Swift showing error when serializing data - ios

Question

When I try to serialize json data in swift I get this error
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid type in JSON write (__SwiftValue)'
Here is the code that is creating this issue:
request.httpBody = try? JSONSerialization.data(withJSONObject: data, options: [])
my data variable looks something like this:
let data = ["first_name": "John", "last_name": "Riverson", "post_info: userPost(title: "Some title", date_published: "some date")] as [String: Any]
I issue is caused due to the userPost struct, but I am not sure how to fix it.

Answer 1

It seems the result of userPost is not available for JSON.
According to JSONSerialization
A Foundation object that may be converted to JSON must have the following properties:
The top level object is an NSArray or NSDictionary.
All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
All dictionary keys are instances of NSString.
Numbers are not NaN or infinity
If you want to make userPost could be accpeted by JSONSerialization, refer to Using JSON with Custom Types, and apply Codable to it.

Answer 2

Your analysis is correct that it's due to the struct.
As per the documentation on JSONSerialization:
Foundation object that may be converted to JSON must have the
following properties:
The top level object is an NSArray or NSDictionary.
All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
All dictionary keys are instances of NSString.
Numbers are not NaN or infinity.
Ref:
https://developer.apple.com/documentation/foundation/jsonserialization
So you will need to convert the struct to dictionary to insert it here.
Something like:
let userPostDict: [String:Any] = //... your logic e.g. userPost.toDictionary
let data = ["first_name": "John",
"last_name" : "Riverson",
"post_info" : userPostDict]
You could have a toDictionary computed property inside your userPost struct that gives you a [String:Any]
Example:
extension YourStruct {
var toDictionary: [String:Any] {
//make the dictionary & return here
}
}