[ionic2] virtualTrackBy seem to not be working

I was looking for some optimisation in my app then i stumble uppon something weird. In my template i’ve done this:

<ion-content>
    <ion-list [virtualScroll]="storeStands.collection$ | async"
        [virtualTrackBy]="trackStand"
        [headerFn]="alphabetical" >
        <ion-item-divider *virtualHeader="let header">{{ header }}</ion-item-divider>
        <a ion-item text-wrap
            *virtualItem="let stand"
            [navPush]="[standPage, { stand: stand }]">
            <h2>{{ stand.organization }}</h2>
        </a>
    </ion-list>
</ion-content>

In my controller

trackStand(index, stand: Stand) {
    console.log(index, stand);
    return stand.id;
}

Putting a console log in trackStand function but it’s never called (as opposed with ngForTrackBy).

Explorating futher i put a console.log(val) inside the ionic-angular/components/virtual-scroll/virtual-scroll.js:305 to see if my parameter was listened, and i get undefined.

    set: function (val) {
        this._trackBy = val;
    }

Moving back to my template i set [virtualTrackBy]="'trackStand'" and i then get 'trackStand' inside virtual-scroll.js:306.

But was more curious an tracked where this._trackBy was used, in the same file virtual-scroll.js:260 inside a condition.

set: function (val) {
    this._records = val;
    if (util_1.isBlank(this._differ) && util_1.isPresent(val)) {
        this._differ = this._iterableDiffers.find(val).create(this._cd, this._trackBy);
    }
}

I put console.log(this._trackBy, this._differ) inside that condition and surprise, this._trackBy is undefined and this._differ has a method _trackByFn with attribute name: 'trackByIdentity'.

Putting the console.log just before the condition, the this._trackBy display two times, one with undefined and one with 'trackStand', this._differ doesn’t change at all.

A final test was to remove the condition if (util_1.isBlank(this._differ) && util_1.isPresent(val)) and there this._differ._trackByFn.name was empty when [virtualTrackBy]="trackStand" and only there it work as expected.

So my conclusion is, when this._differ is set, and even if val change, this._differ isn’t changed, and doesn’t take in account this._trackBy.

[faraazc]

+1

[jbgomez21]

Any update about this issue? I have the same problem with ionic 2.0.0 RC4, [virtualTrackBy]=“trackStand” does not execute, if (util_1.isBlank(this._differ) && util_1.isPresent(val)) condition it’s alway false.