Using Realm in Swift (I am still using the version just before v1.x):
I have this class
class Event: Object {
dynamic var id: String = ""
dynamic var title: String? = nil
dynamic var creator: User?
let members = List<User>()
}
How can I find all events with the member "User A" (I have the id of the User A).
I tried something like this but doesn't really work:
let predicate = NSPredicate(format: "ANY members.id == %#", userA.id)
eventsWithUserA = realm.objects(Event).filter(predicate)
If you're not using the latest version, hopefully you're at least using version 0.100 or higher. If so, you can use Realm's inverse relationships feature to do this:
class User: Object {
let events = LinkingObjects(fromType: Event.self, property: "members")
}
After implementing this, user.events will return a List of every Event object in which the user object is in its members property.
let eventsWithUserA = userA.events
Hopefully this should eliminate the entire need to manually perform a query for what you're trying to achieve here.
Let me know if that doesn't work for you!
Related
I'm brand new to this, so forgive me if I'm missing something obvious or not asking the right question. I plan to make an app that have a few sets of data that require many-to-many relationships. For example, if I have a model for Food items and a model for CookingMethods to cook that food item. So, each Food can have multiple CookingMethods, and each CookingMethod applies to multiple types of Food.
I think this is the right way to set up the realm data:
class Food: Object {
#objc dynamic var title: String = ""
#objc dynamic var id: Int = 0
var cookingMethods = List<CookingMethod>()
}
class CookingMethod: Object {
#objc dynamic var id: Int = 0
#objc dynamic var title: String = ""
let foods = LinkingObjects(fromType: Food.self, property: "cookingMethods")
}
Is it now possible to import a set of data (probably a csv file?) using either Realm Studio or programmatically that allows me to link this relationship? The Food would have a list of CookingMethods, and the CookingMethods would link back to multiple different Foods?
If I'm going about this all wrong please let me know, there is a spreadsheet of data that I'd like to add to my app's database as a one time thing.
I am getting this error and can't seem to find any answer anywhere online. It is Swift 5.1 and Realm 3.19.1
Querying over backlinks is disabled but backlinks were found in the inverse relationship
I have two simple Realm Model objects, Todo and User.
#objcMembers class User: Object {
dynamic var uid: String! = UUID().uuidString
dynamic var username: String?
dynamic var added: Date = Date() // Date when user is added
let todos = List<Todo>()
}
And:
#objcMembers class Todo: Object {
dynamic var title: String!
dynamic var added = Date()
let user = LinkingObjects(fromType: User.self, property: "todos")
}
And here I am calling the Todo objects:
var todos = realm.objects(Todo.self).filter("ANY user.uid CONTAINS [c]%#", uid)
Is there something I am doing wrong? Or somehow backlinks need to be activated somewhere before I can use them?
Realm documentation is of absolutely no help whatsoever.
What I am trying to do is to query all todo items for a given user by user id. Each User object has a list of Todo objects in it.
I'm creating an app that interacts with a Firestore database. As of now I have a singleton class, DatabaseManager that has all the methods relating to the Firestore database (i.e. get/post methods).
I have a User model called User that has properties such as name, email, photoURL, and some app-specific properties. Any user can edit their profile to update information from a view controller called EditProfileViewController.
Now my question is: is it best to call the DatabaseManager.shared.updateInfo(forUser: user) (where user is a User instance) from EditProfileViewController, User, or some other place?
Sorry if this is an obvious question, but there's going to be a lot of points in the app where I'll need similar logic so I wanted to know what's the best design. Also I'm sure this question has more to with MVC than it does Firebase/Swift.
A couple of thoughts:
Rather than accessing the singleton directly with, DatabaseManager.shared.update(for:), I might instead have a property for the database manager, initialize/inject it with the DatabaseManager.shared, and have whatever needs to interact with the database use that reference, e.g., dataManager.update(for:). The goal would be to allow your unit tests to mock a database manager if and when necessary.
I would not be inclined to have a view controller interact directly with the DatabaseManager. Many of us consider the view controller, which interacts directly with UIKit/AppKit objects, as part of the broader “V” of MVC/MVP/MVVM/whatever. We’d often extricate business logic (including interaction with the database manager) out of the view controller.
I personally wouldn’t bury it under the User object, either. I’d put it in an extension of the database manager, and called from the view model, the presenter, or whatever you personally want to call that object with the business logic.
Is there a reason you're using a singleton to contain all the Firestore logic? User model should contain the method updateInfo.
Here's an example i've used with Firestore:
class Group {
// can read the var anywhere, but an only set value in this class
private(set) var groupName: String!
private(set) var guestsInGroup: Int!
private(set) var joinedGroup: Bool!
private(set) var timeStampGroupCreated: Date!
private(set) var documentId: String!
init(groupName: String, guestsInGroup: Int, joinedGroup: Bool, timeStampGroupCreated: Date, documentId: String) {
self.groupName = groupName
self.guestsInGroup = guestsInGroup
self.joinedGroup = joinedGroup
self.timeStampGroupCreated = timeStampGroupCreated
self.documentId = documentId
}
// method to parse Firestore data to array, that table view will display
class func parseData(snapshot: QuerySnapshot?) -> [Group]{
var groups = [Group]()
guard let snap = snapshot else { return groups }
for document in snap.documents {
let data = document.data()
let groupName = data[GROUP_NAME] as? String ?? "No Group Name"
let guestsInGroup = data[GUESTS_IN_GROUP] as? Int ?? 0
let joinedGroup = data[JOINED_GROUP] as? Bool ?? false
let timeStampGroupCreated = data[TIMESTAMP_GROUP_CREATED] as? Date ?? Date()
let documentId = document.documentID
// add objects with fetched data into thoughts array
let newGroup = Group(groupName: groupName, guestsInGroup: guestsInGroup, joinedGroup: joinedGroup, timeStampGroupCreated: timeStampGroupCreated, documentId: documentId)
groups.append(newGroup)
}
return groups
}
}
In a swift IOS app I have a Realm Model like this:
import Foundation
import RealmSwift
class Item: Object {
dynamic var name = ""
let prices = List<Price>()
}
This lets me save an instance of Item with an empty String as a name:
let newItem = Item()
newItem.name = "" //or not set the attribute at all
let realm = Realm()
realm.write {
realm.add(newItem)
}
How can I setup simple (and more complex) attribute validation?
The name String is supplied from an UITextField. Do I do validate the user input in the ViewController responsible here, or is there a way to do this on the Realm Model, like the rails developer in me wants to do?
Thanks in advance.
Cheers,
nc
Realm currently does not support validation beyond uniqueness for primary keys, but you can follow https://github.com/realm/realm-cocoa/issues/1769 for further updates!
In Swift is it possible to retrieve / remove an element in a Dictionary using it's index, not a key value? In this example I'm attempting to create a "to do" list where I can eventually access all the tasks assigned to an individual. But I would also like to remove an element (task) by index.
In the code below how can I remove the second task "wash dishes" by index not using a key value. I was hoping to call this func with something like: taskMgr.removeTaskByIndex(1)
Any additional explanation or advice is helpful as I'm just learning Swift.
import Foundation
class TaskManager{
var taskDictArray = Dictionary<String, String>()
init(){
taskDictArray = [:]
}
func addTask(task: String, person: String){
taskDictArray[task] = person
}
}
var taskMgr = TaskManager()
taskMgr.addTask("take out trash", person: "emma")
taskMgr.addTask("wash dishes", person: "jack")
taskMgr.addTask("clean floor", person: "cleo")
//taskMgr.removeTaskByIndex(1)
//var a = taskMgr.getTaskByIndex(1)
Dictionaries do not maintain their object order and the only way to get a value is using its key. You'll probably want to associate whatever list of tasks you have the index for with its corresponding key and use that manipulate the dictionary. This is the only way. You probably consider restructuring your application logic if it's impossible.
You'll need to add a function such as
func removeTask(task: String) {
taskDictArray[task] = nil
}
So find a way to get the actual task string with which you are associating it.