Disk-delete-by-id.swift

struct Message {
  let id: String
  let body: String
}

let messages = [Message(id: "1", body: "..."), Message(id: "2", body: "..."), Message(id: "3", body: "...")]
// or retrieve your messages from Disk...
let messages = try! Disk.retrieve("messages.json", from: .documents, as: [Message].self)

var messagesWithoutIdOf2 = [Message]()
for message in messages where message.id != 2 {
  messagesWithoutIdOf2.append(message)
}
// or if you want to get functional...
let messagesWithoutIdOf2 = messages.filter { $0.id != 2 }

// now save this updated array to disk...
try! Disk.save(messagesWithoutIdOf2, to: .documents, as: "messages.json")