Ionic ion-nav-title badge value not updated when filtering

ionic-v1
1

I’m new with ionic framework, i have problem updating my badge dynamic value, see my code below,

<ion-view>
<ion-nav-title>
    <div class="item" style="padding: 0; background: transparent;">
        <span>My Title Here</span>
        <span class="badge badge-assertive">
            {{ MyRecordAgain.length }} PCS
        </span>
    </div>
</ion-nav-title>

<ion-content>
<ion-list>
    <ion-item collection-repeat="rec in MyRecordAgain = (MyRecord | searchContacts:filterKey | orderBy:'NAME')">
            {{rec.NAME}}
        </ion-item>
    </ion-list>
</ion-content>

this code always show “PCS” on badge title. the right value is “XXX PCS”, where XXX is my record count when filtering.

but when i change my code with this code, the value is right.

<ion-nav-title>
    <div class="item" style="padding: 0; background: transparent;">
        <span>My Title Here</span>
        <span class="badge badge-assertive">
            {{ (MyRecord | searchContacts:filterKey | orderBy:'NAME').length }} PCS
        </span>
    </div>
</ion-nav-title>

is it bug? i use ionic v1.1.0