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Khoa Pham
Khoa Pham

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Primary key in Realm

Original post

Realm is great. But without primary key, it will duplicate the record, like,, ... So to force ourselves into the good habit of declaring primary key, we can leverage Swift protocol

Create primary constrain protocol like this

protocol PrimaryKeyAware {
  var id: Int { get }
  static func primaryKey() -> String?
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and conform it in out Realm object

class Profile: Object, PrimaryKeyAware {

  dynamic var firstName: String = ""
  dynamic var lastName: String = ""
  dynamic var id: Int = 0

  override static func primaryKey() -> String? {
    return "id"
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This way, when using that object in out RealmStorage, we are safe to say that it has a primary key

class RealmStorage<T: Object> where T: PrimaryKeyAware {
  let realm: Realm

  init(realm: Realm = RealmProvider.realm()) {
    self.realm = realm

  func save(_ objects: [T]) {
    try? realm.write {
      realm.add(objects, update: true)
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The usage is like this

let profile = Profile()
let storage = RealmStorage<Profile>()[profile])
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