Reading JSON into array then writing it back to JSON Swift? - ios

Question

New to IOS development and JSON stuff. I have a struct for Recipe which includes things like name, ingredients, instructions, etc. I have an array of Recipes. When my app is first run, I read data from a JSON file into the array of recipes so the app isn't empty at first. Throughout the app I append to the array of recipes. How would I go about writing the array back to the file everytime the array is changed? Here is some of the code and things I have tried.
Recipe Struct:
struct Recipe : Codable, Identifiable {
var id: String
var name: String
var ingredients: [String]
var instructions: [String]
var category: String
var imageName: String
}
Reading from JSON into recipe array:
import UIKit
import SwiftUI
var recipeData: [Recipe] = loadJson("recipeData.json")
func loadJson<T: Decodable>(_ filename: String) -> T {
let data: Data
guard let file = Bundle.main.url(forResource: filename,withExtension: nil)
else {
fatalError("\(filename) not found.")
}
do {
data = try Data(contentsOf: file)
} catch {
fatalError("Could not load \(filename): \(error)")
}
do {
return try JSONDecoder().decode(T.self, from: data)
} catch {
fatalError("Unable to parse \(filename): \(error)")
}
}
My attempt to write back to a json file once array is changed(appended to):
func writeJson(){
var jsonArray = [String]()
if let documentDirectory = FileManager.default.urls(for: .documentDirectory,
in: .userDomainMask).first {
let pathWithFilename = documentDirectory.appendingPathComponent("test.json")
for recipe in recipeData{
do{
let encodedData = try JSONEncoder().encode(recipe)
let jsonString = String(data: encodedData, encoding: .utf8)
print(jsonString!)
jsonArray.append(jsonString!)
try jsonString!.write(to: pathWithFilename,
atomically: true,
encoding: .utf8)
}catch{
print(error)
}
}
}
}
This all builds successfully but nothing is written to my tests.json file. I am very new so any help would be appreciated. Thank you.

Answer 1

try jsonString!.write(to: pathWithFilename,
atomically: true,
encoding: .utf8)
This method erases the existing file and replaces it with the data in question. You do this in a loop, so you're going to overwrite the file many times, always with a single recipe. My expectation is that this would always leave just the last recipe in the file.
I believe what you meant to do is:
// Encode all the recipes, not one at a time.
let encodedData = try JSONEncoder().encode(recipeData)
// Write them. There's no reason to convert to a string
encodedData.write(to: pathWithFilename, options: [.atomic])
As a beginner, this is probably fine. A more professional approach would likely spread this data over multiple files, use a database, or Core Data. But for small projects with only a few data items, writing a single JSON file is fine.