saoudrizwan/dynamicjson

Access JSON properties dynamically like JavaScript using Swift 4.2's new @dynamicMemberLookup feature

Installation • Usage • License

DynamicJSON is a dynamically typed JSON parser built upon the new @dynamicMemberLookup feature introduced by Chris Lattner in Swift 4.2. This allows us to access arbitrary object members which are resolved at runtime, allowing Swift to be as flexible as JavaScript when it comes to JSON.

Before

if let jsonObject = try? JSONSerialization.jsonObject(with: data, options: []) as? [String: Any],
   let user = jsonObject["user"] as? [String: Any],
   let username = user["username"] as? String {
	// ...
}

After

let username = JSON(data).user.username.string

Installation

• CocoaPods:

pod 'DynamicJSON', '~> 2.0.2'

(if you run into problems, pod repo update and try again)

• Carthage:

github "saoudrizwan/DynamicJSON"

• Or drag and drop DynamicJSON.swift into your project.

And import DynamicJSON in the files you'd like to use it.

Usage

1. Initialize 🐣

Throw Anything into a JSON object to get started

let json = JSON(Data())
           JSON(123)
           JSON(["key": "value"])
           JSON(["element", 1])
           JSON("Hello world")
           JSON(false)

...or cast a literal as JSON

let json = "Hello world" as JSON
           123 as JSON
           [1, 2, 3] as JSON

let user: JSON = [
	"username": "Saoud",
	"age": 21,
	"address": [
	    "zip": "12345",
	    "city": "San Diego"
	]
]

2. Drill in ⛏

Treat JSON objects like you're in JavaScript Land

let dictionary = json.dictionary
let array = json[0].cars.array
let string = json.users[1].username.string
let nsnumber = json.creditCard.pin.number
let double = json[3][1].height.double
let int = json[0].age.int
let bool = json.biography.isHuman.bool

Note how JSON doesn't actually have properties like cars or users, instead it uses dynamic member lookup to traverse through its associated JSON data to find the object you're looking for.

In case you have a key that's an actual property of JSON, like number or description for example, just use the string subscript accessor like so:

let number = json.account.contact["number"].number
let description = json.user.biography["description"].string

3. Have fun 🤪

JSON conforms to Comparable

let json1 = JSON(jsonData1)
let json2 = JSON(jsonData2)

// Equality applies to all types (Dictionary, Array, String, NSNumber, Bool, NSNull)
let isEqual = json1 == json2

// Less/greater than only applies to NSNumbers (Double, Int) and Strings
let isLessThan = json1 < json2
let isLessThanOrEqual = json1 <= json2
let isGreaterThan = json1 > json2
let isGreaterThanOrEqual = json1 >= json2

Pretty print for debug purposes

print(json)

Convert to raw object

let anyObject = json.object

Convert to Data

let data = json.data() // optionally specify options...

License

DynamicJSON uses the MIT license. Please file an issue if you have any questions or if you'd like to share how you're using DynamicJSON.

Contribute

DynamicJSON is in its infancy, but provides the barebones of a revolutionary new way to work with JSON in Swift. Please feel free to send pull requests of any features you think would add to DynamicJSON and its philosophy.

Questions?

Contact me by email [email protected], or by twitter @sdrzn. Please create an issue if you come across a bug or would like a feature to be added.

Notable Mentions

• Paul Hudson's wonderful literature over @dynamicMemberLookup
• Chris Lattner's Swift Evolution Propsal SE-0195
• SwiftyJSON for giving me a better idea of what the community wants out of a JSON parser
• Helge Heß for helping remove the need to use optional chaining (before v2.0.0)

dynamicjson's Issues

JSON values aren't decomposed in JSON dictionary literals

Composing a dictionary literal with JSON properties results in those properties being null, instead of decomposing them into dictionaries themselves. For example, when

let foo = ["foo": 3] as JSON
let bar = ["bar": foo] as JSON

bar should equal

[
    "foo": [
        "bar": 3
    ]
] as JSON

However, bar actually equals

[
    "foo": JSON.null
] as JSON

To fix this issue, the JSON.init(_ object: Any) initializer should set self to object when object is an instance of JSON. I'll submit a PR for this later today; let me know what you think!

Codable support

I hope add a method Codable to JSON, could you help me

Treat optionals as `JSON.null` to remove all the explicit unwrapping

The thing you present primarily looks ugly because of the optional chaining at every single step:

if let street = json.person?.address?[0].street.stringValue { }

But it doesn't have to be like that (it is dynamic anyways). I think you could improve that a lot by essentially adding "nil messaging":

if let street = json.person.address[0].street.stringValue { .. }

Instead of returning an optional in every item of the chain, only make the leaf accessors (stringValue, intValue, etc) optional. When a lookup is not successful, return JSON.null (which itself returns JSON.null on all JSON accesses, so that the result propagates).

If you'd like you could also add a JSON.lookupError(parent, key) as a result for missed lookups for debugging purposes (and which also propagates down the call chain, and could even persist the lookup path from the root of the first lookup failure).

How can I convert Dictionary<String,Any> to JSON?

I used the source code in a playground, and when I want to create a JSON object from a dictionary (it is [String: Any]), it gives me this:

error: Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0).

I used this:

let dictionary: [String: Any] = [
  "name"    : "Omid",
  "age"     : 29,
  "married" : false
]

let dictionaryAsJSON = JSON(dictionary)

print(dictionaryAsJSON.description)

I think it is only in runtime, because Xcode does not show any issue, until running plaground.

README Assets (ignore)