title: How to get selected chip choice values in flutter
body: <p>I've searched a lot on the internet but couldn't find the exact solution. How to get a list of selected Chips items
  I am passing the list of the object for option list values but unable to get the index of the selected item in <code>onChanged</code> method</p>
  <pre><code>          Container(
              child: FormField&lt;List&lt;Hashtag&gt;&gt;(
                autovalidate: true,
                initialValue: hashtagSelectedList,
                onSaved: (value) {
                  Utility.showToast(value.toString());
                  //hashtagSelectedList[0].hashtag = value.toString();
                },
                validator: (value) {
                  if (value.isEmpty) {
                    return 'Please select some categories';
                  }
                  if (value.length &gt; 5) {
                    return &quot;Can't select more than 5 categories&quot;;
                  }
                  return null;
                },
                builder: (state) {
                  return Column(
                    children: &lt;Widget&gt;[
                      Container(
                        alignment: Alignment.centerLeft,
                        child: ChipsChoice&lt;Hashtag&gt;.multiple(
                          value: state.value,
                          options: ChipsChoiceOption.listFrom&lt;Hashtag, Hashtag&gt;(
                            source: _hashtags,
                            value: (i, v) =&gt; v,
                            label: (i, v) =&gt; v.hashtag.toString(),
                          ),
                          onChanged: (val) {
                            if (val.length &gt; 5) {
                              Utility.showToast(
                                  &quot;Can't select more than 5 categories&quot;);
                              return;
                            }
                            state.didChange(val);
                          },
                          itemConfig: ChipsChoiceItemConfig(
                            showCheckmark: false,
                            selectedColor: Colors.indigo,
                            selectedBrightness: Brightness.dark,
                            unselectedColor: Colors.indigo,
                            unselectedBorderOpacity: .3,
                          ),
                          isWrapped: true,
                        ),
                      ),
                      Container(
                          padding: EdgeInsets.fromLTRB(15, 0, 15, 15),
                          alignment: Alignment.centerLeft,
                          child: Text(
                            state.errorText ?? state.value.toString(),
                            style: TextStyle(
                                color: state.hasError
                                    ? Colors.redAccent
                                    : Colors.green),
                          )),
                    ],
                  );
                },
              ),
            ),
  
   Option list - List&lt;Hashtag&gt; _hashtags; 
   Initial list - List&lt;Hashtag&gt; hashtagSelectedList; 
  
  Model -
     class Hashtag {
     int id;
     String hashtag;
    int status;
    bool isSelected = false;
  
    Hashtag();
  
    Hashtag.fromJson(Map&lt;String, dynamic&gt; json) {
      id = json[ApiKeys.id] ?? 0;
      hashtag = json[ApiKeys.hashtag] ?? '';
      status = json[ApiKeys.status] ?? 0;
    }
  }
  
  Please give me solutions 
  </code></pre>