Trying to create a Swift Realm Data Model - ios

Question

I have looked at the Realm.io docs. I am working on an application to track my vehicle expenses. I have put together what I think might work for a data model in Realm, but I am new to it and not sure if this is something that will work or if there is a better way to do it. Here is what I have, and I have not put this in a project and tried to compile yet. The realm.io docs are a little vague to me, so maybe someone can tell me what you think. I have included some comments in places that I am just not sure how to achieve what I'm going for...
// Vehicle model
class Vehicle : RLMObject {
dynamic var name = “”
dynamic var number = “”
dynamic var currentMiles = 0
dynamic var entries = RLMArray(objectClassName: Entry.className())
}
// Entry model
class Entry: RLMObject {
dynamic var vehicle: Vehicle //??
dynamic var date = NSDate()
dynamic var expense = 0.0
dynamic var mileage : Vehicle.currentMiles // want to update the Vehicle mileage with each entry
}
// Gas model
class Gas: Entry {
dynamic var gallons = 0
dynamic var pricePerGallon = 0.0
}
// OilChange model
class OilChange : Entry {
dynamic var milesBetweenChanges = 0
}
// Other Service model
class OtherService: Entry {
dynamic var notes = “”
}

Answer 1

You're on the right track! The only model that needs work is Entry, I think. First, here's your model with my annotations:
// Entry model
class Entry: RLMObject {
dynamic var vehicle: Vehicle // This is valid Swift, but you'll need to set the value in the designated initializer (`init()`).
dynamic var date = NSDate()
dynamic var expense = 0.0
dynamic var mileage : Vehicle.currentMiles // This isn't valid Swift, since `Vehicle` is a class, and doesn't have a `currentMiles` member
}
What you want is something like this:
// Entry model
class Entry: RLMObject {
dynamic var vehicle = Vehicle() // Use a default value so that `init()` succeeds, but you can still use `init(vehicle: Vehicle)` in your code
dynamic var date = NSDate()
dynamic var expense = 0.0
dynamic var mileage = 0
init() {
// Must override init() when adding a convenience initializer
super.init()
}
convenience init(vehicle: Vehicle) {
super.init()
self.vehicle = vehicle
mileage = vehicle.currentMiles
}
}
It's unfortunate that you find Realm's docs vague. Please let us know if there's anything in particular you'd like us to clarify. We're a pretty approachable bunch!