Initialisation using nil or NSNull

[cjmconie]

Currently, initialisation from an Any type does not allow nil or NSNull values (as far as I can tell). Would it make sense to support this?

There are two use cases I have run across:

1. Initialising using a Swift dictionary containing nil:

let modelUsingNil: Any = [
            "foo": "hello",
            "bar": nil
        ]
        
let json1 = try! JSON(modelUsingNil) // Thread 1: Fatal error: 'try!' expression unexpectedly raised an error
print(json1)

2. Initialising using an object containing NSNull. For example deserialising a json object JSONSerialization.jsonObject().

let jsonData = try! JSONSerialization.data(withJSONObject: modelUsingNil)
let modelWithNSNull = try! JSONSerialization.jsonObject(with: jsonData)
print(modelWithNSNull)

// see: https://stackoverflow.com/a/28024012/3589408
let json2 = try! JSON(modelWithNSNull) // Thread 1: Fatal error: 'try!' expression unexpectedly raised an error
print(json2)

Potential solution (wip)

For NSNull initialisation, the following could work:

extension JSON {
    public init(_ value: Any) throws {
        switch value {
        case _ as NSNull: 
            self = .null
        case let num as Float:
            self = .number(num)
        case let num as Int:
            self = .number(Float(num))
        case let str as String:
            self = .string(str)
        case let bool as Bool:
            self = .bool(bool)
        case let array as [Any]:
            self = .array(try array.map(JSON.init))
        case let dict as [String: Any]:
            self = .object(try dict.mapValues(JSON.init))
        default:
            throw BVJSONError.decodingError
        }
    }
}

[zoul]

Makes sense! Short test case:

XCTAssertEqual(try JSON(Optional<Int>.none as Any), .null)
XCTAssertEqual(try JSON(NSNull()), .null)

The proposed NSNull initialization works well, I’ll think about the nil case in a moment.

[zoul]

This works for me:

--- a/GenericJSON/Initialization.swift
+++ b/GenericJSON/Initialization.swift
@@ -9,6 +9,10 @@ extension JSON {
     /// of those types.
     public init(_ value: Any) throws {
         switch value {
+        case _ as NSNull:
+            self = .null
+        case let opt as Optional<Any> where opt == nil:
+            self = .null
         case let num as Float:
             self = .number(num)
         case let num as Int:

I have to run now, will write some tests to check for corner cases later, the relationship between Any and Optional is a bit iffy.

[zoul]

I’ve pushed my working version, can you please try that?

[cjmconie]

I have added a further comment to the commit regarding the unit tests, but it is more a question of interest. I would consider this issue resolved. 😄

[zoul]

🎉