Decoding JSON when feed is inconsistent - Swift - ios

Question

I don’t know how to handle a JSON feed in swift with the decodable protocol when the feed gives me two different results. If there is more than one ‘entry’, the json looks like this and the entry value is an array of objects
{
"feed": {
"publisher": "Penguin",
"country": "ca"
},
"entry": [
{
"author": "Margaret Atwood",
"nationality": "Canadian"
},
{
"author": "Dan Brown",
"nationality": "American"
}
]
}
However, if there is only a single entry, the json looks like this where entry is just a dictionary
{
"feed": {
"publisher": "Penguin",
"country": "ca"
},
"entry": {
"author": "Margaret Atwood",
"nationality": "Canadian"
}
}
to decode the first case, I would use the following structs
struct Book: Decodable {
let feed: Feed
let entry: [Entry]
}
// MARK: - Entry
struct Entry: Decodable {
let author, nationality: String
}
// MARK: - Feed
struct Feed: Decodable {
let publisher, country: String
}
And then use something like this to decode the data retrieved
let object = try JSONDecoder().decode(Book.self, from: data)
How do I handle the case when the entry is not an array of objects?

Answer 1

You could possibly override the decoder for Book. What you can do is to try to unwrap an [Entry]s and upon failing that, just try to unwrap a single Entry.
For example:
struct Book: Decodable {
let feed: Feed
let entry: [Entry]
init (from decoder :Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
do {
value = try container.decode([Entry].self, forKey: .value)
} catch {
let newValue = try container.decode(Entry.self, forKey: .value)
value = [newValue]
}
}
}
Note: that's not a comprehensive sample on what you want to do but just a way you can accomplish what you want to do