How to include null value in the JSON via NSJSONSerialization?

You have to use NSNull. For instance

Swift

let dict = ["firstKeyHasValue": 2342, "secondKeyHasNoValue": NSNull()]

Objective-C

NSDictionary *dict = @{ @"error": [NSNull null] };

From the official documentation of NSDictionary:

Neither a key nor a value can be nil; if you need to represent a null value in a dictionary, you should use NSNull.

I tried doing this and worked for me.

var param: [String:Any] = [:]param["firstName"] = "somename"param["middleName"] = NSNull()param["lastName"] = "somename"print(param)

Result:

["firstName":"somename","middleName":null,"lastName":"somename"]

If you are using Swifty JSON, I've just created a PR that should handle nil. It's not merged yet and might need some improvements.The part that describes how to do that should be a good start to write your own implementation if you need to. The logic is not that complicated but there might be tricky edge cases/performance things to think about.

I know it's not a direct response to the question since it's replacing NSJSONSerialization, but I hope it can help some people frustrated by how Swift handles nil/json!