/**
    * Converts units, updates model
    */
    unitConverter(index: number): Promise<number> {


        const unitElement = this.products[index].units.get(this.products[index].unitId);

        //if unit never loaded
        if (unitElement === undefined || unitElement.basicUnit === undefined) {

            //load unit and change unit data

            this.products[index].unitsLoaded = false;

            const params: b2b.UnitConvertRequest = {
                cartId: this.products[index].cartId.toString() || '1',
                id: this.products[index].id.toString(),
                unitNo: this.products[index].unitId.toString() || '0',
                features: this.parametersToString(0) || '',
                warehouseId: this.filters.currentFilter.warehouse.id || '0'
            };


            return this.unitConverterRequest(params).then(res => {

                const unitData = Object.assign(res, {
                    converter: (res.auxiliaryUnit) ? FormattingUtils.unitConverterString(res.denominator, res.auxiliaryUnit, res.numerator, res.basicUnit) : null,
                    max: FormattingUtils.stringToNum(res.stockLevel)
                });

                this.products[index].units.set(this.products[index].unitId, unitData);

                this.products[index] = Object.assign(this.products[index], unitData);

                this.products[index].unitsLoaded = true;

                return index;
            });

        } else {

            //change unit data

            this.products[index] = Object.assign(this.products[index], unitElement);

            return Promise.resolve(index);
        }


    }