"Correct" Realm Models in swift? [closed] - swift

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I'm currently implementing my first app in swift, which uses Realm. I really like it! However, I tried to make my models "good" but I really feel I made them worse for realm. Here's an example model:
import RealmSwift
class Location : Object {
dynamic var ident = ""
dynamic var package = ""
dynamic var title = ""
dynamic var is_selected = false
let contentSets = List<ContentSet>()
convenience init(ident : String, package: String, title : String, is_selected : Bool) {
self.init()
self.ident = ident
self.package = package
self.title = title
self.is_selected = is_selected
}
override static func primaryKey() -> String? {
return "ident"
}
func save() {
let realm = try! Realm()
try! realm.write {
realm.add(self)
}
}
static func findAll() -> Results<Location> {
return try! Realm().objects(Location)
}
static func findByIdent(ident : String) -> Location?{
return try! Realm().objects(Location).filter("ident == %#", ident).first as Location?
}
static func getSelected() -> Location? {
return try! Realm().objects(Location).filter("is_selected == true").first as Location?
}
func hasContentSetByObject(contentSet : ContentSet) -> Bool {
return self.hasContentSetByString(contentSet.ident)
}
func addContentSet(contentSet: ContentSet) {
let realm = try! Realm()
try! realm.write {
self.contentSets.append(contentSet)
}
}
func isSelected(value: Bool) {
let realm = try! Realm()
let selectedLocation = Location.getSelected()
selectedLocation?.isSelected(false)
try! realm.write {
self.is_selected = value
try! realm.commitWrite()
}
}
func hasContentSetByString(ident : String) -> Bool {
let result = self.contentSets.filter{$0.ident == ident}.count > 0 ? true : false
return result
}
}
My idea was, to keep everything realm related out of my controllers. However, in regards to update data on the models this approach is bad I feel, because it erases a lot of Realm's flexibility.
How are you guys doing that sort of stuff? Looking forward to your input.
Regards,
SantoDE

Answer 1

You can preserve your "separation of concerns" without having to sacrifice the whole rationale behind Realm's transactional mutation model, or the internals of its querying syntax.
Here are a few tips:
1. Minimize the number of areas where you need to do error handling.
From your small sample, there are 10 failable calls (try!) with no error handling. This is a code smell. As in, not necessarily incorrect, but should make you take a closer look and reconsider the pattern.
Even if you were handling errors in each case, that would be tedious and error-prone.
Instead, why not keep the error handling as localized as possible, yielding simpler code, less duplication and less opportunity for unhandled errors?
You can do this by using dependency injection, lifting the Realm instance out of the model methods, and passing the Realm instance to the parts of your code that need it.
2. Avoid redundant type casts
Realm Swift makes heavy use of Swift's generics system, yielding dynamic casts like this one redundant:
try! Realm().objects(Location).filter("ident == %#", ident).first as Location?
Because the following is even more type safe, since there's no opportunity to use the wrong type:
try! Realm().objects(Location).filter("ident == %#", ident).first
3. Avoid redundant write commits
this code:
try! realm.write {
self.is_selected = value
try! realm.commitWrite()
}
is incorrect, since a Realm.write(_:) invocation automatically calls Realm.commitWrite() after invoking the passed-in closure. So just replace with this:
try! realm.write {
self.is_selected = value
}
4. Avoid leaving Realm's query system
Code like this forces Realm to materialize all its objects as Swift objects, which performs very poorly:
let result = self.contentSets.filter{$0.ident == ident}.count > 0 ? true : false
return result
Instead, you should prefer Realm's native querying system, which is optimized for Realm data:
return !contentSets.filter("ident == %#", ident).isEmpty
In general, I'd also say that if you find yourself writing lots of code in the name of separation of concerns, what are you really gaining?