A2ui Swift Development

Swift development skill

This skill guides AI agents and contributors working in the swift/ directory. It outlines target boundaries, coding standards, testing patterns, and mandatory verification steps.

1. Specification and blueprint grounding

Before modifying or implementing Swift code, inspect the authoritative specifications:

• Protocol envelopes and schemas: specification/v0_9_1/json/ defines wire-format types and validation schemas.
• Component catalog schema: basic/catalog.json defines components, properties, and function signatures.
• Core module blueprint: a2ui_core.blueprint.md specifies state handling, JSON pointer rules, auto-vivification, and error semantics.
• Framework adapter blueprint: a2ui_framework_adapter.blueprint.md specifies view mapping, reactive subscription lifecycles, and layout behavior.
• Reference implementation: renderers/web_core/ serves as the canonical behavioral reference for edge-case resolution.

2. Swift target architecture

The Swift implementation uses targets defined in root Package.swift:

• A2UIJSON (core/Sources/A2UIJSON): Pure JSON Schema 2020-12 definitions and remote schema registry storage.
• A2UICore (core/Sources/A2UICore): Stateful runtime engine managing MessageProcessor, DataModel, SurfaceGroupModel, pointer evaluation, and action routing.
• BasicCatalog (core/Sources/BasicCatalog): Core schema definitions and function handlers for Basic Catalog components.
• A2UISwiftUI (swiftui/Sources/A2UISwiftUI): SwiftUI adapter providing the root Surface view, recursive ComponentNodeView, and environment keys.
• BasicCatalogSwiftUI (swiftui/Sources/BasicCatalog): Concrete SwiftUI view implementations conforming to ComponentImplementation.
• A2UISampleClient (swift/sample): Interactive iOS Gallery application managed via Xcode project file.

3. Mandatory coding standards

All Swift code must strictly follow swift/CODING_STANDARDS.md and the Google Swift Style Guide:

1. One primary type per file: Every class, struct, enum, and protocol must live in a dedicated file named after the type.
2. 100-character line limit: No line of code, comment, docstring, or markdown may exceed 100 characters.
3. 2-space indentation: Enforced by swift-format.
4. Apache 2.0 copyright header: Required on every new .swift file:

   // Copyright 2024 Google LLC
   //
   // Licensed under the Apache License, Version 2.0 (the "License");
   // you may not use this file except in compliance with the License.
   // You may obtain a copy of the License at
   //
   //     https://www.apache.org/licenses/LICENSE-2.0
   //
   // Unless required by applicable law or agreed to in writing, software
   // distributed under the License is distributed on an "AS IS" BASIS,
   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   // See the License for the specific language governing permissions and
   // limitations under the License.
   

5. Safe optional handling: Never use force-unwrapping (!) or forced tries (try!). Use optional bindings (if let, guard let) or propagate throwing errors.

4. Swift Testing conventions

Tests use the native Swift Testing framework:

• Import Testing instead of XCTest.
• Annotate test functions with @Test.
• Use #expect(...) for assertions.
• In tests, replace force unwraps with try #require(...) to produce clean test failures instead of crashes.
• Avoid @testable import. Test only the public API surface.
• Use standard camelCase identifiers for test function names without backticks or spaces.

5. Verification workflow

After making any code changes in swift/, run this verification sequence from the repository root:

1. Auto-format code:

   swift-format format -i -r Package.swift swift/
   

2. Lint check:

   swift-format lint -r Package.swift swift/
   

3. Run unit tests:

   swift test
   

   Or run filtered tests during iterative development:

   swift test --filter A2UICoreTests
   swift test --filter A2UISwiftUITests
   

4. Compile check:

   swift build
   

6. Integration with repository skills

• Blueprint compliance: When updating models or schemas, check compliance with a2ui-blueprint-compliance.
• Test quality: Verify assertion strength and boundary cases with a2ui-test-quality-check.
• Documentation sync: Ensure documentation reflects code changes using a2ui-doc-sync-check.