HandyJSON: a framework written in Swift which to make converting model objects to and from JSON easy on iOS

by iOS Example

HandyJSON

To deal with crash on iOS 15 beta3 please try version 5.0.4-beta

HandyJSON is a framework written in Swift which to make converting model objects( pure classes/structs ) to and from JSON easy on iOS.

Compared with others, the most significant feature of HandyJSON is that it does not require the objects inherit from NSObject(not using KVC but reflection), neither implements a 'mapping' function(writing value to memory directly to achieve property assignment).

HandyJSON is totally depend on the memory layout rules infered from Swift runtime code. We are watching it and will follow every bit if it changes.

Sample Code

Deserialization

class BasicTypes: HandyJSON {
    var int: Int = 2
    var doubleOptional: Double?
    var stringImplicitlyUnwrapped: String!

    required init() {}
}

let jsonString = "{\"doubleOptional\":1.1,\"stringImplicitlyUnwrapped\":\"hello\",\"int\":1}"
if let object = BasicTypes.deserialize(from: jsonString) {
    print(object.int)
    print(object.doubleOptional!)
    print(object.stringImplicitlyUnwrapped)
}

Serialization


let object = BasicTypes()
object.int = 1
object.doubleOptional = 1.1
object.stringImplicitlyUnwrapped = “hello"

print(object.toJSON()!) // serialize to dictionary
print(object.toJSONString()!) // serialize to JSON string
print(object.toJSONString(prettyPrint: true)!) // serialize to pretty JSON string

Features

  • Serialize/Deserialize Object/JSON to/From JSON/Object

  • Naturally use object property name for mapping, no need to specify a mapping relationship

  • Support almost all types in Swift, including enum

  • Support struct

  • Custom transformations

  • Type-Adaption, such as string json field maps to int property, int json field maps to string property

An overview of types supported can be found at file: BasicTypes.swift

Requirements

  • iOS 8.0+/OSX 10.9+/watchOS 2.0+/tvOS 9.0+

  • Swift 3.0+ / Swift 4.0+ / Swift 5.0+

Installation

To use with Swift 5.0/5.1 ( Xcode 10.2+/11.0+ ), version == 5.0.2

To use with Swift 4.2 ( Xcode 10 ), version == 4.2.0

To use with Swift 4.0, version >= 4.1.1

To use with Swift 3.x, version >= 1.8.0

For Legacy Swift2.x support, take a look at the swift2 branch.

Cocoapods

Add the following line to your Podfile:

pod 'HandyJSON', '~> 5.0.2'

Then, run the following command:

$ pod install

Carthage

You can add a dependency on HandyJSON by adding the following line to your Cartfile:

github "alibaba/HandyJSON" ~> 5.0.2

Manually

You can integrate HandyJSON into your project manually by doing the following steps:

  • Open up Terminal, cd into your top-level project directory, and add HandyJSON as a submodule:
git init && git submodule add https://github.com/alibaba/HandyJSON.git

  • Open the new HandyJSON folder, drag the HandyJSON.xcodeproj into the Project Navigator of your project.

  • Select your application project in the Project Navigator, open the General panel in the right window.

  • Click on the + button under the Embedded Binaries section.

  • You will see two different HandyJSON.xcodeproj folders each with four different versions of the HandyJSON.framework nested inside a Products folder.

It does not matter which Products folder you choose from, but it does matter which HandyJSON.framework you choose.

  • Select one of the four HandyJSON.framework which matches the platform your Application should run on.

  • Congratulations!

Deserialization

The Basics

To support deserialization from JSON, a class/struct need to conform to 'HandyJSON' protocol. It's truly protocol, not some class inherited from NSObject.

To conform to 'HandyJSON', a class need to implement an empty initializer.

class BasicTypes: HandyJSON {
    var int: Int = 2
    var doubleOptional: Double?
    var stringImplicitlyUnwrapped: String!

    required init() {}
}

let jsonString = "{\"doubleOptional\":1.1,\"stringImplicitlyUnwrapped\":\"hello\",\"int\":1}"
if let object = BasicTypes.deserialize(from: jsonString) {
    // …
}

Support Struct

For struct, since the compiler provide a default empty initializer, we use it for free.

struct BasicTypes: HandyJSON {
    var int: Int = 2
    var doubleOptional: Double?
    var stringImplicitlyUnwrapped: String!
}

let jsonString = "{\"doubleOptional\":1.1,\"stringImplicitlyUnwrapped\":\"hello\",\"int\":1}"
if let object = BasicTypes.deserialize(from: jsonString) {
    // …
}

But also notice that, if you have a designated initializer to override the default one in the struct, you should explicitly declare an empty one(no required modifier need).

Support Enum Property

To be convertable, An enum must conform to HandyJSONEnum protocol. Nothing special need to do now.

enum AnimalType: String, HandyJSONEnum {
    case Cat = "cat"
    case Dog = "dog"
    case Bird = "bird"
}

struct Animal: HandyJSON {
    var name: String?
    var type: AnimalType?
}

let jsonString = "{\"type\":\"cat\",\"name\":\"Tom\"}"
if let animal = Animal.deserialize(from: jsonString) {
    print(animal.type?.rawValue)
}

Optional/ImplicitlyUnwrappedOptional/Collections/...

'HandyJSON' support classes/structs composed of optional, implicitlyUnwrappedOptional, array, dictionary, objective-c base type, nested type etc. properties.

class BasicTypes: HandyJSON {
    var bool: Bool = true
    var intOptional: Int?
    var doubleImplicitlyUnwrapped: Double!
    var anyObjectOptional: Any?

    var arrayInt: Array<Int> = []
    var arrayStringOptional: Array<String>?
    var setInt: Set<Int>?
    var dictAnyObject: Dictionary<String, Any> = [:]

    var nsNumber = 2
    var nsString: NSString?

    required init() {}
}

let object = BasicTypes()
object.intOptional = 1
object.doubleImplicitlyUnwrapped = 1.1
object.anyObjectOptional = "StringValue"
object.arrayInt = [1, 2]
object.arrayStringOptional = ["a", "b"]
object.setInt = [1, 2]
object.dictAnyObject = ["key1": 1, "key2": "stringValue"]
object.nsNumber = 2
object.nsString = "nsStringValue"

let jsonString = object.toJSONString()!

if let object = BasicTypes.deserialize(from: jsonString) {
    // ...
}

Designated Path

HandyJSON supports deserialization from designated path of JSON.

class Cat: HandyJSON {
    var id: Int64!
    var name: String!

    required init() {}
}

let jsonString = "{\"code\":200,\"msg\":\"success\",\"data\":{\"cat\":{\"id\":12345,\"name\":\"Kitty\"}}}"

if let cat = Cat.deserialize(from: jsonString, designatedPath: "data.cat") {
    print(cat.name)
}

Composition Object

Notice that all the properties of a class/struct need to deserialized should be type conformed to HandyJSON.

class Component: HandyJSON {
    var aInt: Int?
    var aString: String?

    required init() {}
}

class Composition: HandyJSON {
    var aInt: Int?
    var comp1: Component?
    var comp2: Component?

    required init() {}
}

let jsonString = "{\"num\":12345,\"comp1\":{\"aInt\":1,\"aString\":\"aaaaa\"},\"comp2\":{\"aInt\":2,\"aString\":\"bbbbb\"}}"

if let composition = Composition.deserialize(from: jsonString) {
    print(composition)
}

Inheritance Object

A subclass need deserialization, it's superclass need to conform to HandyJSON.

class Animal: HandyJSON {
    var id: Int?
    var color: String?

    required init() {}
}

class Cat: Animal {
    var name: String?

    required init() {}
}

let jsonString = "{\"id\":12345,\"color\":\"black\",\"name\":\"cat\"}"

if let cat = Cat.deserialize(from: jsonString) {
    print(cat)
}

JSON Array

If the first level of a JSON text is an array, we turn it to objects array.

class Cat: HandyJSON {
    var name: String?
    var id: String?

    required init() {}
}

let jsonArrayString: String? = "[{\"name\":\"Bob\",\"id\":\"1\"}, {\"name\":\"Lily\",\"id\":\"2\"}, {\"name\":\"Lucy\",\"id\":\"3\"}]"
if let cats = [Cat].deserialize(from: jsonArrayString) {
    cats.forEach({ (cat) in
        // ...
    })
}

Mapping From Dictionary

HandyJSON support mapping swift dictionary to model.

var dict = [String: Any]()
dict["doubleOptional"] = 1.1
dict["stringImplicitlyUnwrapped"] = "hello"
dict["int"] = 1
if let object = BasicTypes.deserialize(from: dict) {
    // ...
}

Custom Mapping

HandyJSON let you customize the key mapping to JSON fields, or parsing method of any property. All you need to do is implementing an optional mapping function, do things in it.

We bring the transformer from ObjectMapper. If you are familiar with it, it’s almost the same here.

class Cat: HandyJSON {
    var id: Int64!
    var name: String!
    var parent: (String, String)?
    var friendName: String?

    required init() {}

    func mapping(mapper: HelpingMapper) {
        // specify 'cat_id' field in json map to 'id' property in object
        mapper <<<
            self.id <-- "cat_id"

        // specify 'parent' field in json parse as following to 'parent' property in object
        mapper <<<
            self.parent <-- TransformOf<(String, String), String>(fromJSON: { (rawString) -> (String, String)? in
                if let parentNames = rawString?.characters.split(separator: "/").map(String.init) {
                    return (parentNames[0], parentNames[1])
                }
                return nil
            }, toJSON: { (tuple) -> String? in
                if let _tuple = tuple {
                    return "\(_tuple.0)/\(_tuple.1)"
                }
                return nil
            })

        // specify 'friend.name' path field in json map to 'friendName' property
        mapper <<<
            self.friendName <-- "friend.name"
    }
}

let jsonString = "{\"cat_id\":12345,\"name\":\"Kitty\",\"parent\":\"Tom/Lily\",\"friend\":{\"id\":54321,\"name\":\"Lily\"}}"

if let cat = Cat.deserialize(from: jsonString) {
    print(cat.id)
    print(cat.parent)
    print(cat.friendName)
}

Date/Data/URL/Decimal/Color

HandyJSON prepare some useful transformer for some none-basic type.

class ExtendType: HandyJSON {
    var date: Date?
    var decimal: NSDecimalNumber?
    var url: URL?
    var data: Data?
    var color: UIColor?

    func mapping(mapper: HelpingMapper) {
        mapper <<<
            date <-- CustomDateFormatTransform(formatString: "yyyy-MM-dd")

        mapper <<<
            decimal <-- NSDecimalNumberTransform()

        mapper <<<
            url <-- URLTransform(shouldEncodeURLString: false)

        mapper <<<
            data <-- DataTransform()

        mapper <<<
            color <-- HexColorTransform()
    }

    public required init() {}
}

let object = ExtendType()
object.date = Date()
object.decimal = NSDecimalNumber(string: "1.23423414371298437124391243")
object.url = URL(string: "https://www.aliyun.com")
object.data = Data(base64Encoded: "aGVsbG8sIHdvcmxkIQ==")
object.color = UIColor.blue

print(object.toJSONString()!)
// it prints:
// {"date":"2017-09-11","decimal":"1.23423414371298437124391243","url":"https:\/\/www.aliyun.com","data":"aGVsbG8sIHdvcmxkIQ==","color":"0000FF"}

let mappedObject = ExtendType.deserialize(from: object.toJSONString()!)!
print(mappedObject.date)
...

Exclude Property

If any non-basic property of a class/struct could not conform to HandyJSON/HandyJSONEnum or you just do not want to do the deserialization with it, you should exclude it in the mapping function.

class NotHandyJSONType {
    var dummy: String?
}

class Cat: HandyJSON {
    var id: Int64!
    var name: String!
    var notHandyJSONTypeProperty: NotHandyJSONType?
    var basicTypeButNotWantedProperty: String?

    required init() {}

    func mapping(mapper: HelpingMapper) {
        mapper >>> self.notHandyJSONTypeProperty
        mapper >>> self.basicTypeButNotWantedProperty
    }
}

let jsonString = "{\"name\":\"cat\",\"id\":\"12345\"}"

if let cat = Cat.deserialize(from: jsonString) {
    print(cat)
}

Update Existing Model

HandyJSON support updating an existing model with given json string or dictionary.

class BasicTypes: HandyJSON {
    var int: Int = 2
    var doubleOptional: Double?
    var stringImplicitlyUnwrapped: String!

    required init() {}
}

var object = BasicTypes()
object.int = 1
object.doubleOptional = 1.1

let jsonString = "{\"doubleOptional\":2.2}"
JSONDeserializer.update(object: &object, from: jsonString)
print(object.int)
print(object.doubleOptional)

Supported Property Type

  • Int/Bool/Double/Float/String/NSNumber/NSString

  • RawRepresentable enum

  • NSArray/NSDictionary

  • Int8/Int16/Int32/Int64/UInt8/UInt16/UInt23/UInt64

  • Optional<T>/ImplicitUnwrappedOptional<T> // T is one of the above types

  • Array<T> // T is one of the above types

  • Dictionary<String, T> // T is one of the above types

  • Nested of aboves

Serialization

The Basics

Now, a class/model which need to serialize to JSON should also conform to HandyJSON protocol.

class BasicTypes: HandyJSON {
    var int: Int = 2
    var doubleOptional: Double?
    var stringImplicitlyUnwrapped: String!

    required init() {}
}

let object = BasicTypes()
object.int = 1
object.doubleOptional = 1.1
object.stringImplicitlyUnwrapped = “hello"

print(object.toJSON()!) // serialize to dictionary
print(object.toJSONString()!) // serialize to JSON string
print(object.toJSONString(prettyPrint: true)!) // serialize to pretty JSON string

Mapping And Excluding

It’s all like what we do on deserialization. A property which is excluded, it will not take part in neither deserialization nor serialization. And the mapper items define both the deserializing rules and serializing rules. Refer to the usage above.

FAQ

Q: Why the mapping function is not working in the inheritance object?

A: For some reason, you should define an empty mapping function in the super class(the root class if more than one layer), and override it in the subclass.

It's the same with didFinishMapping function.

Q: Why my didSet/willSet is not working?

A: Since HandyJSON assign properties by writing value to memory directly, it doesn't trigger any observing function. You need to call the didSet/willSet logic explicitly after/before the deserialization.

But since version 1.8.0, HandyJSON handle dynamic properties by the KVC mechanism which will trigger the KVO. That means, if you do really need the didSet/willSet, you can define your model like follow:

class BasicTypes: NSObject, HandyJSON {
    dynamic var int: Int = 0 {
        didSet {
            print("oldValue: ", oldValue)
        }
        willSet {
            print("newValue: ", newValue)
        }
    }

    public override required init() {}
}

In this situation, NSObject and dynamic are both needed.

And in versions since 1.8.0, HandyJSON offer a didFinishMapping function to allow you to fill some observing logic.

class BasicTypes: HandyJSON {
    var int: Int?

    required init() {}

    func didFinishMapping() {
        print("you can fill some observing logic here")
    }
}

It may help.

Q: How to support Enum property?

It your enum conform to RawRepresentable protocol, please look into Support Enum Property. Or use the EnumTransform:

enum EnumType: String {
    case type1, type2
}

class BasicTypes: HandyJSON {
    var type: EnumType?

    func mapping(mapper: HelpingMapper) {
        mapper <<<
            type <-- EnumTransform()
    }

    required init() {}
}

let object = BasicTypes()
object.type = EnumType.type2
print(object.toJSONString()!)
let mappedObject = BasicTypes.deserialize(from: object.toJSONString()!)!
print(mappedObject.type)

Otherwise, you should implement your custom mapping function.

enum EnumType {
    case type1, type2
}

class BasicTypes: HandyJSON {
    var type: EnumType?

    func mapping(mapper: HelpingMapper) {
        mapper <<<
            type <-- TransformOf<EnumType, String>(fromJSON: { (rawString) -> EnumType? in
                if let _str = rawString {
                    switch (_str) {
                    case "type1":
                        return EnumType.type1
                    case "type2":
                        return EnumType.type2
                    default:
                        return nil
                    }
                }
                return nil
            }, toJSON: { (enumType) -> String? in
                if let _type = enumType {
                    switch (_type) {
                    case EnumType.type1:
                        return "type1"
                    case EnumType.type2:
                        return "type2"
                    }
                }
                return nil
            })
    }

    required init() {}
}

Credit

  • reflection: After the first version which used the swift mirror mechanism, HandyJSON had imported the reflection library and rewrote some code for class properties inspecting.
  • ObjectMapper: To make HandyJSON more compatible with the general style, the Mapper function support Transform which designed by ObjectMapper. And we import some testcases from ObjectMapper.

License

HandyJSON is released under the Apache License, Version 2.0. See LICENSE for details.

GitHub

https://github.com/alibaba/handyjson