Why does MobX 5 array still have the index violation issue?

[vilicvane]

I have a:

1. Question: Feel free to just state your question. For a quick answer, there are usually people online at our Gitter channel
2. Issue

[mobx.array] Index out of bounds, 1 is larger than 0

https://runkit.com/embed/56jty1h3u27y

[mweststrate]

There are a few reasons

1. Nobody took the effort to remove it :)
2. This keeps feature parity between MobX 4 and 5, so that it is easier to migrate from 5 back to 4, if your browser support for example demands it
3. Imho out-of-bound assignments that result in sparse arrays are a bad practice anyway :).

[vilicvane]

@mweststrate The 2nd reason doesn't look valid to me, because of the 3rd one (as most of the time we don't write out-of-bound assignment). 😂

I am encountering this because of a third-party library https://github.com/flitbit/diff:

elements in arrays are now processed in reverse order, which fixes a few nagging bugs but may break some users

Will happy to send a PR for this if you like.

[mweststrate]

weird, why would a diff need out of bound assignments? Is .slice() your array first a simple work around? Op vr 30 nov. 2018 om 15:20 schreef vilicvane <notifications@github.com>:

…

@mweststrate <https://github.com/mweststrate> The 2nd reason doesn't look valid to me, because of the 3rd one (as most of the time we don't write out-of-bound assignment). 😂 I am encountering this because of a third-party library https://github.com/flitbit/diff: elements in arrays are now processed in reverse order, which fixes a few nagging bugs but may break some users Will happy to send a PR for this if you like. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1822 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABvGhNxrNL9hLycFH6DdDFfXrXePyTCYks5u0T6YgaJpZM4YwC0M> .

[vilicvane]

@mweststrate It's happening on applying changes to existing object. Related issue flitbit/diff#47

I don't see why slice would solve this issue, but fortunately there is an alternative to this functionality in my inventory that works with MobX.

[mweststrate]

With .slice you could get a temporarily copy of the observable array, that doesn't have any mobx specific behavior. That could be basis for diff, or target for the changes. After that you could do observableArray.replace(modifiedArray) to apply the changes back in a single action to MobX. Op vr 30 nov. 2018 om 16:32 schreef vilicvane <notifications@github.com>:

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@mweststrate <https://github.com/mweststrate> It's happening on applying changes to existing object. Related issue flitbit/diff#47 <flitbit/diff#47> I don't see why slice would solve this issue, but fortunately there is an alternative to this functionality in my inventory that works with MobX. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1822 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABvGhMANfnn_-BqLuuH9BZp46PXfZUJnks5u0U-LgaJpZM4YwC0M> .

[vilicvane]

@mweststrate Ahh, unfortunately not a simple workaround in my case. The object structure is unpredictable (it's like updating/restoring custom objects between versions). Thanks though.

[lock]

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