如何使用包含模型配置的json文件动态创建Ext.data.Model实例

{
  "extend": "Ext.data.Model",
  "fields": [
    { "name": "id", "type": "int" },
    { "name": "name", "type": "string" },
    { "name": "age", "type": "int" }
  ]
}

Ext.require('Ext.data.ModelManager');

Ext.Ajax.request({
  url: 'model.json',
  success: function(response) {
    var modelConfig = Ext.decode(response.responseText);
    Ext.data.ModelManager.registerType(modelConfig.extend, modelConfig);
  }
});

var modelInstance = Ext.create('Ext.data.Model', {
  id: 1,
  name: 'John',
  age: 25
});