Using JSON with custom types

At a glance

Project structure

Source bundle/
└── Using-JSON-with-Custom-Types.playground/
    └── Pages/
        ├── Access Nested Data.xcplaygroundpage/
        │   └── Contents.swift
        ├── Merge Data from Different Depths.xcplaygroundpage/
        │   └── Contents.swift
        ├── Change Key Names.xcplaygroundpage/
        │   └── Contents.swift
        ├── Read Data from Arrays.xcplaygroundpage/
        │   └── Contents.swift
        ├── LICENSE.xcplaygroundpage/
        │   └── Contents.swift
        └── Table of Contents.xcplaygroundpage/
            └── Contents.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 0 project/configuration file(s) and 10 source declaration(s).

Overall architecture

flowchart LR
    N1["GroceryStore"]
    N2["GroceryStoreService"]
    N3["Foundation APIs"]
    N1 --> N2
    N2 --> N3

Reference code

Using-JSON-with-Custom-Types.playground/Pages/Access Nested Data.xcplaygroundpage/Contents.swift:34 — architecture anchor

struct GroceryStore {
    var name: String
    var products: [Product]

    struct Product: Codable {
        var name: String
        var points: Int
        var description: String?
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into Foundation.

Ownership and state

classDiagram
    GroceryStore *-- String : name
    GroceryStore *-- Array : products
    Product *-- String : name
    Product *-- Int : points

Ownership evidence

Using-JSON-with-Custom-Types.playground/Pages/Access Nested Data.xcplaygroundpage/Contents.swift:35 — stored dependency or nearest verified ownership anchor

struct GroceryStore {
    var name: String
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

Using-JSON-with-Custom-Types.playground/Pages/Access Nested Data.xcplaygroundpage/Contents.swift:34 — representative type boundary

struct GroceryStore {
    var name: String
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

Using-JSON-with-Custom-Types.playground/Pages/Merge Data from Different Depths.xcplaygroundpage/Contents.swift:124 — representative boundary

    public init(from decoder: Decoder) throws {
        var products = [Product]()
        // ...
    }

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: Service: GroceryStoreService; Store: GroceryStore.
• Protocols: no local protocol declaration in the scanned source.
• Methods: encode.
• Files: feature/project roles rather than a strict one-type-per-file rule.

Architecture takeaways

• GroceryStore is the main source-visible entry or composition anchor for this sample.
• Framework work reaches Foundation through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation