Swift: write JSON and save to iPhone File locally - ios

Question

I am learning how to write JSON format data to an iPhone. So with one button clicked, I want to save those data to the iPhone. I looked a simple look on how to write some simple text and saved it to the iPhone file and it worked. However, I tried to apply the same idea to JSON data but still haven't figure out. I tried:
Rather than having contents equal to some written text, I tried to put it as my data (jsondata).
But it does not seem working with
try jsondata.write(to: fileURL, atomically: false, encoding: .utf8)
#IBAction func writeFiles(_ sender: Any) {
let file = "\(UUID().uuidString).txt"
let contents = "Testing"
let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let fileURL = dir.appendingPathComponent(file)
do {
try contents.write(to: fileURL, atomically: false, encoding: .utf8)
}
catch {
print("Error: \(error)")
}
}
Sorry I am a bit new and learning Swift at the moment
Thanks!

Answer 1

Here is a simple project for you to clone or browse the source files
https://github.com/eSpecialized/WriteJsonToFiles
The View Controller contains the example;
https://github.com/eSpecialized/WriteJsonToFiles/blob/master/WriteToFiles/ViewController.swift
Basically you need to do a few steps for writing;
Assemble your objects (Strings etc).
Convert to JSONEncoded Data using the JSONEncoder.
The actual 'Data' Object can write it's binary content to storage.
To read the data;
You need a JSONDecoder.
You need the FileContents in memory using Data(contents:...)
Decode the in-memory data back into the object like it was stored.
A more complicated example of reading and writing JSON to a Web Service API is on Medium here > https://medium.com/better-programming/json-parsing-in-swift-2498099b78f
The concepts are the same, the destination changes from a file in the users document folder to a web service API. I feel that it is adequate to get you started with reading and writing JSON.
The Medium article goes a step further with introducing you to Data Models and reading and writing those Data Model Structs using the Codable protocol.
Enjoy! :)