ExtJS - null safe retrieval of complex objects using JsonReader

Question

I am using a JsonReader to map Json data to variables to be used in a grid/form. The back end is in Java and there are complex objects which I Jsonify and pass to the ExtJS front end. This is a part of my JsonReader which tries to retrieve a nested object -

{name:'status', type: 'string', mapping: 'status.name'}

This works fine when status has a value (not null in the server), but the grid load fails when status is null. Currently the work around I have is to send an empty object from the server in case of null, but I assume there should be a way to handle this in ExtJS. Please suggest a better solution on the ExtJS side.

Answer 1

I can think of two possibilities - one documented and one undocumented:

1. use the convert()-mechanism of Ext.data.Field:

   {
       name:'status', 
       mapping: 'status',
       convert: function(status, data) {
           if (!Ext.isEmpty(status) && status.name) {
               return status.name;
           } else {
               return null;
           }
       }
   }
   

2. The mapping property can also take an extractor function (this is undocumented so perhaps it may be a little bit risky to rely on this):

   {
       name:'status', 
       mapping: function(data) {
           if (data.status && data.status.name) {
               return data.status.name;
           } else {
               return null;
           }
       }
   }