Ionic-framework: VirtualScroll does not work with Immutable.List
Short description of the problem:
Trying to replace *ngFor="let item of items" with virtualScroll alternative does not render any item (nothing added in the dom) or each virtualItem is empty if items is an Immutable.List. Immutable.List is enumerable and thus works fine with ngFor and since angular2 and immutability work so well together I believe this should work.
What behavior are you expecting?
Render items of an immutable list correctly
Which Ionic Version? 1.x or 2.x
Ionic 2 Beta 11
Plunker that shows an example of your issue
http://plnkr.co/edit/2c5ZIyDyGb12kwtQ4jXW?p=preview
Run ionic info from terminal/cmd prompt: (paste output below)
Cordova CLI: 6.3.0
Gulp version: CLI version 3.9.1
Gulp local: Local version 3.9.1
Ionic Framework Version: 2.0.0-beta.11
Ionic CLI Version: 2.0.0-beta.36
Ionic App Lib Version: 2.0.0-beta.19
ios-deploy version: 1.8.6
ios-sim version: 5.0.6
OS: Mac OS X El Capitan
Node Version: v4.3.1
Xcode version: Xcode 7.3.1 Build version 7D1014
masimplo
All 3 comments
To add to this issue, after RC0 that angular final was used, providing an array of immutable objects into VirtualScroll leads to severe performance degradation as VirtualScroll does its own change detection triggering which leads to a deep comparison (through devModeEqual) of the immutable objects that is just taking crazy amounts of time.
I believe VirtualScroll should be compatible with the OnPush change detection strategy in order to support immutable objects.
UPDATE 20/04/17:
I believe that this is no longer the case, as item comparisons are using Angular4.0 diff comparisons that account for immutable items, but List enumerations issues inside Virtual Scroll still remain unchanged.
masimplo
on 10 Nov 2016
This is still an issue on latest Ionic (v3.0.1) and here is an updated plunker demonstrating the issue once more.
http://plnkr.co/edit/2Pz0fIX9MV7er12UaFRf?p=preview
Our app uses immutable sets and lists everywhere, but due to the fact that we have to display 1000s of records in a scrollable list, we have to use virtual scroll. This requires that all data is converted back to mutable objects (very costly) and all the components used inside the virtual scroll have to accept mutable objects as well.
This way we are sort of trapped as we have to use virtual scroll for better performance, but we are degrading performance due to trying to be compatible with virtual scroll.
masimplo
on 18 Apr 2017
Thanks for the issue! This issue is being closed due to inactivity. If this is still an issue with the latest version of Ionic, please create a new issue and ensure the template is fully filled out.
Thank you for using Ionic!
![ionitron-bot[bot] picture](https://avatars1.githubusercontent.com/in/8640?v=4&s=40)
ionitron-bot[bot]
on 20 Apr 2018
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Most helpful comment
To add to this issue, after RC0 that angular final was used, providing an array of immutable objects into VirtualScroll leads to severe performance degradation as VirtualScroll does its own change detection triggering which leads to a deep comparison (through devModeEqual) of the immutable objects that is just taking crazy amounts of time.
I believe VirtualScroll should be compatible with the OnPush change detection strategy in order to support immutable objects.
UPDATE 20/04/17:
I believe that this is no longer the case, as item comparisons are using Angular4.0 diff comparisons that account for immutable items, but List enumerations issues inside Virtual Scroll still remain unchanged.