Sinks not working for child workflows

[AlexandruIstrate]

Sinks not working for child workflows

[AlexandruIstrate]

It seems like the PR by @bencochran fixes my problem. I'm happy to close the issue if that's alright with you.
Thanks for the help!

[bencochran]

It looks like your ViewController is missing the addChild(container) and container.didMove(toParent:), resulting in UI events not being correctly delivered to the text field and the text field delegate methods in HelloViewController never being called. Put up a PR that appears to fix the issue on my end.

[zach-klippenstein]

I'm not very familiar with Swift so this is just a guess, but this line looks suspicious to me:

.rendered(with: context, key: UUID().description)

Is that generating a new UUID every time? If so, all your child workflows will be restarted on every render pass, and the ones from the previous render pass will be stopped, which is why their sinks stop working.

[AlexandruIstrate]

You are indeed correct. UUID() generates a new universally unique identifier every time. That might be the problem. If I am correct, the key must be unique between all of the children. So I could use, for example, the name of the workflow, such as TextWorkflow or Child 1, Child 2, etc?
I'll give this a try and let you know if it works.
Thank you for the quick reply!

[zach-klippenstein]

That should work. As long as the key is derived from something that identifies the child workflow consistently across render passes.

[bencochran]

Yeah, you’ll need stable (and unique) keys between renders. I’d consider making some kind of identifier part of the items held in WorkflowData (like maybe var workflows: [(identifier: String, workflow: AnyWorkflow<…>], or a struct to wrap that up).

One other thing you’re going to need is to implement screenDidChange in your GraphViewController. When your workflow tree rerenders, the new root screen will be handed to that method to update itself and its children (calling update(screen:environment:) on each child DescribedViewController with its appropriate screen). Which also means you’ll need to keep those child view controllers around for use somewhere (another good use for the stable identifiers defined above).

[AlexandruIstrate]

Also, if I want to render children, should I use child.rendered(with:key:) or context.render(workflow:key:outputMap:)? What is the difference between the two?

[AlexandruIstrate]

I finally figured it out. It turns out the sink wasn't firing because of the way I was presenting my ContainerViewController. Instead of using present(_:animated:completion:), I was hosting the view controller as a child like this:

let container = ContainerViewController(
    workflow: GraphWorkflow(data: WorkflowData(key: "Root"))
)
        
let containerView = container.view!
self.view.addSubview(containerView)
containerView.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([
    containerView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
    containerView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
    containerView.topAnchor.constraint(equalTo: self.view.topAnchor),
    containerView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
])

What I should have used was as simple as:

let container = ContainerViewController(
    workflow: GraphWorkflow(data: WorkflowData(key: "Root"))
)
present(container, animated: true, completion: nil)

Once I swapped out the initial code with the new version, everything started working. However, I would like to have the ContainerViewController embedded in another UIViewController, via an embed segue or just programatically. Is there any way to make that work and still have the sink operational?

[dhavalshreyas]

Is there a sample project where this bug repros? Happy to look into it if there is.

Is the block that's calling sink.send() getting called? Is the Action.apply() getting called?

[AlexandruIstrate]

Is there a sample project where this bug repros? Happy to look into it if there is.

Is the block that's calling sink.send() getting called? Is the Action.apply() getting called?

Currently, I am using Square Workflow in a private project. I'm afraid I can't share the source code of that project. I do, however, have a test/demo project that consists of some simple code that essentially reproduces the bug in question. I can upload the demo project to GitHub if you would like to experiment with it. I would also make sure to mark the problem areas with comments and explanations.

[dhavalshreyas]

Thanks @AlexandruIstrate! That'll be perfect.

[AlexandruIstrate]

I have created a repository with the demo project. Essentially, in the file ViewController.swift you have the choice between two methods (1 and 2). They are marked so that you know what each does. The difference between the two is that in one, the ViewController is getting presented modally over the top and in the other it gets embedded as a child.

Link to the repo: SquareWorkflowDemo