Question

Is it possible to do this process in ExtJS 4.1.x ?

var myMixedCollection = myStore.queryBy(...);
var anotherStore = Ext.create('Ext.data.Store', { data: myMixedCollection, ... });
var myGrid = Ext.create('Ext.grid.Panel', { store: anotherStore, ... });

Because my grid displays nothing or just one empty line.
When I log my myMixedCollection there is no problem all data are here but when I open my anotherStore with Firebug i can see there is only one empty line in my data store.

Answer 1

myMixedCollection will be a collection of records (model instances) and as long as the new store hast the same model set this will work! So the answer is Yes

Well, for sure you need to call getRange() on the myMixedCollection instance

Here is a working example

 // Set up a model to use in our Store
 Ext.define('Simpson', {
     extend: 'Ext.data.Model',
     fields: [
         {name: 'name', type: 'string'},
         {name: 'email', type: 'string'},
         {name: 'phone', type: 'string'}
     ]
 });

var s1 = Ext.create('Ext.data.Store', {
    model:'Simpson',
    storeId:'simpsonsStore',
    fields:['name', 'email', 'phone'],
    data:{'items':[
        { 'name': 'Lisa',  "email":"[e-mail]",  "phone":"555-111-1224"  },
        { 'name': 'Bart',  "email":"[e-mail]",  "phone":"555-222-1234" },
        { 'name': 'Homer', "email":"[e-mail]",  "phone":"555-222-1244"  },
        { 'name': 'Marge', "email":"[e-mail]", "phone":"555-222-1254"  }
    ]},
    proxy: {
        type: 'memory',
        reader: {
            type: 'json',
            root: 'items'
        }
    }
});

var mixed = s1.queryBy(function(rec){
     if(rec.data.name == 'Lisa')
         return true;
});

var s1 = Ext.create('Ext.data.Store', {
    model:'Simpson',
    storeId:'simpsonsStore2',
    fields:['name', 'email', 'phone'],
    data: mixed.getRange(),
    proxy: {
        type: 'memory',
        reader: {
            type: 'json'
        }
    }
});

Ext.create('Ext.grid.Panel', {
    title: 'Simpsons',
    store: Ext.data.StoreManager.lookup('simpsonsStore2'),
    columns: [
        { text: 'Name',  dataIndex: 'name' },
        { text: 'Email', dataIndex: 'email', flex: 1 },
        { text: 'Phone', dataIndex: 'phone' }
    ],
    height: 200,
    width: 400,
    renderTo: Ext.getBody()
});

and the JSFiddle