Hello Zaid, I don't know what prevents you from implementing your DAOs.
For an example of a library that uses them extensively, see http://github.com/groue/GRDB.swift: struct PointOfInterest { var id: Int64? var title: String? var favorite: Bool var coordinate: CLLocationCoordinate2D } // (snip) adopt protocols that turn PointOfInterest in a "record" // Fetch from SQL let pois = try PointOfInterest.fetchAll(db, "SELECT * FROM pointOfInterests") // [PointOfInterest] // Fetch without SQL let title = Column("title") let favorite = Column("favorite") let poi1 = try PointOfInterest.fetchOne(db, key: 1) // PointOfInterest? let pois = try PointOfInterest.fetchOne(db, keys: [1, 2, 3]) // [PointOfInterest] let paris = try PointOfInterest.filter(title == "Paris").fetchOne(db) // PointOfInterest? let favoritePois = try PointOfInterest // [PointOfInterest] .filter(favorite) .order(title) .fetchAll(db) // Insert, update, delete var berlin = PointOfInterest( id: nil, title: "Berlin", favorite: false, coordinate: CLLocationCoordinate2DMake(52.52437, 13.41053)) try berlin.insert(db) berlin.id // some value berlin.favorite = true try berlin.update(db) try berlin.delete(db) GRDB "records" work pretty well with structs, but also class hierarchies, without any caveat. Can you explain a little more your issue ? Gwendal Roué > Le 2 juin 2017 à 11:18, Zaid Daghestani via swift-evolution > <swift-evolution@swift.org> a écrit : > > Greetings Swift Community, > > Today I’m throwing out a pitch on freeing the shackles on Self. Self is a > potentially significant tool that I am itching to implement in my patterns to > make my code more concise, clear and intuitive. > > Self, by far, is cherished by Data Models and ORM's, and particularly DAO > <https://en.wikipedia.org/wiki/DAO> s (Ref. 1 for examples). There are a > significant amount of patterns in which a base class’s methods are Self > relevant and not generic relevant. Self being non-referrable in non-nominal > types denies significant feature and pattern delivery such as DAO. And to > deny implementation of a pattern as significant as DAO’s seems like a shot in > the foot. Adding Self to non-nominal types brings Collections and Async to > our class/protocol methods. A single query method returning a sync or likely > async collection on my DataModel class will be used in about 80% of my app > screens and 80% of my eerver API’s, almost all of the time. Hell this even > applies to struct patterns as well. > > Now, DAO’s can actually already currently be achieved via generics, see Ref. > 2. This actually still a pretty good implementation, but Self is a > significantly more true implementation of these patterns. Issues with the > current generic pattern of Self relevancy in Swift is: > 1- Generic methods in the base class are a workaround to the lack of Self. > The base class is not a class that implements generic patterns. It a base > class that implements Self patterns. Self is more concise and intuitive in > implementing a DAO or any other Self relevant base class. > 2- Self relevant patterns are distinct and not the same as Generic patterns. > 3- In usage of a DAO, the generic pattern requires that the Left Hand Side be > typed to collapse the generic. In the case of Self relevance, the particular > class name is enough. Swift, being an inference language, would be truer with > the Self system, and not the repetitive type declaration style of ObjC/Java > that generics provide. > let friends = User.where("id IN %@", friendIds) // truer to Swift type > inference > // vs. > let friends:[User] = User.where("id IN %@", friendIds) // Java/Objective-C > style repetitive type declarations > > Let’s break the chains on Self! It is extremely intuitive, and we are all > going to use it > > Peace! > > Z > > > > > Ref 1: DAO patterns:: > > class DataModelObject { > > /* One of the most significant use cases > * Retrieving a queried on collection asynchronusly > */ > class func `where`(_ predicate:String, _ args:CVarArg...) -> > Promise<[Self]> { > // querie > return Promise(value: [[]) > } > > // some more examples > > // optional async get > class func get(id:String) -> Promise<Self?> { > return Promise(value:self.init(id:id)) > } > > // sync all collection > class func all() -> [Self] { > return [] > } > // asynnchronous fetch > class func allAsync() -> Promise<[Self]> { > return Promise(value: []) > } > > // in the case of RealmDB we have returns of Results<Self>, a lazy > collection > class func `where`(_ predication:NSPredicate) -> Results<Self> { > return Results<self>() > } > } > > class User : DataMadelObject { > dynamic var id:String = "" > dynamic var name:String = "" > } > > let friendIds = [1, 2, 3] > let friends = User.where("id IN %@", friendIds) > > Ref 2: Currently implementable DAO > > class DataModelObject { > > /* One of the most significant use cases > * Retrieving a queried on collection asynchronusly > */ > class func `where`<T: DataModelObject>(_ predicate:String, _ > args:CVarArg...) -> Promise<[T]> { > // querie > return Promise(value: []) > } > > // some more examples > // optional async get > class func <T: DataModelObject>get(id:String) -> Promise<T?> { > return Promise(value:self.init(id:id)) > } > > > // sync all collection > class func all<T: DataModelObject>() -> [T] { > return [] > } > // asynnchronous fetch > class func allAsync<T: DataModelObject>() -> Promise<[T]> { > return Promise(value: []) > } > > // in the case of RealmDB we have returns of Results<Self>, a lazy > collection > class func `where`<T: DataModelObject>(_ predication:NSPredicate) -> > Results<T> { > return Results<T>() > } > } > > class User : DataMadelObject { > dynamic var id:String = "" > dynamic var name:String = "" > } > > let friendIds = [1, 2, 3] > let friends:[User] = User.where("id IN %@", friendIds) > > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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