java-to-swift
Skill1 starsChanged 3 months agoMITView on GitHub
Use when converting Java 1.8 classes to Swift 5.0+ Codable structs - handling type mapping, nullability, inheritance flattening, BaseReq exclusions, and property naming conventions.
In this repository13 other files it gives its agents.
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The file
We split this skill into the rules it gives an agent
9 rules. About 0 are common, 6 are distinctive, and 3 are very specific to this project.
≈0
Common · estimate
Many files like this have a rule of this kind.
≈6
Distinctive · estimate
This author's own choices. Worth a look.
3
Very specific
Tied to their project's names, files or tools. Probably skip.
- Common
- Distinctive
- Very specific
- Distinctive: line 40
Default: All properties are optional unless explicitly marked non-null.
- Distinctive: line 65
Document property source with inline comments
- Distinctive: line 83
Place comments immediately above each property
- Distinctive: line 88
All converted structs must:
- Very specific: line 91
Use let for all properties (immutable)
- Distinctive: line 97
If inheritance detected → request/read parent class files
- Very specific: line 99
Create Swift struct with Codable conformance
- Very specific: line 102
Use let for all properties
- Distinctive: line 103
Keep property names identical to Java/server-side
≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.
Files
Java to Swift Conversion
Overview
Converts Java 1.8 classes to Swift 5.0+ struct objects conforming to Codable. Output as markdown code blocks only — never modify project files.
Core Constraint
CRITICAL: Output Swift struct definitions as markdown code blocks only. Do NOT modify, edit, or alter any project files.
Type Mapping
| Java Type | Swift Type |
int / Integer | Int |
long / Long | Int64 |
float / Float | Float |
double / Double | Double |
boolean / Boolean | Bool |
String | String |
BigDecimal / decimal | Double (default) or String (with @BigDecimalToString) |
Date | Date |
Timestamp | TimeInterval |
List<T> | [T] |
Map<K,V> | [K: V] |
Nullability Rules
| Java Annotation | Swift Type |
@NonNull / @NotNull | Non-optional (String) |
No annotation / @Nullable | Optional (String?) |
Default: All properties are optional unless explicitly marked non-null.
Naming Conventions
Struct names: PascalCase (OrderDetails, UserProfile, PaymentRequest)
Property names: ⚠️ KEEP IDENTICAL TO JAVA/SERVER-SIDE — preserves Codable serialization.
// ✅ Correct
struct OrderRequest: Codable {
let orderId: String // matches Java field name
let total_amount: String? // preserves snake_case
}Swift's Codable maps property names directly to JSON keys — changing names breaks serialization.
Inheritance Handling
Swift structs don't support inheritance. Always flatten the hierarchy:
- Trace full inheritance chain — read all parent class files
- If any parent is
BaseReq→ EXCLUDE allBaseReqproperties (handled by network layer) - Combine all remaining properties from parent + child into one struct
- Document property source with inline comments
struct OrderRequest: Codable {
// From ApiRequest
let userId: String
// From OrderRequest
let orderId: Int64
// Note: BaseReq properties (token, timestamp) excluded — handled by network layer
}Documentation
Migrate Java comments to Swift using /// triple-slash format:
- Preserve original language (Chinese stays Chinese, English stays English)
- Place comments immediately above each property
- For properties without Java comments, add brief descriptive comment
Structure Requirements
All converted structs must:
- Be defined as
struct(notclass) - Conform to
Codableprotocol - Use
letfor all properties (immutable) - Flatten all inherited properties into a single struct
Step-by-Step Workflow
- Analyze Java class — properties, annotations, types, inheritance
- If inheritance detected → request/read parent class files
- Handle
BaseReqexclusion if applicable - Create Swift struct with
Codableconformance - Apply type mapping (including
@BigDecimalToString) - Apply nullability (
@NonNull→ non-optional, else optional) - Use
letfor all properties - Keep property names identical to Java/server-side
- Migrate comments with
///preserving original language
Validation Checklist
@NonNull/@NotNullproperties are non-optional- All other properties are optional (
?) - Struct conforms to
Codable - All properties use
let - Inheritance detected and parent classes analyzed
- All inherited properties flattened into single struct
BaseReqproperties excluded if applicable- Property names identical to server-side model
- Output is markdown code block only (no file modifications)
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