Issue decoding JSON | Swift

Question

I am having an issue dynamically populating the date associated with each section. The value of grouped is currently derived from grouping the raw JSON data by routeid

You can see that I am currently using a static value for date as a test, while $0.key represent the value of myID dynamically.

How can also add the dynamic value of myDate intead of "test"?

Variables:

var sections = [mySections]()
var structure = [myStructure]()

Currently this is true

sections.map(\.id) == [8,4]

At the end this must be true as well

sections.map(\.date) == [2021-01-20, 2021-01-18]

Decoding:

do {
      let decoder = JSONDecoder()
      let res = try decoder.decode([myStructure].self, from: data)
      let grouped = Dictionary(grouping: res, by: { $0.myID })
      _ = grouped.keys.sorted()
      sections = grouped.map { mySections(date: "test", id: $0.key, items: $0.value) }
      .sorted { $0.id > $1.id }
}

Struct:

struct mySections {
    let date : String
    let id : Int
    var items : [myStructure]
}

struct myStructure: Decodable {
    let name: String
    let type: String
    let myID: Int
    let myDate: String
}

Example JSON:

[
  {
    "name": "Jeff",
    "type": "large",
    "myID": 8,
    "myDate": "2021-01-20"
  },
  {
    "name": "Jessica",
    "type": "small",
    "myID": 4,
    "myDate": "2021-01-18"
  },
  {
    "name": "Beth",
    "type": "medium",
    "myID": 4,
    "myDate": "2021-01-18"
  }
]

I am trying to produce the output and run your current code. What is routeStructure meant to be ? Is it a type of mySections ? — Shawn Frank
– Shawn Frank, Commented Jan 21, 2022 at 1:53
Please see Rob's answer below, I tested it and works a treat with your data. — Shawn Frank
– Shawn Frank, Commented Jan 21, 2022 at 2:35

Rob · Accepted Answer · 2022-01-21 01:54:45Z

1

So, you want it grouped by both id number and date string? I would create a Hashable structure for those two values.

struct Section {
    let date: String
    let id: Int
    var items: [Item]
}

extension Section {
    struct Header: Hashable {
        let date: String
        let id: Int
    }
}

struct Item: Decodable {
    let name: String
    let type: String
    let myID: Int
    let myDate: String
}

And

let decoder = JSONDecoder()
let res = try decoder.decode([Item].self, from: data)
let sections = Dictionary(grouping: res) { Section.Header(date: $0.myDate, id: $0.myID) }
    .sorted { $0.key.id > $1.key.id }
    .map { Section(date: $0.key.date, id: $0.key.id, items: $0.value) }

answered Jan 21, 2022 at 1:54

Rob

441k74 gold badges850 silver badges1.1k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Rob Over a year ago

Forgive the renaming of the types. Re myStructure to Item, I wanted to (a) follow capitalization conventions (we never have type names that start with a lowercase letter); and (b) Structure is just too ambiguous. While I was renaming stuff, I’m not sure why you’d call it mySections when (a) each one represents a single section; and (b) same capitalization concerns.

Collectives™ on Stack Overflow

Issue decoding JSON | Swift

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related