Combine JSON and String in a dictionary with Swifty - json

Question

I'd like to create a JSON object in Swifty that has the form:
{
"store": {
"id": {
"test": "test"
},
"type": "retail",
"name": "store1"
}
}
Is there a way to combine types in a Dictionary to use with Swifty (String and JSON)? Quotes works, but when I try to assign a variable, it complains: Cannot assign value of type 'String' to type 'JSON?':
func jsonTest()->String {
var storeJson = [String: JSON]()
var someJson = JSON(["test":"test"])
storeJson["id"] = someJson
storeJson["type"] = "retail" // <-- works fine
var name = "store1"
storeJson["name"] = name // <-- Doesn't work
var store = JSON(storeJson)
return store.rawString()!
}

Answer 1

The reason
storeJson["type"] = "retail"
works differently than
storeJson["name"] = name
is because the first one follows a different path in the code. Specifically, it uses the init(stringLiteral value: StringLiteralType) method in the following extension (source).
extension JSON: Swift.StringLiteralConvertible {
public init(stringLiteral value: StringLiteralType) {
self.init(value)
}
public init(extendedGraphemeClusterLiteral value: StringLiteralType) {
self.init(value)
}
public init(unicodeScalarLiteral value: StringLiteralType) {
self.init(value)
}
}
I'll explain further after we talk about how to fix your specific problem.
Possible solution #1:
storeJson["name"]?.string = name
Output:
{
"id" : {
"test" : "test"
},
"type" : "retail"
}
The reason
storeJson["name"]?.string = name
doesn't work as we might think is because of the optional chaining. Right now, if we ran this through the debugger, we wouldn't see anything meaningful. In fact, we would see nothing. This is a bit concerning and likely means storeJson["name"] is nil, so the statement is not executing any further. Let's verify our hypothesis by making it blow up. We'll change the line to:
storeJson["name"]!.string = name
In this case, with your current code, you'll likely get
fatal error: unexpectedly found nil while unwrapping an Optional value
as you should because storeJson["name"] is in fact nil. Therefore, this solution doesn't work.
Possible solution #2:
As you correctly noted in your answer, if you add a storeJson["name"] = JSON(name), you'll get the desired behavior:
func jsonTest()->String {
var storeJson = [String: JSON]()
var someJson = JSON(["test":"test"])
storeJson["id"] = someJson
storeJson["type"] = "retail" // <-- works fine
var name = "store1"
storeJson["name"] = JSON(name) // <-- works!
var store = JSON(storeJson)
return store.rawString()!
}
Output:
{
"id" : {
"test" : "test"
},
"name" : "store1",
"type" : "retail"
}
Great! Therefore, this solution works! Now, later in your code you can alter it however you want using .string and the like.
Explanation
Back to why the string literal works. You'll notice in the init, it has
self.init(value)
which passes through the objects init, which then goes through the case statement
...
case let string as String:
_type = .String
self.rawString = string
...
When you call storeJson["name"] = JSON(name), you're skipping the StringLiteralType init and simply going into the switch.
Therefore, you could interchange
storeJson["type"] = "retail"
with
storeJson["type"] = JSON("retail")

Answer 2

It turns out it works to change:
storeJson["name"] = name
to
storeJson["name"] = JSON(name)