I want to use Realm to my iOS app but I have a problem with the relationship. What I want to achieve is a relationship between the following two RLMobjects :
class Catalogue: RLMObject {
dynamic var ID = ""
dynamic var greekName = ""
dynamic var deutschName = ""
dynamic var createdAt = NSDate()
dynamic var updatedAt = NSDate()
override class func primaryKey() -> String? {
return "ID"
}
}
class Products: RLMObject {
dynamic var foodName = ""
dynamic var foodDescription = ""
dynamic var foodPrice = ""
dynamic var createdAt = NSDate()
dynamic var updatedAt = NSDate()
dynamic var category: Catalogue?
}
I am retrieving all my data from a server in JSON format and the problem is that
I can not set the category as relationship to Catalogue ID.
In my database the category field is a foreign key to the Catalogue ID.
Does anyone knows how can I do that in Realm?
Thank you in advance.
Rather than storing the Catalogue ID in the dynamic var category: Catalogue? relationship field you will need to find the Catalogue object and just store that directly. This is how you link objects and is an important and powerful part of using NoSQL type DB's like Realm.
I would also add an array of products relationship on Catalogue so that you can link all the products to the Catalogue itself.
You can see more discussion about this here if that wasn't fully clear. Hope this helps
Related
I have a data coming from webservice. I have same models made in my project. To demonstrate the model let me show a little idea of my model
Model1:
class Standard {
var Id = 0
var standardName = ""
var students : [StudentModel] = nil
}
Model2:
class StudentModel {
var Id = 0
var stdName = ""
var Teacher: [TeacherModel] = nil
}
Model3:
class TeacherModel {
var Id = 0
var Name = ""
}
Now what I am facing is as follow :
I have TeacherModel in DB already, but I dont have student model and standard model instance int he Realm, so it is supposed to save coming student and standard data in Realm. and skip or update TeacherModel in Realm. But right now it is crashing on TeachModel data as one Teacher with same things are already saved in Realm.SO i am looking forward to some sort of method in which it update or just skip saving Item if already exist in the Realm.
Note: These models are just to demonstrate my case, where as I know there are many typos and other thing. Also I did not showed any implementation of Realm over my Models. Its just to show you the things to make you understand.
Well you need to have class func primaryKey() -> String? overriden.
override class func primaryKey() -> String? {
return "Id"
}
And then use realm.write(...) or realm.create(...) functions with update parameter set to true.
I have two models, lets call them Schools, and Teachers. Models are as under
#objcMembers public class Schools : Object {
dynamic var Id : String = ""
dynamic var UserId : Int64 = 0
dynamic var Name : String? = ""
dynamic var listTeachers : List<Teachers>? = nil
dynamic var teachersList : [Teachers]? = []
}
#objcMembers public class Teachers : Object {
dynamic var Id : String = ""
dynamic var UserId : Int64 = 0
dynamic var Name : String? = ""
}
now before saving data I m putting Teachers objects (list) in School object then I save that School object in realm write closure.
after that I just get the School realm object and when I get the Teachers list, it always gets Nil. What is the case?
Am i missing something or missing something to understand the real LIST property??
please help
Update: This is how I am getting object
let mSavedItems = mDbHelper.realmObj.objects(Schools.self)
if let teachers = mSavedItems[0].teachersList{// here teacher list is nil
}
Your Schools declaration is flawed. You shouldn't declare a List as dynamic or mutable, nor should you make it Optional. As the docs clearly state, let listTeachers = List<Teachers>() is the correct way to declare a many-to-many relationship.
Storing a property of type Array is also not supported by Realm, so you should delete the teachersList : [Teachers]? property.
#objcMembers public class Schools : Object {
dynamic var Id : String = ""
dynamic var UserId : Int64 = 0
dynamic var Name : String? = ""
let listTeachers = List<Teachers>()
}
I am new to realm and iOS development so I apologize in advance if something isn’t explained properly or is just incorrect.
I have 2 Realm Object classes:
class Category: Object {
#objc dynamic var name: String = ""
#objc dynamic var color: String = ""
let trackers = List<Tracker>()
}
and
class Tracker: Object {
#objc dynamic var timeSegment: Int = 0
var parentCategory = LinkingObjects(fromType: Category.self, property:
"trackers")
}
I’m able to store new timeSegment properties consistently; however, the issue is that I cannot retrieve & display a collection of timeSegment values relating to their parentCategory. setting
var entries : Results<Tracker>?
produces all results for every category, which is the only result i'm able to pull so far after testing.
Any help is appreciated, and can follow up with any additional details. Thanks
You need to call objects on your Realm object with a filter for fetching only results that match a predicate. The realm object in this code is an instance of the Realm class.
func getTrackersWithName(_ name: String) -> Results<Tracker> {
return realm.objects(Tracker.self).filter("name = \"\(name)\"")
}
This tells Realm to fetch all objects that match the filter predicate. In this case, the filter predicate matches any object where the value of the "name" property matches the string that is passed into the method.
I'm new to iOS development and currently using Realm as database. My first tableview display Restaurant object and second table display customer objects. How can i link this two objects?. Means when i click each restaurant it will display different customer.
class Restaurant: Object {
dynamic var restname: String = ""
dynamic var date: String = ""
}
class Customer: Object {
dynamic var id = 0
dynamic var name: String = ""
dynamic var price: Float = 0.0
dynamic var drinks: Float = 0.0
override static func primaryKey() -> String? {
return "id"
}
}
You make references to your models like so
class Customer: Object {
dynamic var restaurant: Restaurant?
}
You also have the possibility to get reverse relationship with LinkingObjects(fromType:, property:)
You can write in your other model
class Restaurant: Object {
let customers = LinkingObjects(fromType: Customer.self, property: "restaurant")
}
That way you don't duplicate relationships.
If I understand, in Restaurant class put this:
dynamic var _customer = Optional(Customer())
or in Customer class put this line:
dynamic var _restaurant = Optional(Restaurant())
NOTE: Name of variable with lower dash, may be any name, my habit is to put lower dash
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 = “”
}
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!