Swift Codable, array value as key - json

Question

So this is my JSON:
{
"items": [{
"name": "Item 1",
"description": "This is Item 1",
"categories": ["Category1", "Category2", "Category3", "Category4"],
"size": ["M", "L"]
},{
"name": "Item 2",
"description": "This is Item 2",
"categories": ["Category1", "Category3", "Category4"],
"size": ["M"]
}]
}
I can read and print it perfectly fine
However, I want to change this structure to this one where each item is separated by category and size, and where the categories are used as keys.
{
"categories": {
"category1": [{
"name": "Item 1",
"description": "This is Item 1",
"size": "M"
},{
"name": "Item 1",
"description": "This is Item 1",
"size": "L"
},{
"name": "Item 2",
"description": "This is Item 2",
"size": "M"
}...],
"category2": [{
...
}]
}
I've created the following data structure but I'm not quite sure how to continue:
struct Categories: Codable {
let category: String
let items: [Item]
struct Item: Codable {
let name, description, size: String
}
}
Is Codable the right solution for this? If so; how would I go on to achieve this?

Answer 1

For your current json you need
struct Root: Codable {
let categories: [String:[Item]]
}
struct Item: Codable {
let name, description, size: String
}
But I think it's better to make it like this
{
"category1": [{
"name": "Item 1",
"description": "This is Item 1",
"size": "M"
},{
"name": "Item 1",
"description": "This is Item 1",
"size": "L"
},{
"name": "Item 2",
"description": "This is Item 2",
"size": "M"
}],
"category2": [{
}]
}
Which will make you do this
let res = try? JSONDecoder().decode([String:[Item]].self,from:jsonData)
Without the Root struct and the useless categories key