dynamic column and rows with knockoutjs

Question

My input parameter for the code below is just a tablename,

I was able to query the data return in json format, however, i am not able to display my rows item of data. any idea what did i do wrong?

<script>
var invtype = "@ViewBag.invtype";

    function ViewModel() {  

        var self = this;
        function ColName(tbstruct){ 
            this.ColumnName = tbstruct.ColumnName
        }

        self.TBStruct = ko.observableArray(); 
        self.items = ko.observableArray(); 

        self.invtype = invtype;

        self.Load = function () {


    //expected data for self.items
    //[{"$id":"1","Id":2,"Inv_Id":"PV0001-1","ACX_No":"6","ACX_Name":"ABC","S_No":"5", "Acc_Class":"Local","Direction":"Two-Way"},{"$id":"2","Id":2,"Inv_Id":"PV0002-1","ACX_No":"3","ACX_Name":"CKD","S_No":"6", "Acc_Class":"Local","Direction":"Two-Way"}]


            $.ajax({
                    url: "@Url.Content("~/api/")"+self.invtype, 
                    type: 'GET',
                    dataType: 'JSON',
                    success: function (data) {
                        // Map the returned JSON to the View Model  

                        self.items = data;
                    }
            });

//expected data
     //[{"$id":"1","ColumnName":"Id","system_type_id":56,"primaryCol":1}, {"$id":"2","ColumnName":"Inv_Id","system_type_id":231,"primaryCol":0},{"$id":"3","ColumnName":"ACX_No","system_type_id":175,"primaryCol":0},{"$id":"4","ColumnName":"ACX_Name","system_type_id":175,"primaryCol":0},{"$id":"5","ColumnName":"S_No","system_type_id":175,"primaryCol":0} {"$id":"27","ColumnName":"Acc_Class","system_type_id":231,"primaryCol":0},{"$id":"28","ColumnName":"Direction","system_type_id":231,"primaryCol":0} ]

            $.ajax({
                    url: "@Url.Content("~/api/inventories/")"+self.invtype,
                    type: 'GET',
                    dataType: 'JSON',
                    success: function (data) {
                        // Map the returned JSON to the View Model  
                        $.each(data,function(i,dt){
                            //console.log(dt.ColumnName);
                            self.TBStruct.push(new ColName(dt));
                        });
                        //console.dir(self.TBStruct);
                    }
            });
            return self;
        };
    } 

    var View = new ViewModel();
    ko.applyBindings(View.Load()); 

here i am trying to display them out.

    <thead>
        <tr data-bind="foreach: TBStruct">
            <th data-bind="text: ColumnName"></th>
        </tr>
    </thead>

    <tbody >
        <tr data-bind="foreach: items" >
            <td data-bind="text:$data"></td> 
        </tr> 
    </tbody>
</table>

Answer 1

function ViewModel() {
    var self = this;

    self.invtype = "@ViewBag.invtype";
    self.columns = ko.observableArray();
    self.rows = ko.observableArray();

    self.load = function () {
        $.when(
            $.get("@Url.Content('~/api/inventories/')" + self.invtype),
            $.get("@Url.Content('~/api/')" + self.invtype)
        )
        .then(function (columnResponse, rowResponse) {
            var columnDefs = columnResponse[0],
                rowDefs = rowResponse[0],
                columnMapping = {
                    key: function (data) {
                        return ko.utils.unwrapObservable(data.ColumnName);
                    }
                },
                rowMapping = {
                    key: function (data) {
                        return ko.utils.unwrapObservable(data.Id);
                    }
                };

            ko.mapping.fromJS(columnDefs, columnMapping, self.columns);
            ko.mapping.fromJS(rowDefs, rowMapping, self.rows);
        });

        return self;
    };
}

Notes:

• Using jQuery's .when() and .then() ensures that view model processing occurs only after both HTML requests have returned successfully. See jQuery's documentation on the topic.
• The key function in the custom mapping ensures that when you call load() again then only the appropriate parts of your view model get an update. Otherwise ko.mapping.fromJS will replace the entire observable, resulting in a complete re-build of the affected part of your page. Specifying key allows partial page updates, so use a unique property of your data here. (If you don't plan on refreshing data from the server during page life time this step might not be necessary.)
• The use of ko.utils.unwrapObservable() is mandatory because during a load operation key will be used on both the existing view model contents and the server response, so for example data.ColumnName could be an observable or a raw value.
• Be sure to read through the advanced section of the mapping plugin documentation, you might find other helpful bits.

HTML

<table>
    <thead>
        <tr data-bind="foreach: $root.columns">
            <th data-bind="text: ColumnName"></th>
        </tr>
    </thead>
    <tbody data-bind="foreach: $root.rows">
        <tr data-bind="foreach: $root.columns">
            <td data-bind="text: $parent[ColumnName()]"></td>
        </tr>
    </tbody>
</table>

Notes:

• The only place where $root is actually necessary is in the <tr data-bind="foreach: $root.columns"> binding. The others are just included for consistency.
• $parent refers to the row from foreach: $root.rows.
• The parentheses in $parent[ColumnName()] are necessary because ColumnName is an observable and in a complex binding they are not unwrapped automatically.

The whole thing can be seen here: http://jsfiddle.net/Tomalak/A6T8p/
and here (extended version): http://jsfiddle.net/Tomalak/A6T8p/1