extjs4 rails 3 model validation for uniqueness - ruby-on-rails-3

Question

i m working with extjs 4 & rails 3.
I want to have validation for uniqueness of field that is on extjs form.
I want to have validation on Rails model for uniqueness, so i have done follwing on my rails model :
validates_uniqueness_of :search_key, :message => "Duplicate value found"
I am inserting new values of form into store as follows :
store.add(values);
If validation fails, the record does not get inserted into database.
Now I want to pop an alert box indicating that the entry is duplicate when validation fails, so that user can edit field.
How can i make this communication betwn rails controller & extjs form for validation?
Also would rails callback will be useful in it?

Answer 1

Here is how to pass messages returned from server to extjs app, I assume you can modify this to suit your need, or let me know if I need to clarify anything:
Extjs
in model, add:
proxy: {
type: 'rest',
url: '/manifest-items',
reader: {
type: 'json', // We expect the server to give us a JSON string as a response
root: 'rows',
totalProperty: 'total',
messageProperty: 'message',
}
},
Rails Controller
Then, in both cases of error or success, returned response should be:
render :json => {:success => false, :message => "some error", :rows => [something], :total => x}.to_json
Back to Extjs
In extjs, the message can be accessed as follows:
important: note the difference between getting error message in failure and success cases.
manifestItem.save({
success: function(records, operation) {
Ext.Msg.alert(operation.resultSet.message);
},
failure: function(records, operation) {
Ext.Msg.alert(operation.error);
}
});