SmartCodable - Resilient & Flexible Codable for Swift

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SmartCodable enhances Apple's native Codable with production-ready resilience. When standard Codable fails on a single missing field or type mismatch, your entire model is lost. SmartCodable gracefully recovers — falling back to defaults, converting types automatically, and never interrupting the parse.

Why SmartCodable?

Scenario	Standard Codable	SmartCodable
Missing key	❌ Throws keyNotFound, entire model fails	✅ Uses property initializer as default
Type mismatch (e.g., "123" for Int)	❌ Throws typeMismatch, entire model fails	✅ Auto-converts, returns 123
Null value for non-optional	❌ Throws valueNotFound, entire model fails	✅ Falls back to default value
Extra unknown keys	✅ Ignored	✅ Ignored

vs HandyJSON: SmartCodable builds on Apple's Codable protocol — no unsafe runtime reflection, no ABI stability risks. HandyJSON relies on Swift metadata reflection that may break across Swift versions.

vs Manual init(from:): SmartCodable eliminates the boilerplate of writing decodeIfPresent + ?? for every property. Same safety, zero ceremony.

Quick Start

import SmartCodable

struct User: SmartCodableX {
    var name: String = ""
    var age: Int = 0
}

// ✅ Normal case
let user = User.deserialize(from: ["name": "John", "age": 30])
// User(name: "John", age: 30)

// ✅ Missing field — falls back to default
let user2 = User.deserialize(from: ["name": "John"])
// User(name: "John", age: 0)

// ✅ Type mismatch — auto-converts
let user3 = User.deserialize(from: ["name": "John", "age": "30"])
// User(name: "John", age: 30)

To conform to SmartCodable, a class needs to implement an empty initializer:

class BasicTypes: SmartCodableX {
    var int: Int = 2
    var doubleOptional: Double?
    required init() {}
}
let model = BasicTypes.deserialize(from: json)

For struct, the compiler provides a default empty initializer:

struct BasicTypes: SmartCodableX {
    var int: Int = 2
    var doubleOptional: Double?
}
let model = BasicTypes.deserialize(from: json)

Installation

Swift Package Manager

dependencies: [
    .package(url: "https://github.com/iAmMccc/SmartCodable.git", branch: "main")
]

• SmartCodable provides the core parsing capabilities with no external dependencies.
• For class inheritance via @SmartSubclass, see the companion package SmartCodableMacro.

CocoaPods (legacy)

Starting from 7.0, SmartCodable no longer ships via CocoaPods. If you must stay on CocoaPods, please use the 6.x series, which is preserved on the 6.1.0 branch:

pod 'SmartCodable', '~> 6.1'

The 6.x line will receive critical fixes only. All new features will land in 7.x and beyond — we strongly recommend migrating to Swift Package Manager.

Features

1. Deserialization

Only types conforming to SmartCodable (or [SmartCodable] for arrays) can use these methods:

public static func deserialize(from dict: [String: Any]?, designatedPath: String? = nil, options: Set<SmartDecodingOption>? = nil) -> Self?

public static func deserialize(from json: String?, designatedPath: String? = nil, options: Set<SmartDecodingOption>? = nil) -> Self?

public static func deserialize(from data: Data?, designatedPath: String? = nil, options: Set<SmartDecodingOption>? = nil) -> Self?

public static func deserializePlist(from data: Data?, designatedPath: String? = nil, options: Set<SmartDecodingOption>? = nil) -> Self?

Multi-Format Input Support:

Input Type	Example Usage	Internal Conversion
Dictionary	Model.deserialize(from: dict)	Directly processes native collections
Array	[Model].deserialize(from: arr)	Directly processes native collections
JSON String	Model.deserialize(from: jsonString)	Converts to Data via UTF-8
Data	Model.deserialize(from: data)	Processes directly

Deep Path Navigation — Extract nested data directly:

// JSON: {"data": {"user": {"info": { ... }}}}
let model = Model.deserialize(from: json, designatedPath: "data.user.info")

Decoding Strategies:

let options: Set<SmartDecodingOption> = [
    .key(.convertFromSnakeCase),
    .date(.iso8601),
    .data(.base64)
]
let model = Model.deserialize(from: json, options: options)

Strategy Type	Available Options	Description
Key Decoding	.fromSnakeCase	snake_case → camelCase
	.firstLetterLower	"FirstName" → "firstName"
	.firstLetterUpper	"firstName" → "FirstName"
Date Decoding	.iso8601, .secondsSince1970, etc.	Full Codable date strategies
Data Decoding	.base64	Binary data processing
Float Decoding	.convertToString, .throw	NaN/∞ handling

⚠️ Important: Only one strategy per type is allowed (last one wins if duplicates exist)

2. Key Mapping

Map JSON keys to Swift property names. First non-null match wins:

static func mappingForKey() -> [SmartKeyTransformer]? {
    [
        CodingKeys.id <--- ["user_id", "userId", "id"],
        CodingKeys.name <--- "nested.path.to.name"   // nested path supported
    ]
}

3. Value Transformation

Convert between JSON values and custom types:

static func mappingForValue() -> [SmartValueTransformer]? {
    [
        CodingKeys.url <--- SmartURLTransformer(prefix: "https://"),
        CodingKeys.date <--- SmartDateFormatTransformer(DateFormatter()),
        CodingKeys.status <--- FastTransformer<Status, String>(
            fromJSON: { Status(rawValue: $0 ?? "") },
            toJSON: { $0?.rawValue }
        ),
    ]
}

Built-in Transformers:

Transformer	JSON → Object
SmartDateTransformer	Double/String → Date
SmartDateFormatTransformer	String (custom format) → Date
SmartDataTransformer	Base64 String → Data
SmartURLTransformer	String → URL (with optional prefix & encoding)
SmartHexColorTransformer	Hex String → UIColor/NSColor

Need custom logic? Implement ValueTransformable:

public protocol ValueTransformable {
    associatedtype Object
    associatedtype JSON
    func transformFromJSON(_ value: Any?) -> Object?
    func transformToJSON(_ value: Object?) -> JSON?
}

4. Property Wrappers

Wrapper	Purpose	Example
@SmartAny	Any, [Any], [String: Any] support	@SmartAny var dict: [String: Any] = [:]
@SmartIgnored	Skip property during decoding	@SmartIgnored var cache: String = ""
@SmartFlat	Flatten nested object into parent	@SmartFlat var profile: Profile?
@SmartPublished	Combine ObservableObject support	@SmartPublished var name: String?
@SmartHexColor	Hex string → UIColor/NSColor	@SmartHexColor var color: UIColor?
@SmartDate	Multi-format date parsing	@SmartDate var date: Date?
@SmartCompact.Array	Skip invalid array elements	@SmartCompact.Array var ids: [Int]
@SmartCompact.Dictionary	Skip invalid dict entries	@SmartCompact.Dictionary var info: [String: String]

@SmartAny example — support Any types that Codable can't handle natively:

struct Model: SmartCodableX {
    @SmartAny var dict: [String: Any] = [:]
    @SmartAny var arr: [Any] = []
    @SmartAny var any: Any?
}
let dict: [String: Any] = [
    "dict": ["name": "Lisa"],
    "arr": [1, 2, 3],
    "any": "Mccc"
]
let model = Model.deserialize(from: dict)
// Model(dict: ["name": "Lisa"], arr: [1, 2, 3], any: "Mccc")

@SmartIgnored example — skip property during decoding:

struct Model: SmartCodableX {
    @SmartIgnored
    var name: String = ""
}
let model = Model.deserialize(from: ["name": "Mccc"])
// Model(name: "")  — "name" was ignored, keeps default

@SmartFlat example — flatten nested fields into parent:

struct Model: SmartCodableX {
    var name: String = ""
    @SmartFlat var profile: Profile?
}
struct Profile: SmartCodableX {
    var name: String = ""
    var age: Int = 0
}

// JSON: {"name": "Mccc", "age": 18}
// profile gets name="Mccc", age=18 from the SAME level

@SmartCompact.Array example — tolerant array parsing:

struct Model: Decodable {
    @SmartCompact.Array var ages: [Int]
}

// JSON: {"ages": ["Tom", 1, {}, 2, 3, "4"]}
// Result: ages = [1, 2, 3, 4]  (invalid elements skipped, "4" auto-converted)

5. Inheritance

Class inheritance support has been moved to a separate package — SmartCodableMacro. It depends on swift-syntax, so we ship it independently to keep this core library lightweight and dependency-free.

Add it alongside SmartCodable when you need @SmartSubclass:

dependencies: [
    .package(url: "https://github.com/iAmMccc/SmartCodableMacro.git", branch: "main")
]

For inheritance usage on Swift versions prior to 5.9, see Inheritance in Lower Versions.

6. Enum Support

Simple enums — conform to SmartCaseDefaultable:

enum Sex: String, SmartCaseDefaultable {
    case man
    case woman
}

Enums with associated values — conform to SmartAssociatedEnumerable and provide a transformer via mappingForValue():

struct Model: SmartCodableX {
    var sex: Sex = .man
    static func mappingForValue() -> [SmartValueTransformer]? {
        [ CodingKeys.sex <--- SexTransformer() ]
    }
}

enum Sex: SmartAssociatedEnumerable {
    case man, woman, other(String)
}

struct SexTransformer: ValueTransformable {
    typealias Object = Sex
    typealias JSON = String
    func transformFromJSON(_ value: Any?) -> Sex? {
        guard let str = value as? String else { return nil }
        switch str {
        case "man": return .man
        case "woman": return .woman
        default: return .other(str)
        }
    }
    func transformToJSON(_ value: Sex?) -> String? { nil }
}

7. Post-Processing & Update

didFinishMapping() — runs after decoding completes:

struct Model: SmartCodableX {
    var name: String = ""
    mutating func didFinishMapping() {
        name = "I am \(name)"
    }
}

SmartUpdater — update an existing model with new data:

var model = Model.deserialize(from: initialData)!
SmartUpdater.update(&model, from: newData)

8. Compatibility

SmartCodable handles parsing failures gracefully, ensuring the entire model never fails:

let dict = ["number1": "123", "number2": "Mccc", "number3": "Mccc"]

struct Model: SmartCodableX {
    var number1: Int?
    var number2: Int?
    var number3: Int = 1
}
// Result: Model(number1: 123, number2: nil, number3: 1)

• Type conversion: "123" (String) → 123 (Int) automatically
• Default fill: When conversion fails, uses the property's initializer value (number3 = 1)
• Optional handling: When conversion fails for optionals, returns nil (number2 = nil)

Performance tip for large data: When parsing very large datasets, avoid unnecessary compatibility overhead — use CodingKeys to exclude unused properties instead of @SmartIgnored, as it's more efficient.

9. Stringified JSON

SmartCodable auto-detects and parses string-encoded JSON:

struct Model: SmartCodableX {
    var hobby: Hobby?
}
// JSON: {"hobby": "{\"name\":\"sleep\"}"}
// hobby is parsed as Hobby(name: "sleep"), not a raw string

10. Debugging

SmartSentinel.debugMode = .verbose  // .none | .verbose | .alert
SmartSentinel.onLogGenerated { log in print(log) }

================================  [Smart Sentinel]  ================================
UserModel 👈🏻 👀
╆━ UserModel
┆┄ age    : Expected Int, got String — auto-converted
┆┄ email  : Key not found — using default ""
====================================================================================

Explore & Contribute

🔧 Migrate from HandyJSON	Step-by-step migration guide
🛠 SmartModeler	JSON → SmartCodable model generator
👀 SmartSentinel	Real-time parsing log viewer
💖 Contributing	Support SmartCodable development
🏆 Contributors	Key contributors

FAQ

• 👉 Learn more about SmartCodable
• 👉 GitHub Discussions
• 👉 How to Test

GitHub Stars

Join Community 🚀

SmartCodable is an open-source project dedicated to making Swift data parsing more robust, flexible and efficient. We welcome all developers to join our community!