Missing didUpdate for componentDidUpdate lifecycle function

[chimon2000]

Attempting to call a state handler using onChange results in an infinite loop. It would be nice if there was a didUpdate function that mirrored the capabilities of (p)react's componentDidUpdate, that allows you to immediately call setState given some conditional.

This feature is important when utilizing routing or similar functionality where a change in props would cause a reset / refetch of data.

As a workaround, calling the state handler in a setTimeout worked fine.

[fahad19]

@chimon2000: Thanks for the issue, Ryan!

onChange is meant for only returning new props (either sync or async), without having any other side-effects.

I will have to dig deeper into how componentDidUpdate can possible work from proppy package.

Could you please share example snippets how you wish to use it? Thanks!

[chimon2000]

Sure, I could see the signature being the similar to onChange

didUpdate(propName, (prop, providers) => void)

didUpdate( (prevProps, nextProps) => true, (props, providers) => void)

Consider the following rudimentary example, where based off of a route change, I want to reset my state.

	...
	//State handler to reset count
    withStateHandlers(
        { count: 10 },
        {
            reset: () => () => ({ count: 0 })
        }
    ),
	//Shorthand syntax.
    didUpdate('user', props => {
        props.reset()
    }),
	//Same thing but with longhand syntax for developer's control.
    didUpdate((prevProps, newProps) => prevProps.user !== newProps.user, props => props.reset(),
	...

Perhaps didUpdate is not the right name for the function, since we really want to execute some handler based the component updating and some additional condition.

[fahad19]

That is a valid use case indeed. I’ll have to think how something like that can be done without risking infinite loop.

If you wanna take a dig at it and start a branch, that would help a lot. I can jump in with the already established test cases then.