Extending Grid Feature?

[haochi]

Hi,

I am trying to extend Grid summary feature but it's throwing an error

Uncaught TypeError: Cannot read property 'childNodes' of null 

Here's the code sample, modified from http://docs.sencha.com/extjs/4.2.1/#...eature.Summary

Ext.define('TestResult', {    extend: 'Ext.data.Model',    fields: ['student', {        name: 'mark',        type: 'int'    }]});Ext.define('Ext.grid.feature.Summary2', {    extend: 'Ext.grid.feature.Summary',    alias: 'feature.summary2'});Ext.create('Ext.grid.Panel', {    width: 400,    height: 200,    title: 'Summary Test',    style: 'padding: 20px',    renderTo: document.body,    features: [{        ftype: 'summary2'    }],    store: {        model: 'TestResult',        data: [{            student: 'Student 1',            mark: 84        }, {            student: 'Student 2',            mark: 72        }, {            student: 'Student 3',            mark: 96        }, {            student: 'Student 4',            mark: 68        }]    },    columns: [{        dataIndex: 'student',        text: 'Name',        summaryType: 'count',        summaryRenderer: function(value, summaryData, dataIndex) {            return Ext.String.format('{0} student{1}', value, value !== 1 ? 's' : '');        }    }, {        dataIndex: 'mark',        text: 'Mark',        summaryType: 'average'    }]}); 

[carol.ext]

The summary feature has the view look it up in one of its functions using view.findFeature('summary');

renderTFoot: function(values, out) {
        var view = values.view,
            me = view.findFeature('summary');

        if (me.showSummaryRow) {
            out.push('<tfoot>');
            me.outputSummaryRecord(me.createSummaryRecord(view), values, out);
            out.push('</tfoot>');
        }
    },

Including that function in the summary2 feature updating the lookup to 'summary2' made it work, although less than optimal.

Ext.define('Ext.grid.feature.Summary2', {
    extend: 'Ext.grid.feature.Summary',
    alias: 'feature.summary2',
    
     renderTFoot: function(values, out) {
        var view = values.view,
            me = view.findFeature('summary2');

        if (me.showSummaryRow) {
            out.push('<tfoot>');
            me.outputSummaryRecord(me.createSummaryRecord(view), values, out);
            out.push('</tfoot>');
        }
    }
    
});

I looked at the 5.01 code and the same lookup is in there, just in a different function (renderSummaryRow).