javascript - Cascading the convert function for a nested model in ExtJS 5 -

i have grid i'd fill translatable strings in extjs 5. in past i've translated strings using convert method, in case need translations in nested model , convert method firing @ top level. ideas on making cascade?

ext.define('application.model.messageconfig', { extend : "application.model.base", fields: [     {         name: 'messagetype',         reference: 'messagetype',         unique: true     },     {         name: 'subscribedapp',         type: 'boolean'     },     {         name: 'subscribedemail',         type: 'boolean'     } ] });   ext.define('application.model.messagetype', { extend : "application.model.base",  mixins: [     'elsevier.localization.translate.util' ],  constructor: function(){     this.inittranslate();     this.callparent(arguments); },  fields: [     {         name: 'messagetypeid',         type: 'int'     },     {         name: 'status',         type: 'string'     },     {         name: 'reftablecategory',         type: 'reftable'     },     {         name: 'nametranslationkey',         type: 'string',         convert: function (value, data){             debugger;             var code = data.get('nametranslationkey');             if(code) {                 return data.i18n[code];             }             return '';         }     },     {         name: 'descriptiontranslationkey',         type: 'string',         convert: function (value, data){             var code = data.get('descriptiontranslationkey');             if(code) {                 return data.i18n[code];             }             return '';         }     },     {         name: 'manageable',         type: 'boolean'     },     {         name: 'modifiableapp',         type: 'boolean'     },     {         name: 'modifiableemail',         type: 'boolean'     },     {         name: 'defaultsubscriptionapp',         type: 'boolean'     },     {         name: 'defaultsubscriptionemail',         type: 'boolean'     },     {         name: 'type',         type: 'string',     } ],  belongsto: 'messagesconfig' });