Mock JSON · JSONEncoder · URLSession · Alamofire — 3 modes
Convert Swift to JSON
Mock data, encoder
snippets or patterns.
Generate mock JSON from a Swift struct, get
JSONEncoder
snippets for every scenario, or get URLSession and
Alamofire serialization patterns.
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Swift struct → mock JSON
JSONEncoder snippets
URLSession · Alamofire
Always free
Swift to JSON — 3 modes
100% client-side
Swift struct input
Ready
JSONEncoder vs JSONSerialization
Two Swift JSON encoding APIs — use JSONEncoder for all new code.
| JSONEncoder | JSONSerialization | |
|---|---|---|
| Input | Any Encodable type | Any (Dictionary, Array) |
| Type safety | Compile-time — type errors caught by Swift | Runtime — type casting required |
| Snake case | .keyEncodingStrategy = .convertToSnakeCase | Manual key mapping |
| Date format | .dateEncodingStrategy = .iso8601 | Manual ISO8601DateFormatter |
| Use for | All new Swift code with Codable models | Legacy ObjC codebases only |
Swift parsed in your
browser. No Xcode needed.
The mock JSON parser reads Swift struct property declarations — no Swift compiler, no Xcode. The snippets and patterns are generated from your selection — correct JSONEncoder API with encoding options, date strategies and key encoding strategies.
JSONEncoder options
outputFormatting, keyEncodingStrategy and dateEncodingStrategy — all three encoder options covered in the snippets.
URLSession async/await
Modern iOS 15+ pattern using async/await — not the closure-based URLSession.dataTask pattern from older tutorials.
Alamofire support
Alamofire's JSONParameterEncoder — the idiomatic way to send Codable structs as POST bodies in Alamofire 5+.
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Frequently asked questions
How do I convert a Swift struct to JSON?
Use JSONEncoder: let data = try JSONEncoder().encode(myStruct); let jsonString = String(data: data, encoding: .utf8). The struct must conform to Encodable or Codable. For pretty output: let encoder = JSONEncoder(); encoder.outputFormatting = .prettyPrinted; let data = try encoder.encode(myStruct).
How do I send a Swift Codable struct as a POST body?
Encode with JSONEncoder and set the request body: var request = URLRequest(url: url); request.httpMethod = "POST"; request.httpBody = try JSONEncoder().encode(myStruct); request.setValue("application/json", forHTTPHeaderField: "Content-Type"). Select the URLRequest scenario in the Snippets mode for the complete pattern with async/await.
How do I encode a Swift struct with snake_case JSON keys?
Set the keyEncodingStrategy on JSONEncoder: let encoder = JSONEncoder(); encoder.keyEncodingStrategy = .convertToSnakeCase; let data = try encoder.encode(myStruct). This automatically converts camelCase Swift property names to snake_case JSON keys — firstName becomes first_name, isActive becomes is_active.