Update _nodeIndex when child changes

thomasboyt / react

React is a JavaScript library for building user interfaces. It's declarative, efficient, and extremely flexible. What's more, it works with the libraries and frameworks that you already know.

http://facebook.github.io/react/

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Update _nodeIndex when child changes #7

Open thomasboyt opened 9 years ago

thomasboyt commented 9 years ago

This is pretty difficult & important.

When the following structure changes from:

<Main>
  <Composite : frag>
    <one />
    <two />
  </Composite>
  <Composite : frag>
    <one />
    <two />
  </Composite>
</Main>

to:

<Main>
  <Composite : frag>
    <one />
  </Composite>
  <Composite : frag>
    <one />
    <two />
  </Composite>
</Main>

the only update cycle that gets called is for the first composite, and the second one doesn't know that a previous sibling fragment was updated, so its _nodeIndex is now off by one.

thomasboyt commented 9 years ago

wonder if there's a way to trigger some index-updating cycle on Main, given that a child fragment changed...

thomasboyt commented 9 years ago

this is, if nothing else, a predicted problem: https://github.com/facebook/react/issues/2127#issuecomment-108067345

[referencing nodes by mountIndex] does not work when one "node" can suddenly become any number of nodes and this may happen without invoking the parent and it may also happen several components deep (wrapping)

thomasboyt commented 9 years ago

options:

when a composite component's update cycle is hit, if its nodeCount changes, trigger some way to increase the nodeIndexes of subsequent siblings
- concerned that there's not going to be a simple, and almost certainly not an efficient, way to look up siblings
~~trigger the parent update cycle when a fragment changes~~
- horrible performance indications, adds user-facing special-case behavior to fragments that we should be trying to avoid, this is a garbage option
call some method on the parent that only updates nodeIndexes
- basically equivalent to the first option
- parent.updateNodeIndexes(thisIndex, newNodeCount)
- how do we look up the parent in a performant way?
- can the parent access the children after some nodeIndex in a performant manner? sounds like an expensive filter

thomasboyt commented 9 years ago

The frustrating thing about accessing the parent is that there doesn't seem to be a good way to do it, at all.

I'm imagining a CompositeComponent storing a reference to its parent, somehow, but I don't know if the parent could change out from under it after initial mount. Looking up by root ID seems to be (a) impossible and (b) a super-gross hack even if it was.