I have defined two very basic Object as follows:
class Language: Object {
dynamic var id: String = "" //"english", "chinese"
let versions = List<Version>()
convenience init(id: String, versions: [Version]) {
self.init()
self.id = id
self.versions.append(objectsIn: versions)
}
override static func primaryKey() -> String? {
return "id"
}
}
class Version: Object {
dynamic var id: String = "" //"kjv", "cus"
dynamic var name: String = "" //"Union Simplified"
let language = LinkingObjects(fromType: Language.self, property: "versions")
convenience init(id: String, name: String) {
self.init()
self.id = id
self.name = name
}
override static func primaryKey() -> String? {
return "id"
}
}
Every Language can have multiple Versions, and every Version has a reference (LinkingObject) to what Language holds it.
Next, I have the following code:
let kjvVersion = Version(id: "kjv", name: "King James Version")
let englishLanguage = Language(id: "english", versions: [kjvVersion])
print(kjvVersion)
Inspecting kjvVersion.language gives me back an empty LinkingObject array. Why?! What am I doing wrong here?
LinkingObjects objects contain the objects in the Realm which link to the containing object. Your objects are not managed by a Realm, so there will never be any objects in a Realm which link to them.
Related
I have a JSON hosted somewhere and I want to fetch the content, put it in a context for my leaf template to read.
However, I cannot make it work. I get the code to compile, but I get an error in the localhost
{"error":true,"reason":"Unsupported Media Type"}
Can somebody help me please! Happy holidays for all.
struct WebsiteController: RouteCollection {
func boot(routes: RoutesBuilder) throws {
routes.get(use: indexHandler)
}
func indexHandler(_ req: Request) -> EventLoopFuture<View> {
return req.client.get("https://streeteasydaily.s3.us-west-2.amazonaws.com/streeteasy1.json").flatMap { res in
do {
let json = try res.content.decode([Listing].self)
print(json[0].photos[0])
let context = IndexContext(title: "Homepage", listings: json)
return try req.view.render("index", context)
} catch {
// Handle error
print("cayo en error")
return req.eventLoop.makeFailedFuture(error)
}
}
}
}
struct IndexContext: Encodable {
let title: String
let listings: [Listing]
}
Model
final class Listing: Model {
static let schema = "listings" //basically the table name
#ID
var id: UUID?
#Field(key: "address")
var address: String
#Field(key: "description")
var description: String
#Field(key: "photos")
var photos: [String]
init() {}
//to initialize the db
init(id: UUID? = nil, address: String, description: String, photos: [String]) {
self.id = id
self.address = address
self.description = description
self.photos = photos
}
}
//to make acronym conform to CONTENT, and use it in Vapor
extension Listing: Content {}
This error is because the decode is failing to identify all the fields in your JSON to match against those defined in Listing and/or the array of such objects. The filenames must match those in the JSON exactly - i.e. case-sensitive and every field in the structure/model must exist in the JSON. Additional fields in the JSON that are not needed/included in the structure/model are fine.
I am attempting to implement a GKGameModel in my application. In it, it holds variables to a few things, but for the purposes of my question I'm interested in the following two variables:
import GameplayKit
final class GameModel: NSObject, GKGameModel {
var players: [GKGameModelPlayer]?
var activePlayer: GKGameModelPlayer?
}
I do something like this to initialise the game with 3 players (not exact)
let game = GameModel.init()
game.players = [Player(),Player(),Player()] // Create 3 players
guard let firstPlayer = game.players.first else {
return
}
game.activePlayer = firstPlayer
A player class is defined as:
class Player : NSObject, GKGameModelPlayer {
var playerId: Int // GKGameModelPlayer protocol variable
let name: String
var cash: Int = 0
}
In my project I have Realm Entities and the models seperated. So there will be a PlayerEntity and a Player class.
I'm wanting to use RealmSwift to save and load the GKGameModelPlayer data, and more specifically the ability to store/re-store the active player.
I think the key here is the playerId variable; but I am not sure.
But what I'm not sure about is retrieving this information and then re-mapping it into a valid GKGameModelPlayer format
My current idea/theory is that I need to map my model to an entity class and vice-versa.
Ie:
// [REALM] Player entity
class PlayerEntity: Object {
#objc dynamic var id = UUID().uuidString
#objc dynamic var playerId: Int = 0
#objc dynamic var name: String = ""
#objc dynamic var cash: Int = 0
override static func primaryKey() -> String {
return "id"
}
}
And then I extend this class to do some "mapping":
extension PlayerEntity {
// Map model -> entity
convenience init(model: Player) {
self.init()
self.playerId = model.playerId
self.name = model.name
self.cash = model.cash
}
}
extension Player {
// Map entity -> model
convenience init(entity: PlayerEntity) {
let playerId = entity.playerId
let name = entity.name
let cash = entity.cash
self.init(id: playerId, name: name, cash: cash)
}
}
Right now, the playerId is always zero (0) because I'm not really sure how to set it.
I can save a player to realm.
The issue comes from when I try to restore the player, and I want to restore the activePlayer variable in the GameModel
Therefore, my question is:
How would I go about saving and restoring the activePlayer variable so that it continues to comply to GKGameModelPlayer?
I appreciate any assistance on this.
With thanks
While you could use those extensions, sometimes simpler is better. Here's a rough example:
class PlayerEntity: Object {
#objc dynamic var playerId: Int = 0
#objc dynamic var name: String = ""
#objc dynamic var cash: Int = 0
convenience init(withPlayer: PlayerClass) {
self.init()
self.playerId = withPlayer.playerId
self.name = withPlayer.name
self.cash = withPlayer.cash
}
func getPlayer() -> Player {
let p = Player()
p.playerId = self.playerId
p.name = self.name
p.cash = self.cash
return p
}
override static func primaryKey() -> String {
return "playerId"
}
}
to load all the players into an array... this will do it
let playerResults = realm.objects(PlayerEntity.self)
for player in playerResults {
let aPlayer = player.getPlayer()
self.playerArray.append(aPlayer)
}
Notice the removal of
#objc dynamic var id = UUID().uuidString
because it's not really being used to identify the object as a primary key.
The primary key is really
var playerId: Int // GKGameModelPlayer protocol variable
which is fine to use as long as it's unique.
I have the following (simplified) Realm Models:
final class Item: Object {
#objc dynamic var identifier: String = ""
#objc dynamic var programSet: ProgramSet?
override static func primaryKey() -> String? {
return "identifier"
}
}
final class ProgramSet: Object {
#objc dynamic var identifier: String = ""
#objc dynamic var editorialCategory: EditorialCategory?
override static func primaryKey() -> String? {
return "identifier"
}
}
final public class EditorialCategory: Object {
#objc dynamic var identifier: String = ""
override public static func primaryKey() -> String? {
return "identifier"
}
}
final class Playlist: Object {
#objc dynamic var id = UUID().uuidString
#objc dynamic var name = ""
#objc dynamic var created = Date()
var items = List<Item>()
override static func primaryKey() -> String? {
return "id"
}
}
When the user adds an item to a playlist, I try to append the ItemModel to the Playlist.items List:
try realm.write {
playlistToModify.items.append(item)
}
My problem is that it's possible for Items to share the same EditorialCategory, so it may already be in the database. When I add other items via the Realm.add(_:update:) method, Realm won't try to recreate the linked objects if one with the same primary key exists.
The List.append(_:) method seems to force recreating the linked objects of an ItemModel when called. The app crashes in the following line from object_accessor.hpp:
throw std::logic_error(util::format("
Attempting to create an object of type '%1' with an existing primary key value '%2'.",
object_schema.name, ctx.print(*primary_value)));
Stacktrace:
The object_schema.name is "EditorialCategoryModel", which is linked in ProgramSetModel, which itself is linked from ItemModel.
Is there a way to avoid this error and append the item to the list without Realm attempting to re-create every linked object? Thanks!
public class User : NSObject {
var id: Int //will throw an error during build
var name: String?
override init(){
}
convenience init(id: Int, name: String?){
self.id = id
self.name = name
}
}
I want to create a user class. The id should non-optional. However, my above code does not work unless I change the line to:
var id: Int = 0
I don't want to do this. Is there a better way?
Delete the word convenience! Convenience is exactly the opposite of what you want. You want this to be a designated initializer. Like this:
public class User : NSObject {
var id: Int
var name: String?
init(id: Int, name: String?){
self.id = id
self.name = name
super.init()
}
}
This forces the creator of a User to supply an id, which is exactly what you want.
public class User {
let id: Int
var name: String?
init(id: Int, name: String? = nil) {
self.id = id
self.name = name
}
}
let user = User(id: 3) // works without errors
As you can see, I changed some things. You probably don't really need to subclass NSObject, and I don't think you'll want to change a user's id after initialisation, so it makes more sense to make it a let constant.
I have a custom class in Swift and I'd like to use subscripting to access its properties, is this possible?
What I want is something like this:
class User {
var name: String
var title: String
subscript(key: String) -> String {
// Something here
return // Return the property that matches the key…
}
init(name: String, title: String) {
self.name = name
self.title = title
}
}
myUser = User(name: "Bob", title: "Superboss")
myUser["name"] // "Bob"
Update: The reason why I'm looking for this is that I'm using GRMustache to render from HTML templates. I'd like to be able to just pass my model object to the GRMustache renderer…
GRMustache fetches values with the keyed subscripting objectForKeyedSubscript: method and the Key-Value Coding valueForKey: method. Any compliant object can provide values to templates.
https://github.com/groue/GRMustache/blob/master/Guides/view_model.md#viewmodel-objects
This is a bit of a hack using reflection. Something along the lines of the following could be used.
protocol PropertyReflectable { }
extension PropertyReflectable {
subscript(key: String) -> Any? {
let m = Mirror(reflecting: self)
for child in m.children {
if child.label == key { return child.value }
}
return nil
}
}
struct Person {
let name: String
let age: Int
}
extension Person : PropertyReflectable {}
Then create a Person and access it's keyed properties.
let p = Person(name: "John Doe", age: 18)
p["name"] // gives "John Doe"
p["age"] // gives 18
You could modify the subscript to always return an interpolated string of the property value.
Adding some syntax sugar to Benzi's answer:
protocol PropertyReflectable { }
extension PropertyReflectable {
subscript(key: String) -> Any? {
let m = Mirror(reflecting: self)
return m.children.first { $0.label == key }?.value
}
}
struct Person: PropertyReflectable {
let name: String
let age: Int
}
Then create a Person and access it's keyed properties.
let p = Person(name: "John Doe", age: 18)
p["name"] // gives "John Doe"
p["age"] // gives 18
Using valueForKey should enable you to access properties using their names. Be sure that you're working with a object that inherit NSObject
class people: NSObject {
var age: NSString = "44"
var height: NSString = "153"
}
let person:people = people()
let stringVariable = "age"
person.valueForKey("age")
// Print "44"
person.valueForKey("\(stringVariable)")
// Print "44"
(GRMustache author here)
Until a swift-oriented Mustache library is out, I suggest having your classes inherit from NSObject (so that they have the valueForKey: method). GRMustache will then fetch values with this method.
In case this would still not work (blank values in the rendering), you may try to disable GRMustache security features (see https://github.com/groue/GRMustache/blob/master/Guides/security.md#disabling-safe-key-access)
Should you experience any other trouble, please open an issue right into the repository: https://github.com/groue/GRMustache/issues
EDIT February 2, 2015: GRMustache.swift is out: http://github.com/groue/GRMustache.swift
Shim's answer above doesn't work anymore in Swift 4. There are two things you should be aware of.
First of all, if you want to use value(forKey:) function, your class must inherit NSObject.
Secondly, since Objective-C doesn't know anything about value type, you have to put the #objc keyword in front of your value type properties and Swift will do the heavy-lifting for you.
Here is the example:
import Foundation
class Person: NSObject {
#objc var name: String = "John Dow"
#objc var age: Int = 25
#objc var height: Int = 180
subscript(key: String) -> Any? {
return self.value(forKey: key)
}
}
let person: Person = Person()
person["name"] // "John Dow"
person["age"] // 25
person["height"] // 180
I suppose you could do:
class User {
let properties = Dictionary<String,String>()
subscript(key: String) -> String? {
return properties[key]
}
init(name: String, title: String) {
properties["name"] = name
properties["title"] = title
}
}
Without knowing your use case I would strongly advise against doing this.
Another approach:
class User {
var name : String
var title : String
subscript(key: String) -> String? {
switch key {
case "name" : return name
case "title" : return title
default : return nil
}
}
init(name: String, title: String) {
self.name = name
self.title = title
}
}
It might be worth noting that Swift doesn't appear to currently support reflection by names. The reflect function returns a Mirror whose subscript is Int based, not String based.