Assigning an Array value by index does not notify subscribers. about binding HOT 11 CLOSED

This is one of the top google results for Aurelia not reacting to array element changes. In my view, it's no big deal if Aurelia doesn't support this implicitly, but it'd be great to mention a precise recipe to work the issue around and force the update manually. For example, I have found the suggestion to replace this.samples_loaded[i] = true; with this.samples_loaded.splice(i, 1, true); but that doesn't help...

from binding.

@GBreeze aurelia does not observe array mutation via indexed assignment (eg arr[x] = y) because it would require dirty-checking now that Object.observe is discontinued. Use splice instead:

if (!Array.prototype.swap) {
    Array.prototype.swap = function (newIndex: number, oldIndex: number) {
        const temp = this[newIndex];
        this.splice(newIndex, 1, this[oldIndex]);
        this.splice(oldIndex, 1, temp);
        return this;
    }
}

from binding.

What about employing dirty checking in these scenarios? Is there any way to
communicate to the developer at runtime that he shouldn't expect it to
work?
On Apr 7, 2015 10:27 PM, "Rob Eisenberg" [email protected] wrote:

We can't fix this. It's impossible with native Array.observe. It's the one
flaw in the binding system. The only way to get around it is to create a
helper method on array that would notify the changes and use that instead
of the indexer when you want to change something. You can always use splice
as well. But, JS provides no way to override the indexer (at least no way
that isn't insane and non-scalable).

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Reply to this email directly or view it on GitHub
#64 (comment).

from binding.

Anyone having issues with this; check out this example: https://gist.run/?id=c3d618546a0fef10a266109465eed94c

by using splice and the property indexer (string) you can get the binding working - but I believe this is dirty checked.

from binding.

We can't fix this. It's impossible with native Array.observe. It's the one flaw in the binding system. The only way to get around it is to create a helper method on array that would notify the changes and use that instead of the indexer when you want to change something. You can always use splice as well. But, JS provides no way to override the indexer (at least no way that isn't insane and non-scalable).

from binding.

Basically, use dirty checking on array indexes...hmmm. That could work.

On Tue, Apr 7, 2015 at 11:18 PM, Matthew James Davis <
[email protected]> wrote:

What about employing dirty checking in these scenarios? Is there any way to
communicate to the developer at runtime that he shouldn't expect it to
work?
On Apr 7, 2015 10:27 PM, "Rob Eisenberg" [email protected] wrote:

We can't fix this. It's impossible with native Array.observe. It's the
one
flaw in the binding system. The only way to get around it is to create a
helper method on array that would notify the changes and use that instead
of the indexer when you want to change something. You can always use
splice
as well. But, JS provides no way to override the indexer (at least no way
that isn't insane and non-scalable).

—
Reply to this email directly or view it on GitHub
#64 (comment).

—
Reply to this email directly or view it on GitHub
#64 (comment).

Rob Eisenberg,
President - Blue Spire
www.durandaljs.com

from binding.

Not sure if we should do anything about this or not just yet.

from binding.

Does #76 covers an expression like data[0].property ?
It seems my binding doesn't get notified when property changes, even if it is defined as an ES property..

Forgot to mention that I have used Typescript inheritance in my view model, and that the data array is defined on the base class and not on the viewmodel that is used by the view. It can be an issue?

from binding.

@jdanyow Since you are working on the binding docs currently, can you be sure to include this information and recommendation in that. (Along with any other common scenarios you've seen over the last months.)

from binding.

taking suggestions on how/when to warn about this issue: https://github.com/MeirionHughes/aurelia-template-lint/issues/82#issuecomment-250273617

from binding.

What is with polyfills, is there a workaround?

Example:

if (!Array.prototype.swap) {
    Array.prototype.swap = function (newIndex: number, oldIndex: number) {
        let temp = this[newIndex];
        this[newIndex] = this[oldIndex];
        this[oldIndex] = temp;
        return this
    }
}

this does not reflect on a 'repeat.for' binding :-|

from binding.