EXTJS7 store数据格式预处理

Ext.create('Ext.data.Store', {
    model: 'User',
    proxy: {
        type: 'ajax',
        url : 'users.json',
        reader: {
            type: 'json',
            transform: {
                fn: function(data) {
                    // 对原始数据对象进行处理操作
                    return data;
                },
                scope: this
            }
        }
    },
});

// data/reader/Json.js
...
getResponseData: function(response) {
	...
	return Ext.decode(response.responseText);
	...
}
...
// data/reader/Reader.js
...
read: function(response, readOptions) {
	...
	result = this.getResponseData(response);
	...
	data = this.readRecords(result, readOptions);
	...
}
...
readRecords: function(data, readOptions, internalReadOptions) {
	...
	transform = me.getTransform();
    if (transform) {
        data = transform(data);
    }
	...
}
...