Typhoon loading storyboard programmatically appears to perform asynchronous instantiation without blocking

问题

I am developing an iOS application and am trying to integrate Typhoon into the testing. I am currently trying to mock out a dependency in a view controller that comes from the storyboard, so with in my assembly:

public dynamic var systemComponents: SystemComponents!
public dynamic func storyboard() -> AnyObject {
    return TyphoonDefinition.withClass(TyphoonStoryboard.self) {
        (definition) in
        definition.useInitializer("storyboardWithName:factory:bundle:") {
            (initializer) in
            initializer.injectParameterWith("Main")
            initializer.injectParameterWith(self)
            initializer.injectParameterWith(NSBundle.mainBundle())
        }
    }
}

I want to create a CameraModeViewController (the class I am unit testing) with its dependency upon a system-camera-functions-providing protocol mocked out. The dependency is dynamic var cameraProvider: CameraAPIProvider?. I think I correctly created a replacement collaborating assembly to replace systemComponents; MockSystemComponents is a subclass of SystemComponents that overrides functions. This is where I inject the mock:

let assembly = ApplicationAssembly().activateWithCollaboratingAssemblies([
                            MockSystemComponents(camera: true)
                        ])
let storyboard = assembly.storyboard()
subject = storyboard.instantiateViewControllerWithIdentifier("Camera-Mode") as! CameraModeViewController

The next line of code in the tests is let _ = subject.view, which I learned is a trick to call viewDidLoad and get all the storyboard-linked IBOutlets, one of which is required for this test.

However, I am getting very mysterious result: sometimes but not always, all the tests fail because in the viewDidLoad I make a call to the dependency (cameraProvider), and I get an "unrecognized message sent to class" error. The error seems to indicate that at the time the message is sent (which is a correct instance method in protocol CameraAPIProvider) the field is currently a CLASS and not an instance: it interprets the message as +[MockSystemCamera cameraStreamLayer] as reported in the error message.

~~~BUT~~~

Here's the kicker: if I add a breakpoint between the calls to assembly.storyboard() and subject.view, the tests always pass. Everything is set up correctly, and the message is correctly sent to an instance without this "class method" bogus interpretation. Therefore, I have to wonder if Typhoon does some kind of asynchronous procedure in the injection that I have to wait for? Possibly only when dealing with storyboard-delivered view controllers? And if so, is there any way to make sure it blocks?

After digging around in Typhoon's source for a while, I get the impression that in the TyphoonDefinition(Instance Builder) initializeInstanceWithArgs:factory: method there is an __block id instance that is temporarily a Class type, and then is replaced with an instance of that type; and possibly this can be called asynchronously without blocking, so the injected member is left as a Class type?

UPDATE: Adding the code for MockSystemComponents(camera:). Note that SystemComponents inherits from TyphoonAssembly.

@objc
public class MockSystemComponents: SystemComponents {
    var cameraAvailable: NSNumber

    init(camera: NSNumber) {
        self.cameraAvailable = camera
        super.init()
    }

    public override func systemCameraProvider() -> AnyObject {
        return TyphoonDefinition.withClass(MockSystemCamera.self) {
            (definition) in
            definition.useInitializer("initWithAvailable:") {
                (initializer) in
                initializer.injectParameterWith(self.cameraAvailable)
            }
        }
    }
}

UPDATE #2: I tried replacing the constructor injection in the MockSystemComponents.systemCameraProvider() with a property injection. Different issue, but I suspect it's equivalent in cause: now, the property that is injected (declared optional) is still nil some of the time when I go to unwrap it (but not always -- probably about 4/5 of test runs fail, about the same as before).

UPDATE #3: have tried using the following code block, using factory construction according to this answer (note that setting factory directly didn't work as that OP did, but I think I correctly used the feature added in response to Jasper's issue). The results are the same as when using property injection like Update #2 above), so no dice there.

回答1:

This issue was in fact arising even before the call to the instantiation. In fact, the problem was assemblies aren't generally intended to be stateful. There are a few ways to get around this, but the one I used -- having a member variable and an initializer method -- is NOT recommended. The problem with doing this is that in the activateWithCollaboratingAssemblies method, all the instance methods of the assembly are enumerated for definitions, and initializers will actually get called on the collaborating assembly. Consequently, even if you create your assembly with an initializer, it may get called again with a bogus value.

Note that the reason there appeared to be async behavior is actually that there is nondeterministic order in which definitions are assembled (property of storing them in an NSDictionary). This means that if activateWithCollaboratingAssemblies happens to enumerate methods which depend on state first, they'll work fine; but if the initializer is enumerated first, and the state is destroyed, definitions that are created after will be borked.

来源：https://stackoverflow.com/questions/36166302/typhoon-loading-storyboard-programmatically-appears-to-perform-asynchronous-inst

标签

swift

unit-testing

storyboard

xcode7

typhoon