I have a problem with Typhoon dependency injection framework.
My viewcontroller MainViewController depends on dataProvider property that I want to declare as AnyObject corresponding to protocol DataProviderProtocol
class MainViewController: UIViewController {
// Compiler error here
var dataProvider : DataProviderProtocol!
// something more
}
protocol DataProviderProtocol {
func fetchAllBanks(closure : ([BankObject]) -> Void)
}
class TestDataProvider: NSObject, CEDataProviderProtocol {
func fetchAllBanks(closure : ([CEBankObject]) -> Void) {
var resultBanks = ///////code that creates test data
closure(resultBanks);
}
I want this dataProvider property to be injected by the Typhoon and initialized to the corresponding instance of class TestDataProvider, that implements this protocol. But I also have RealDataProvider that also corresponds to the DataProviderProtocol and might be used sometimes
But this code crashes with the message
Can't inject property 'dataProvider' for object
''. Setter selector not
found. Make sure that property exists and writable'
I can inject this property without crashes if I use the property class of TestDataProvider, but this disables the ability to inject different DataProviderProtocol implementations.
I understand this this crash happens because DataProviderProtocol property type is not NSObject successor. But I just can't find a way to declare property as NSObject<DataProviderProtocol> in Swift
I would appreciate any help
P.S. My Assembly class
public class CEAppAssembly:TyphoonAssembly {
//uiviewcontrollers' components assembly
var mainComponentsAssembly : CEMainComponentsAssembly!
/**
UI Dependencies
**/
public dynamic func mainViewController() -> AnyObject {
return TyphoonDefinition.withClass(MainViewController.self) {
(definition) in
definition.injectProperty("dataProvider", with: self.mainComponentsAssembly.dataProvider())
}
}
Typhoon uses the Objective-C run-time introspection and dynamic features. Therefore:
Protocols must be marked with the '#objc' directive.
Types incompatible with Objective-C (ie 'pure swift') can't be injected.
There's more information about this in the Quick Start guide. If you're still having trouble after reviewing and making those changes, let us know.
We plan to release a Pure Swift version of Typhoon in the near future.
Related
The situation is following: I'm using a protocol to inject dependencies and the best way I found to implement this in Swift is to use the associatedtype keyword. I am also using protocol composition since some implementations of TestProtocol need more than one dependency.
protocol TestProtocol: class {
associatedtype Dependencies
func inject(_ dependency: Dependencies)
}
protocol HasSomething {
var something: Something { get set }
}
protocol HasSomethingElse {
var somethingElse: SomethingElse { get set }
}
To use this I found that I'll need to use generics like this:
class TestService<T> where T: TestProtocol, T.Dependencies == TestService {
weak var testProtocol: T?
init(with testProtocol: T) {
self.testProtocol = testProtocol
self.testProtocol?.inject(self)
}
}
Now when I want to use this service somewhere else and I'm trying to initiate it I get following problem:
The parameter is displayed as _ and not as the protocol name TestProtocol.
Let's say I would use this code in a library. How would a user know (without reading the documentation of course) what type could be used in this context when he is not even knowing what protocol he has to implement?
Is there a better way on how to use dependency injection with the type actually being displayed to the user, or am I doing something wrong in the where clause of the TestService class, or is this simply not possible in the current versions of Swift?
There is nothing wrong with your code, this is simply not possible.
class TestService<T> where T: TestProtocol
The where clause means T could be anything, with the constraint that the given object must conform to TestProtocol.
The Xcode autocomplete feature only displays the resolved type when available, but it doesn't show the constraints on a generic, and unfortunately there is nothing you can do about that.
You have the exact same issue in the swift standard library, with Dictionary for example
public struct Dictionary<Key, Value> where Key : Hashable {
public init(dictionaryLiteral elements: (Key, Value)...) {
// ..
}
}
The generic Key as a constraint to Hashable, but Xcode still shows _ in the autocomplete list.
I guess Swift developers are use to this behaviour, so it won't be a big issue, even if your code is embedded in a library.
How would a user know (without reading the documentation of course) what type could be used in this context when he is not even knowing what protocol he has to implement?
Because Xcode is pretty clear about the protocol requirement.
If I try to initialize the TestService with a String I'll get the error:
Referencing initializer 'init(with:)' on 'TestService' requires that 'String' conform to 'TestProtocol'
Which is pretty self explanatory.
Actually at the time of init(with testProtocol: T) Compiler doesn't know about T of course because it is generic
if you provide directly class it will show you in suggestion
For example
class TestService<T:Something> {
weak var testProtocol: T?
init(with testProtocol: T) {
self.testProtocol = testProtocol
}
}
Now you will see compiler know that it need SomeThing at T
For your case For TestProtocol You can replace with with something user readable world. for next time compiler will give you provided type as suggestion
For Example
class TestService<T:TestProtocol> {
weak var testProtocol: T?
init(with testProtocol: T) {
self.testProtocol = testProtocol
}
func add(t:T) {
}
}
class Test {
init() {
let t = Something()
let ts = TestService(with: t)
}
}
In Test class you can type ts.add now it knows
I can't use private property in extension. My extension is in another file.
How can I use private property in extension?
Update
Starting with Swift 4, extensions can access the private properties of a type declared in the same file. See Access Levels.
If a property is declared private, its access is restricted to the enclosing declaration, and to extensions of that declaration that are in the same file.
If the property is declared fileprivate, it can only be used within the file it is declared (and by anything in that file).
If the property is declared internal (the default), it can only be used within the module it is declared (and by anything in that file).
If the property is declared public or open, it can be used by anything within the module as well as outside of the module by files that import the module it is declared in.
While #nhgrif is correct about how painful is that protected is missing in Swift, There is a way around.
Wrap your object with protocol, and declare only about the methods and properties that you wish to expose.
For Example
MyUtiltyClass.swift
protocol IMyUtiltyClass {
func doSomething()
}
class MyUtiltyClass : IMyUtiltyClass {
static let shared : IMyUtiltyClass = MyUtiltyClass()
/*private*/
func doSomethingPrivately() {
}
}
MyUtiltyClass+DoSomething.swift
extension MyUtiltyClass {
func doSomething() {
self.doSomethingPrivately()
print("doing something")
}
}
And then you treat the object as the interface type and not the class/struct type directly.
MyViewController.swift
class MyViewController : UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
MyUtiltyClass.shared.doSomething()
/*
//⚠️ compiler error
MyUtiltyClass.shared.doSomethingPrivately()
*/
}
}
Happy Coding 👨💻
It's not a good practice to write a private variable in extensions (even if we can). It will introduce unexpected bugs.
If you want to access the variable, you can use private(set) for that variable to make it read only for outside world.
Ex.
private(set) var myPrivateVariable:Int
I have class:
class InformationTableViewController: UITableViewController {
private var cos: Int!
}
And I'm trying to inject property:
public dynamic func informationTableViewController() -> AnyObject {
return TyphoonDefinition.withClass(InformationTableViewController.self) {
(definition) in
definition.injectProperty("cos", with: 3)
}
}
When it's a simple class it works normal. But when I use InformationTableViewController on Storyboard (as some view class) I'm getting error:
'Can't inject property 'cos' for object 'Blah.InformationTableViewController: 0x7fca3300afe0'. Setter selector not found. Make sure that property exists and writable'
What's the problem?
Private access modifier restricts the use of an entity to its own defining source file.
So one problem is that you are trying to set your property from outside of it private scope. Remove private keyword from property declaration.
Another problem here is that you are trying to inject primitive type.
In Obj-C Typhoon has support of injecting primitive types but not in Swift yet.
Every class you want to inject has to be a subclass of NSObject in some way (either by subclassing or adding #objc modifier).
As a workaround you may use NSNumber instead of an Int type for your property.
class InformationTableViewController: UITableViewController {
var cos: NSNumber!
}
Assembly:
public dynamic func informationTableViewController() -> AnyObject {
return TyphoonDefinition.withClass(InformationTableViewController.self) {
(definition) in
definition.injectProperty("cos", with: NSNumber.init(int: 3))
}
}
I have created a project to test the Typhoon framework , I have created two classes ApplicationAssembly and CoreAssembly where I inject some properties and constructors and a default Configuration.plist to load data from it.
ApplicationAssembly
public class ApplicationAssembly: TyphoonAssembly {
public dynamic func config() -> AnyObject {
return TyphoonDefinition.configDefinitionWithName("Config.plist")
}
}
CoreAssembly
public class CoreAssembly: TyphoonAssembly {
public dynamic func apiHandler() -> AnyObject {
return TyphoonDefinition.withClass(ApiHandler.self) {
(definition) in
definition.useInitializer("initWithDebugging:debugProcess:mainURL:") {
(initializer) in
initializer.injectParameterWith(TyphoonConfig("debug_mode"))
initializer.injectParameterWith(TyphoonConfig("debug_path"))
initializer.injectParameterWith(TyphoonConfig("api_url"))
}
definition.scope = TyphoonScope.Singleton
}
}
public dynamic func viewController() -> AnyObject {
return TyphoonDefinition.withClass(ViewController.self) {
(definition) in
definition.injectProperty("apiHandler", with:self.apiHandler())
}
}
}
I set in my Info.plist the TyphoonInitialAssemblies first the ApplicationAssembly and then the CoreAssembly.
Everything works fine without exceptions or anything except that the app never enters in AppDelegate neither in the ViewController class. I don't know maybe I missed something in the doc or anything.
What I'm missing here?
Why in debug not enter in the ViewController class that is the initial view controller in Storyboard?
The problem was that the ApiHandler class does not extend NSObject, which is a requirement. This is because Typhoon is an introspective Dependency Injection container. As Swift has no native introspection it uses the Objective-C run-time.
The App should not however have crashed in such an obfuscated way. I have opened an issue to look at how to fail with a meaningful error, rather than infinitely recurse.
After solving the initial problem, I also noted that the init method for ApiHandler passing in a Swift Bool object. This needs to be an NSNumber.
init(debugging : NSNumber, debugProcess : String, mainURL : String) {
self.debugging = debugging.boolValue
self.debugProcess = debugProcess
self.mainURL = mainURL
}
Given that Typhoon uses the Objective-C runtime, there are a few quirks to using it with Swift - the same kinds of rules outlined for using Swift with KVO apply.
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