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Comment by noncoml | Hacker News Reader

> Some common rules of thumb for determining what kind of data should be put into Redux:

> > - Do other parts of the application care about this data? > - Do you need to be able to create further derived data based on this original data? > - Is the same data being used to drive multiple components? > - Is there value to you in being able to restore this state to a given point in time (ie, time travel debugging)? > - Do you want to cache the data (ie, use what's in state if it's already there instead of re-requesting it)?

Won't having half your state outside the store and the other half inside add unneeded complexity and make your code even more difficult to read?

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The most common (and to me, reasonable) situation would be to keep all fetched data in Redux, any other app state that needs to be referenced by multiple components, and possibly some bits of UI state as needed (like "currently showing a modal for editing an item"). Component state would be primarily used for "is this dropdown open"-type values.

But, as I said, it's totally up to you to decide what lives where :)

Another way to look at it: What data is OK to lose if you refresh the page? That to me is component state. You don't have a url: '.../?dropdown.001=open' / '.../?dropdown.001=closed' so that's likely purely component state (not application state).

Very good point. Ditto with hot reloading components. React-Hot-Loader tries to retain component state via complex use of code transformation and "proxy" components, but it's very finicky and has lots of edge cases. Using the "plain" HMR API to just swap out the entire component tree on any component change is much simpler and more reliable, but doesn't preserve component state. Choosing to keep something in Redux so that it gets retained during that situation is a valid choice.

Yes.

And it usually isn't anything as sane as half in the store and half in one other place.

It's like 70% in the store, and 5% in component#1, and 8% in component#2, and 16% in component#3 (duplicating some stuff from component#1 and sorta duplicating some stuff from component#2 with some notes that someone should refactor all this and move those to redux) and the rest of it is only god knows where.

And then there is some hard to track down UI bug because using setState() turns out to be really much slower than you think it is going to be.

But Redux is so boilerplatey and heavy handed that it made sense in each individual case to the original coder/reviewer to not use it.

It really depends on what you do. If you use component state in high-level components and pass it around a lot, yes it will likely lead to hard to understand code. But I see no issue with using state for state internal to low-level components, like an input field's value or whether a paragraph with a 'read more' button is expanded.

Of course, once you need to access a piece of state from outside that component you should probably move it to the store. But until then you are just creating unnecessary complexity by cluttering global state.

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