I need to save some data with CoreData. Generally thats not a problem at all. The problem is, that the data is created with EVReflection an therefore inherits the class EVObject. To save the gathered data to CoreData they have to also inherit NSManagedObject. The problem is that swift does not allow you to inherit multiple classes. Would appreciate any tips.
class Device : EVObject
{
var channel : [Channel] = [Channel]()
var name : String = ""
var ise_id : Int = 0
var unreach : Bool = false
var sticky_unreach : Bool = false
var config_pending : Bool = false
override internal func propertyMapping() -> [(String?, String?)] {
return [("name", "_name"), ("ise_id", "_ise_id"), ("unreach", "_unreach"), ("sticky_unreach", "_sticky_unreach"), ("config_pending", "_config_pending")]
}
}
You don't have to inherit. You can extend them. Example:
class User : NSManagedObject{
#NSManaged .....
}
//Extension
import EVReflection
extension User : EVReflectable { }
https://github.com/evermeer/EVReflection#extending-existing-objects
Note I'm not aware of EVReflection but I think this answer can generally apply.
Don't use multiple inheritance. Have two separate classes and a mechanism for creating/loading/updating one object from the other. Protocols may allow it to be done in a way that minimises translation boilerplate (possibly using valueForKey(_:) and setValue(_:forKey) if you can know the key names in a safe manner.
It may not even be even be necessary to have an NSManagedObject subclass but just have an instance of NSManagedObject in all your classes that is loaded/created/saved as necessary.
It depends on what functionality you want to use from EVReflection. Since NSManagedObject also has NSObject as it's base class you could use most functions by just setting NSManagedObject as your base class instead of EVObject.
The only thing you have to do is instead of calling EVObject functions directly, you have to implement the code snippets that are in that EVObject method. Almost any function there is just a convenience method that will call the corresponding EVReflection function.
If you have any questions in the future, then please also report this as an issue on GitHub.
Related
I am developing my iOs App and I am using Realm database. As I am totally new to ios developing (also swift and xcode) I have question about structuring data (I've already read some general project structure guidelines but couldn't find the answer). My thinking is connected with Java structures
For Realm databases (RealmSiwft) I created a model like this:
#objcMembers class Patient: Object {
dynamic var patientId:Int = 0
dynamic var refNumber:String = ""
convenience init(id:Int, refNumber:String){
self.init()
self.patinetID = id
self.refNumber = refNumber
}
}
Now, it looks just like a POJO class in Java. But as I learned, this model structure is made that way so it can be able to use Realm.
So the question is, if I need somewhere else in my project to use Patient objects, is this Realm-POJO-model good to use? I mean, should I use it just like a normal Model even when I dont need to make database operations on it? Or should I make this Realm model alike DAO class for databases operations and make another model class like Patient.swift for whenever I want to play with Patient without using databases (I hope not, cause it's so much code duplicating)
And what if I need variables in that Patient Model that won't be stored in database? Can I make it without dynamic? What about init than? That blows my mind, as far as I learn swift it seems so ugly and unstructured, or I just can't switch to it yet...
if I need somewhere else in my project to use Patient objects, is this
Realm-POJO-model good to use?
even when I dont need to make database operations on it?
You can use your Patient object without savings to the DB, move them to different controllers and so on.
what if I need variables in that Patient Model that won't be stored
in database?
Look to ignoredProperties() method.
Can I make it without dynamic?
No you can't because of Realm based on Objective-C object, so this is necessary type.
What about init than?
You can create different Constructors methods, look to the Initialization doc. In case with Realm you should setup values to noticed variables (if you don't give them Default Property Values)
Your class should look like this:
class Patient: Object {
// MARK: - Properties
#objc dynamic var patientId: Int = 0
#objc dynamic var refNumber: String = ""
// MARK: - Meta
// to set the model’s primary key
override class func primaryKey() -> String? {
return "patientId"
}
//Ignoring properties
override static func ignoredProperties() -> [String] {
return ["tmpID"]
}
//It's ok
convenience init(id:Int, refNumber:String){
self.init()
self.patientId = id
self.refNumber = refNumber
}
}
All other detail information you can find in: realm docs
Also you can extend you base code with swift extension:
extension Patient {
var info: String {
return "\(patientId) " + refNumber
}
func isAvailableRefNumber() -> Bool {
return refNumber.length > 6
}
}
I learn the Swift Language and i need to create a manager like a Parse sdk.
For exemple when you initialize your Parse in app you write
Parse.setApplication("...", applicationId:"...")
And later you can write code like this
Parse.doSomething()
The method doSomething() use initial context.
Can you show me in my class should look like? I try some singleton exemple, but a have MyClass.sharedAttribute.doSomething() in case
What you have shown is no indication of singletons whatsoever, it sounds and looks more like a static class with static members and properties:
class MyStatic {
static var appIdA : String?
class func setApplicationId(a : String) {
appIdA = a
}
class func doSomething() {
print(appIdA)
}
}
MyStatic.setApplicationId("blabla")
MyStatic.doSomething() // prints Optional("blabla")
Of course there is the possibility that internally the class is a singleton, but Parse does not seem to be one, just looking at the functions it exposes.
The code comments even state
/*!
The `Parse` class contains static functions that handle global configuration
for the Parse framework.
*/
I have a class called Attendee that inherits from PFObject. Below is its basic definition.
class Attendee: PFObject, PFSubclassing {
override class func initialize() {
var onceToken : dispatch_once_t = 0;
dispatch_once(&onceToken) {
self.registerSubclass()
}
}
class func parseClassName() -> String! {
return "Attendee"
}
}
I want to create a subclass of this object called Speaker such that Speaker inherits from Attendee, which in turn inherits from PFObject.
My question is, will I have to implement the same initialize() and parseClassName() functions for Speaker?
To Parse, Attendee and Speaker are two different class without inheritance. Maybe you should do something like:
You should implement initialize() and parseClassName() for every classes.
Your classes in code should duplicate the classes on the server to avoid confusion both for you and for the Parse SDK code. Any functionality you want to share between the classes should be moved out into another class that you can instantiate / run as required.
The only way it could reasonably work is if your subclass only contained methods, no data. But even then, Parse would either not return the correct class to you, or it would return it at different times than you might expect.
You can absolutely do this on the client-side. If you are trying to store them separately, just return a different value in parseClassName() on each object.
This is my inheritance structure
Protocols
protocol BaseProtocol {
}
protocol ChildProtocol: BaseProtocol {
}
Classes
class BaseClass: NSObject {
var myVar: BaseProtocol!
}
class ChildClass: BaseClass {
override var myVar: ChildProtocol!
}
I'm receiving a compiler error:
Property 'myVar' with type 'ChildProtocol!' cannot override a property with type 'BaseProtocol!'
What is the best approach to achieve this?
UPDATE
I updated the question trying to implement the solution with generics but it does not work :( This is my code (now the real one, without examples)
Protocols
protocol TPLPileInteractorOutput {
}
protocol TPLAddInteractorOutput: TPLPileInteractorOutput {
func errorReceived(error: String)
}
Classes
class TPLPileInteractor<T: TPLPileInteractorOutput>: NSObject, TPLPileInteractorInput {
var output: T!
}
And my children
class TPLAddInteractor<T: TPLAddInteractorOutput>: TPLPileInteractor<TPLPileInteractorOutput>, TPLAddInteractorInput {
}
Well, inside my TPLAddInteractor I can't access self.output, it throws a compiler error, for example
'TPLPileInteractorOutput' does not have a member named 'errorReceived'
Besides that, when I create the instance of TPLAddInteractor
let addInteractor: TPLAddInteractor<TPLAddInteractorOutput> = TPLAddInteractor()
I receive this other error
Generic parameter 'T' cannot be bound to non-#objc protocol type 'TPLAddInteractorOutput'
Any thoughts?
#tskulbru is correct: it can't be done, and this has nothing to do with your protocols. Consider the example below, which also fails…this time with Cannot override with a stored property 'myVar':
class Foo {
}
class Goo: Foo {
}
class BaseClass: NSObject {
var myVar: Foo!
}
class ChildClass: BaseClass {
override var myVar: Foo!
}
To understand why, let's reexamine the docs:
Overriding Properties
You can override an inherited instance or class property to provide
your own custom getter and setter for that property, or to add
property observers to enable the overriding property to observe when
the underlying property value changes.
The implication is that if you are going to override a property, you must write your own getter/setter, or else you must add property observers. Simply replacing one variable type with another is not allowed.
Now for some rampant speculation: why is this the case? Well, consider on the one hand that Swift is intended to be optimized for speed. Having to do runtime type checks in order to determine whether your var is in fact a Foo or a Bar slows things down. Then consider that the language designers likely have a preference for composition over inheritance. If both of these are true, it's not surprising that you cannot override a property's type.
All that said, if you needed to get an equivalent behavior, #tskulbru's solution looks quite elegant, assuming you can get it to compile. :)
I don't think you can do that with protocols
The way i would solve the problem you are having is with the use of generics. This means that you essentially have the classes like this (Updated to a working example).
Protocols
protocol BaseProtocol {
func didSomething()
}
protocol ChildProtocol: BaseProtocol {
func didSomethingElse()
}
Classes
class BaseClass<T: BaseProtocol> {
var myProtocol: T?
func doCallBack() {
myProtocol?.didSomething()
}
}
class ChildClass<T: ChildProtocol> : BaseClass<T> {
override func doCallBack() {
super.doCallBack()
myProtocol?.didSomethingElse()
}
}
Implementation/Example use
class DoesSomethingClass : ChildProtocol {
func doSomething() {
var s = ChildClass<DoesSomethingClass>()
s.myProtocol = self
s.doCallBack()
}
func didSomething() {
println("doSomething()")
}
func didSomethingElse() {
println("doSomethingElse()")
}
}
let foo = DoesSomethingClass()
foo.doSomething()
Remember, you need a class which actually implements the protocol, and its THAT class you actually define as the generic type to the BaseClass/ChildClass. Since the code expects the type to be a type which conforms to the protocol.
There are two ways you can go with your code, depending what you want to achieve with your code (you didn't tell us).
The simple case: you just want to be able to assign an object that confirms to ChildProtocol to myVar.
Solution: don't override myVar. Just use it in ChildClass. You can do this by design of the language Swift. It is one of the basics of object oriented languages.
Second case: you not only want to enable assigning instances of ChildProtocol, you also want to disable to be able to assign instances of BaseProtocol.
If you want to do this, use the Generics solution, provided here in the answers section.
If you are unsure, the simple case is correct for you.
Gerd
As simply using the sharedApplication() method is unavailable in WatchKit, utilizing the AppDelegate as a way to store data for all my interfaces/views is no longer an option in WatchKit. Is there an alternative method to do this in swift for WatchKit apps? I have tried making a singleton class like so:
import Foundation
import UIKit
class data: NSObject {
class var sharedInstance : data {
struct Example {
static let instance = data()
}
return Example.instance
}
var value:Int = 0
var increment:Int = 1
}
(This code is from another StackOverflow post, I just forgot the link.) I then try and access the Integer "value" by calling data.value in an interface controller but I get the error 'data.Type' does not have a member named 'value'. How can I fix this error? Or is there a better way to do what I am trying to achieve?
Thanks
The code data.value attempts to access a class variable or method on the class data called value. Since no such variable or method exists you get the error message.
In your definition value is defined as a property on the class data, so to use it you need a valid instance of data. Your sharedInstance method provides the instance.
Also, the convention in Swift is to capitalize class names, so I recommend using Data.