ignore null object in array when parse with Codable swift - json

Question

i'm parsing this API with swift Codable
"total": 7,
"searchResult": [
null,
{
"name": "joe"
"family": "adam"
},
null,
{
"name": "martin"
"family": "lavrix"
},
{
"name": "sarah"
"family": "mia"
},
null,
{
"name": "ali"
"family": "abraham"
}
]
with this PaginationModel:
class PaginationModel<T: Codable>: Codable {
var total: Int?
var data: T?
enum CodingKeys: String, CodingKey {
case total
case data = "searchResult"
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.total = try container.decodeIfPresent(Int.self, forKey: .total)
self.data = try container.decodeIfPresent(T.self, forKey: .data)
}
}
and User Model:
struct User: Codable {
var name: String?
var family: String?
}
i call jsonDecoder like this to parse API json:
let responseObject = try JSONDecoder().decode(PaginationModel<[User?]>.self, from: json)
now my problem is null in searchResult Array. it parsed correctly and when i access to data in paginationModel i found null in array.
how can i ignore all null when parsing API, and result will be an array without any null

Answer 1

In the first place, I would advise to always consider PaginationModel to be composed from arrays. You don't have to pass [User] as the generic type, you can just pass User. Then the parser can use the knowledge that it parses arrays and handle null automatically:
class PaginationModel<T: Codable>: Codable {
var total: Int?
var data: [T]?
enum CodingKeys: String, CodingKey {
case total
case data = "searchResult"
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.total = try container.decodeIfPresent(Int.self, forKey: .total)
self.data = (try container.decodeIfPresent([T?].self, forKey: .data))?.compactMap { $0 }
}
}
You might want to remove optionals here and use some default values instead:
class PaginationModel<T: Codable>: Codable {
var total: Int = 0
var data: [T] = []
enum CodingKeys: String, CodingKey {
case total
case data = "searchResult"
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.total = (try container.decodeIfPresent(Int.self, forKey: .total)) ?? 0
self.data = ((try container.decodeIfPresent([T?].self, forKey: .data)) ?? []).compactMap { $0 }
}
}

Answer 2

Simple solution, filter data after decoding
let responseObject = try JSONDecoder().decode(PaginationModel<[User?]>.self, from: data)
responseObject.data = responseObject.data?.filter{$0 != nil}

Answer 3

You may add an array type check within decode :
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.total = try container.decodeIfPresent(Int.self, forKey: .total)
self.data = try container.decodeIfPresent(T.self, forKey: .data)
//add the following:
if let array = self.data as? Array<Any?> {
self.data = ( array.compactMap{$0} as? T)
}
}

Answer 4

Note, you can just define the decodable variable that may be null/nil as [Float?] (or whatever type), with the optional '?' inside the array brackets.