Dynamic Model

I want to make an Ajax request before the store config to load its model dynamically. But every time the config method is compiled first.AventoCrm.app.x is my global variable. Tell me the right way to do so.

Ext.Ajax.request({

url: AventoCrm.app.storeUrl+'(\'Dialogue\')/fields',

headers:{

'Accept':'application/json;odata=verbose'

},

success: function(response) {

try{

var resp = response.responseText;

if(resp) {

var data = Ext.JSON.decode(resp);

fields = [{

name: 'id'

}];

for(var i = 0, len = data.d.results.length; i < len; i++){

// AventoCrm.app.DialogueFields.push({name:data.d.results[i].InternalName});

fields[i+1] = {

name: data.d.results[i].InternalName

}

}

AventoCrm.app.x=Ext.define('AventoCrm.model.DialogueModel', {extend: 'Ext.data.Model',fields:fields});

alert(fields[1].name);

alert(AventoCrm.app.x);

}

}catch(e){

console.error(e);

}

},

failure: function(e){

console.error(e);

}

});

Ext.define('AventoCrm.store.DialogueStore',{

extend: 'Ext.data.Store',

requires: [

// 'AventoCrm.model.DialogueModel',

'Ext.data.proxy.Ajax',

'Ext.data.reader.Xml'

],

config: {

autoLoad: true,

autoSync: true,

model: AventoCrm.app.x,

storeId: 'DialogueStore',

proxy: {

type: 'rest',

url: AventoCrm.app.storeUrl+'(\'Dialogue\')/items',

reader: {

type: 'xml',

record: 'entry'

}

}

}

});