code: function Once(event) {
        return Component.createDecorator(function (componentOptions, k) {
            var key = hyphenate(k);
            if (typeof componentOptions.created !== 'function') {
                componentOptions.created = function () { };
            }
            var original = componentOptions.created;
            componentOptions.created = function () {
                original();
                if (typeof componentOptions.methods !== 'undefined') {
                    this.$once(event || key, componentOptions.methods[k]);
                }
            };
        });
    }
docs: decorator of $once
  @param event The name of the event