Trouble with text inputs and double update roundtrips

[rupert]

@lazurski

In my app I have a complex type representing a document. There are many possible transformations that can be applied to it. For versioning purposes every time any transformation is applied I need to capture and store the current time. I want my type to be opaque and transformations to be atomic. But to get time I need to perform a Time.now task and get another Msg with time. I can’t think about any other way than having two updates for every input event.

If you are using the timestamp to version documents, in order to ensure that each version is uniquely tagged and ordered, might you be able to achieve the same thing by using a simple counter? That is, instead of getting the timestamp on each document update, just store a current version as an Int in the model and increment it each time?

@albertdahlin

In general I think one should avoid passing the Model in a Msg since this can cause tricky concurrency behaviours that are hard to reason about.

I would second this - I made an Ellie to show what can happen if multiple events fire in quick succession. A later update can overwrite the model with stale data from an earlier state:

https://ellie-app.com/yVC9wPk33xa1