This is something I had to do as well myself and I took the same approach of overriding the getRecordData function to take into account the associations. I also added some code to take care of deleted records as well. I'm adding a forDeletion property only for deleted records so that I can keep it out of the fields on the models.
Code:
Ext.data.writer.Json.override({
/*
* This function overrides the default implementation of json writer. Any hasMany relationships will be submitted
* as nested objects. When preparing the data, only children which have been newly created, modified or marked for
* deletion will be added. To do this, a depth first bottom -> up recursive technique was used.
*/
getRecordData: function(record) {
//Setup variables
var me = this, i, association, childStore, data = record.data;
//Iterate over all the hasMany associations
for (i = 0; i < record.associations.length; i++) {
association = record.associations.get(i);
data[association.name] = null;
childStore = record[association.storeName];
//Iterate over all the children in the current association
childStore.each(function(childRecord) {
if (!data[association.name]){
data[association.name] = [];
}
//Recursively get the record data for children (depth first)
var childData = this.getRecordData.call(this, childRecord);
/*
* If the child was marked dirty or phantom it must be added. If there was data returned that was neither
* dirty or phantom, this means that the depth first recursion has detected that it has a child which is
* either dirty or phantom. For this child to be put into the prepared data, it's parents must be in place whether
* they were modified or not.
*/
if (childRecord.dirty | childRecord.phantom | (childData != null)){
data[association.name].push(childData);
record.setDirty();
}
}, me);
/*
* Iterate over all the removed records and add them to the preparedData. Set a flag on them to show that
* they are to be deleted
*/
Ext.each(childStore.removed, function(removedChildRecord) {
//Set a flag here to identify removed records
removedChildRecord.set('forDeletion', true);
var removedChildData = this.getRecordData.call(this, removedChildRecord);
data[association.name].push(removedChildData);
record.setDirty();
}, me);
}
//Only return data if it was dirty, new or marked for deletion.
if (record.dirty | record.phantom | record.get('forDeletion')){
return data;
}
}
});
I'm not sure if this code will work under every condition but it's been fine for me so far. If you have any suggestions for improvements or a better way of doing it I'd like to hear your thoughts.