Instruments.prototype.sortInstruments = function (sortParam, desc) {
        var sortInstruments;
        if (!desc) {
            sortInstruments = _.sortBy(this.instruments.value, function (instrument) {
                return instrument[sortParam];
            });
        } else {
            sortInstruments = _.sortBy(this.instruments.value, function (instrument) {
                return instrument[sortParam];
            }).reverse();
        }
        this.instruments.value = sortInstruments;
    };

    Instruments.prototype.headClickCallback = function (id) {
        var desc;
        if (this.lastSortParam === id) {
            desc = true;
            this.lastSortParam = '';
        } else {
            desc = false;
            this.lastSortParam = id;
        }
        this.sortParam = id;
        this.sortInstruments(id, desc);
        this.setMode(this.currentMode);
        this.refreshPortfolioHoldings();
    };