fields — control type, keyboard, input constraints, value binding → FOSMVVM.md § Forms
• Validating user input, reporting and aggregating validation outcomes → FOSMVVM.md § Validation
• Binding a screen to server data — ViewModel requests, CRUD writes, factories → FOSMVVM.md § Protocols
• Identifying which entity a model is (opaque ModelIdentity) — keying refresh or authorization by it → FOSMVVM.md § Protocols
• Container-scoped authorization — declaring containers, grant verbs, who may touch which records → FOSMVVM.md § Protocols
• Client-chosen sort or pagination on a request → FOSMVVM.md § Protocols
• Live-updating screens that refresh when server data changes (@ViewModel(options: [.live])), or replacing the invalidation transport → FOSMVVM.md § Protocols, FOSMVVMVapor.md § Live Invalidation
• Attaching auth headers (bearer token, API key) to every client request, rotation-safe — or recovering when the server refuses one (refresh the credential and retry the request once) → FOSMVVM.md § Protocols
• Declaring the data a server-rendered body needs — composable factory, load requirements, rooted scopes → FOSMVVM.md § Protocols
• Rendering a ViewModel in SwiftUI — app setup, view binding, previews, form views → FOSMVVM.md § SwiftUI Support
• A Button whose action is async throws — error routing, re-entry refusal, running state, tap-to-cancel → FOSMVVM.md § SwiftUI Support
• A view-lifetime (or value-keyed) load that can throw — .task-style error routing into the screen binding → FOSMVVM.md § SwiftUI Support
• Showing errors to the user — localized error messages on error types, one alert fed by a shared error binding → FOSMVVM.md § Protocols, § SwiftUI Support
• Versioning ViewModel properties, choosing deployment URLs, negotiating versions over HTTP → FOSMVVM.md § Versioning
• Booting a Vapor server for MVVM — YAML localization store, environment, locale, Leaf rendering → FOSMVVMVapor.md § Extensions
• Registering request routes (reads and CRUD writes) — including mounting one behind a credential/middleware group — or serving a request outside the guarded verbs → FOSMVVMVapor.md § Vapor Support
• Projecting loaded records into a response body, or reading them through the projection context → FOSMVVMVapor.md § Containment, § Protocols
• Declaring Fluent containers and their relations, or mapping sort meanings to database columns → FOSMVVMVapor.md § Containment
• Registering the container authorization provider, apex resolver, per-request app state, or a container migration → FOSMVVMVapor.md § Containment, § Extensions
• Filtering (narrowing) a large container load by the request's query → FOSMVVMVapor.md § Containment
• Enabling server-pushed refresh at boot, or transactional writes that notify live clients → FOSMVVMVapor.md § Live Invalidation
• Refreshing live screens whose data isn't Fluent-persisted — nudging from an Application-hosted actor or computed aggregate, or registering a dependency the load plan can't see → FOSMVVMVapor.md § Live Invalidation
• The server-side write path — candidate set, field application, authorization provider → FOSMVVMVapor.md § Protocols
• Projecting the database into ViewModels — resolvable requests, Fluent DataModel → FOSMVVMVapor.md § Protocols
• Serving typed/localized errors, gating routes on client app version → FOSMVVMVapor.md § Middleware
• Verifying a caller's bearer token / protecting route groups with app-owned credential rules → FOSMVVMVapor.md § Middleware
• Testing ViewModels — Codable round-trip, version stability, translation coverage → FOSTesting.md § FOSTesting
• UI-testing SwiftUI ViewModel views (XCUITest hosting, operations, identifiers, keyboard dismissal) → FOSTesting.md § FOSTestingUI, FOSMVVM.md § SwiftUI Support
• Testing Vapor ServerRequests end to end, or Fluent-backed code against a fresh in-memory database → FOSTesting.md § FOSTestingVapor
• Testing a streaming / SSE endpoint over a real socket → FOSTesting.md § FOSTestingVapor
• Generating PDFs from SwiftUI views, choosing page size/orientation → FOSReporting.md § PDF Rendering