Add arrays to Realm with swift 3 - ios

Question

I'm new in Realm and I tried to add an Array as I did with strings and I ended up with some errors. So after a little search I found out a solution:
class Sensors : Object {
dynamic var name = ""
dynamic var message = ""
var topic: [String] {
get {
return _backingNickNames.map { $0.stringValue }
}
set {
_backingNickNames.removeAll()
_backingNickNames.append(objectsIn: newValue.map({ RealmString(value: [$0]) }))
}
}
let _backingNickNames = List<RealmString>()
override static func ignoredProperties() -> [String] {
return ["topic"]
}
}
class RealmString: Object {
dynamic var stringValue = ""
}
This is working very good, now I want to add another array inside this class.
If someone knows any other ways to add arrays with realm please share it.
Thanks in advance

Answer 1

As a general rule it's way more efficient to use the one-to-many relationships provided by Realm instead of trying to emulate them by using arrays (Realm's collections are lazy, the objects contained are instantiated only when needed as opposed to plain Swift arrays).
In your case, if I understand correctly what you're trying to do, you want to add [RealmString] Swift arrays to the _backingNickNames list.
Why not use the append(objectsIn:) method of Realm's List class (see here), like this:
// Dog model
class Dog: Object {
dynamic var name = ""
dynamic var owner: Person?
}
// Person model
class Person: Object {
dynamic var name = ""
dynamic var birthdate = NSDate(timeIntervalSince1970: 1)
let dogs = List<Dog>()
}
let jim = Person()
let dog1 = Dog()
let dog2 = Dog()
// here is where the magic happens
jim.dogs.append(objectsIn: [dog1, dog2])
If you want to do the opposite (convert from a List to an Array) just do :
let dogsArray = Array(jim.dogs)
• • • • • • • •
Back to your own posted solution, you could easily refactor the model to accommodate this. Each Sensor object could have several Topic and several Message objects attached.
Just ditch the message and topic computed properties and rename topicV and messageV to topics and messages respectively. Also rename RealmString to Topic and RealmString1 to Message.
Now, you could easily iterate through the, say, topics attached to a sensor like this :
for topic in sensor1.topics { ... }
Or if you want to attach a message to a sensor you could do something like this (don't forget to properly add the newly created object to the DB first):
let message1 = Message()
message1.stringValue = "Some text"
sensor2.messages.append(message1)
So, no need to use intermediary Swift Arrays.

Answer 2

After testing I managed to add another array like that:
class Sensors : Object {
dynamic var type = ""
dynamic var name = ""
dynamic var badge = 0
var topic: [String] {
get {
return topicV.map { $0.stringValue }
}
set {
topicV.removeAll()
topicV.append(objectsIn: newValue.map({ RealmString(value: [$0]) }))
}
}
var message: [String] {
get {
return messageV.map { $0.stringValue1 }
}
set {
messageV.removeAll()
messageV.append(objectsIn: newValue.map({ RealmString1(value: [$0]) }))
}
}
let topicV = List<RealmString>()
let messageV = List<RealmString1>()
override static func ignoredProperties() -> [String] {
return ["topic", "message"]
}
}
class RealmString: Object {
dynamic var stringValue = ""
}
class RealmString1: Object {
dynamic var stringValue1 = ""
}

Answer 3

What bogdanf has said, and the way you've implemented it are both correct.
Basic value types aside, Realm can only store references to singular Realm Object objects, as well as arrays of Objects using the List type. As such, if you want to save an array of types, it's necessary to encapsulate any basic types you want to save (like a String here) in a convenience Realm Object.
Like bogdanf said, it's not recommended to convert Realm Lists to standard Swift arrays and back again, since you lose the advantages of Realm's lazy-loading features (which can cause both performance and memory issues), but memory issues can at least be mitigated by enclosing the code copying data out of Realm in an #autoreleasepool block.
class MyObject: Object {
dynamic var childObject: MyObject?
let objectList = List<MyObject>()
}
So in review, it's best practice to work directly with Realm List objects whenever possible, and to use #autoreleasepool any time you do actually want to loop through every child object in a Realm. :)