Invalid field for AggregateResult while creating apex chart

Question

I am trying to create an apex chart. While running i am getting the following error -

Invalid field Product__r.Family for AggregateResult

public list<wrapperclass> getPieData() {
 List<wrapperclass> data = new List<wrapperclass>();

List<Work_Order_Item__c> memb = new List<Work_Order_Item__c>();             


 AggregateResult[] groupedResults  = [SELECT count(Id),Product__r.Family FROM Work_Order_Item__c group by Product__r.Family];

 for (AggregateResult ar : groupedResults)  {            
                    if(ar.get('Product__r.Family')!=null)
                    {
                     data.add(new wrapperclass(
                         String.ValueOf(ar.get('Product__r.Family')),
                         Double.ValueOf(ar.get('expr0'))
                         ));
                    }    
             }      
             return data;

}

Vf Page -

<apex:chart height="350" width="450" data="{!pieData}">
            <apex:pieSeries dataField="data" labelField="Name"/>
            <apex:legend position="bottom"/>
        </apex:chart>

Error Javascript -

SfdcCore.js:384 Visualforce Chart: Error loading configuration for chart 'jid0jid1pbjid3jid4': Unable to infer data model from result: result is not an Arrayb.resolve.b.provide.log @ SfdcCore.js:384
https://login.salesforce.com/17181/logo180.png Failed to load resource: the server responded with a status of 404 (Not Found)

Can anyone tell what i am doing wrong.

Answer 1

The aggregate case is bit different to normal SOQL so I think this is what is needed:

AggregateResult[] groupedResults  = [
        SELECT count(Id) c, Product__r.Family f
        FROM Work_Order_Item__c
        WHERE Product__r.Family != null
        GROUP BY Product__r.Family
        ];
for (AggregateResult ar : groupedResults)  {            
    data.add(new wrapperclass(
            String.ValueOf(ar.get('f')),
            Double.ValueOf(ar.get('c'))
            ));
}