ng-blur失去焦点执行事件

<label class="item item-input item-stacked-label">
                <span class="input-label">UPC</span>
                <input type="text" ng-model="vm.product.upc" readonly="readonly">
            </label>
            <label class="item item-input item-stacked-label">
                <span class="input-label">PLU</span>
                <input type="text" ng-model="vm.product.plu" ng-blur="vm.checkPLU()">
            </label>