Update and append decoded JSON into struct? - swift

Question

I'm receiving some paginated JSON response through my API that looks something like this:
page 1:
{
"count": 96,
"next": "http://127.0.0.1:8000/id=5/?page=2",
"previous": null,
"results": [
{
"id": 10,
"book_name": "Book name",
"book_id": 70,
"chapter_number": 1,
"verse": "Verse title here",
"verse_number": 1,
"chapter": 96
},
{
"id": 198,
"book_name": "Book Name",
"book_id": 70,
"chapter_number": 8,
"verse": "Text here",
"verse_number": 5,
"chapter": 103
}
]
}
As I move through the paginated result, ie calling: http://127.0.0.1:8000/id=5/?page=2
I'll get new values in the results array.
page 2:
{
"count": 96,
"next": "http://127.0.0.1:8000/id=5/?page=3",
"previous": "http://127.0.0.1:8000/id=5/",
"results": [
{
"id": 206,
"book_name": "Book on Second page",
"book_id": 70,
"chapter_number": 8,
"verse": "yadda yadda",
"verse_number": 13,
"chapter": 103
},
{
"id": 382,
"book_name": "Book on second page..",
"book_id": 70,
"chapter_number": 15,
"verse": "Verse here",
"verse_number": 12,
"chapter": 110
}
]
}
How would I structure my struct/fix my decoding so I can append the values of results from the JSON while still updating count, next and previous as I go through ..?page=3, ..?page=4 etc
Currently, my struct looks like this:
struct VersesSearchResult: Decodable {
var results: [Verse]
var count: Int
var next: String?
var previous: String?
}
When doing the decoding, I'm not sure what the syntax should be like to append results to the struct, and update next, previous, and count. So far I got this
...
let verses = try JSONDecoder().decode(VersesSearchResult, from: safeData)
DispatchQueue.main.async {
// somehow need to get this to work - not entirely sure how
// where results gets appended, while the rest in the JSON values gets updated
// obviously I can't do as below:
self.verseSearchResult.append(contentsOf: verses.results)
self.verseSearchResult = verses
}
...

Answer 1

Decode to a temprary instance of the type, then process those properties into your main instance. Depending how you want to process the data, it'll look something like this
extension VersesSearchResult {
mutating func update(with new: VersesSearchResult) {
results.append(new)
count = new.count
next = new.next
prev = new.prev
}
}
and then in your completion block
let newVerses = try JSONDecoder().decode(VersesSearchResult, from: safeData)
self.verses.update(with: newVerses)
If needs be force the update onto the main thread.
You should also handle failure in the 'try' either with a do...catch or other approach.