Knockout.js : manually trigger computed

Question

I have a grid and a select control on the page. Choosing any select value triggers grid update. That updating is done using computed. Can I manually trigger grid to update, say, in situation when a new value is added to a grid?

 function vm(){
    var self = this;

    self.items = ko.observableArray([]);
    self.chosen_category = ko.observable("");

    self.pager = {
        page_namber : ko.observable(1),
        page_size : ko.observable(10)
    };

     self.sort = {
       field : ko.observable('name'),
       dist : ko.observable('asc')
     };
     // etc. 

     self.fetch = ko.computed(function(){
        $.ajax({
               url: '/api/items/',
               type: 'GET',
               data: ko.toJSON(self),
               contentType: 'application/json',
               success: self.items
          });
     }, self);


      self.add_item = function() {
        //here I want to update the grid
        self.fetch(); // not work
      };
 }

Sure I can move it to a separate function but I am looking for a cleaner solution. Thanks!

working version :

          function vm() {
            var self = this;

            self.items = ko.observableArray([]);
            self.chosen_category = ko.observable("test");

            self.pager = {
                page: ko.observable(1),
                size: ko.observable(10)
            };

            self.sort = {
                field: ko.observable('name'),
                dist: ko.observable('asc')
            };

            self.fetch = function () {
                var data = {
                    category: self.chosen_category(),
                    pager: ko.toJS(self.pager),
                    sort: ko.toJS(self.sort)
                };

                $.ajax({
                    url: '/api/items/',
                    type: 'POST',
                    data: ko.toJSON(data),
                    contentType: 'application/json',
                    success: self.items
                });
            };

            self._auto_update = ko.computed(self.fetch).extend({ throttle: 1 }); ;

            self.add_item = function () {
                self.fetch();
            };
        }

Answer 1

It is better to do this with subscription instead of computed. In that case you can define fetch function to use for both subscription and manual call:

function vm(){
  var self = this;

  self.items = ko.observableArray([]);
  self.chosen_category = ko.observable("");

  self.fetch = function(){   
    $.get('/api/items/' + self.chosen_category(), self.items);
  };

  self.chosen_category.subscribe(self.fetch);


  self.add_item = function() {
   //here I want to update the grid
   self.fetch(); 
  };
}

Also you can do the same with computed:

function vm(){
  var self = this;

  self.items = ko.observableArray([]);
  self.chosen_category = ko.observable("");

  self.fetch = function(){   
    $.get('/api/items/' + self.chosen_category(), self.items);
  };

  self.doStaff = ko.computed(self.fetch);


  self.add_item = function() {
   //here I want to update the grid
   self.fetch(); 
  };
}