How to declare a multidimensional String in Realm? - swift

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Dipesh Pokhrel wants to draw more attention to this question:
I have gone throught the documentation no where its specifically mentioned. how to deal with the multidimensional string objects
I have a realm class which contains the a multi dimensional string, realm in Decodable is throwing an error to while parsing, created class to support realm.
class Categories : Object,Decodable {
// var assetSum : [[String]]? // In swift originally
let assetSum = RealmSwift.List<String>() // modified to support list
#objc var id : String?
#objc var dn : String?
How to fix this , to be more Generalise how to store var assetSum : [[String]]? this kind of value in realm?
I have gone through the documentation of realm but could not find something related to this

Answer 1

Realm supports basic types like Int, String, Date etc. and several collections types like List (Array), Map (Dictionary) from the box. For the other your custom types you can use json serialization which works pretty quick.
It can be implemented with two variables where persistent private one is for storing data and public one is for accessing e.g:
import RealmSwift
class Categories: Object {
#Persisted private var assetSum: Data?
var assetSumValue: [[String]]? {
get {
guard let value = assetSum else {
return nil
}
return try? JSONDecoder().decode(([[String]]?).self, from: value)
}
set {
assetSum = try? JSONEncoder().encode(newValue)
}
}
}
Now you can easy set/get values with assetSumValue:
// Create and save
let categories = Categories()
try realm.write {
categories.assetSumValue = [["1", "2", "3"], ["4", "5", "6"]]
realm.add(categories)
}
// Get first element from DB
if let categories = realm.objects(Categories.self).first,
let value = categories.assetSumValue
{
print(value) // Prints: [["1", "2", "3"], ["4", "5", "6"]]
}
In case of encoding/decoding your custom Realm types with complex properties you should implement a custom decoder:
class Categories: Object, Codable {
#Persisted var id: String?
#Persisted var dn: String?
#Persisted private var assetSum: Data?
var assetSumValue: [[String]]? {
get {
guard let value = assetSum else {
return nil
}
return try? JSONDecoder().decode(([[String]]?).self, from: value)
}
set {
assetSum = try? JSONEncoder().encode(newValue)
}
}
override init() {
super.init()
}
required init(from decoder: Decoder) throws {
super.init()
let values = try decoder.container(keyedBy: CodingKeys.self)
id = try values.decode((String?).self, forKey: .id)
dn = try values.decode((String?).self, forKey: .dn)
assetSumValue = try values.decode(([[String]]?).self, forKey: .assetSum)
}
}
How to decode:
let json = """
{
"id": "100",
"dn": "200",
"assetSum": [
["one", "two", "three"],
["four", "five", "six"]
]
}
"""
let categories = try JSONDecoder().decode(Categories.self, from: json.data(using: .utf8)!)
if let value = categories.assetSumValue {
print(value) // Prints [["one", "two", "three"], ["four", "five", "six"]]
}