title: Using Flutter Form Builder how to change the date value of FormBuilderDateTimePicker by adding the value of FormBuilderFieldOption
body: <p>I am a newbie to flutter and i'm trying to change the initialValue of flutter FormBuilderDateTimePicker on click over the one of the chips, created with FormBuilderChoiceChip. I need to add the value of each FormBuilderFieldOption under the FormBuilderChoiceChip to the initialValue of FormBuilderDateTimePicker.
  Here's the code:</p>
  <pre><code> child: Column(
                  children: &lt;Widget&gt;[
                   FormBuilderChoiceChip(
                     attribute: &quot;custom_days&quot;,
                     spacing: 3.0,
                     options: [
                       FormBuilderFieldOption(
                         child: Text(&quot;3 Days&quot;),
                                value: 3
                       ),
                       FormBuilderFieldOption(
                         child: Text(&quot;5 Days&quot;),
                                value: 5
                       ),
                       FormBuilderFieldOption(
                         child: Text(&quot;7 Days&quot;),
                                value: 7
                       ),
                     ],
                    ),
                    FormBuilderDateTimePicker(
                      attribute: &quot;date&quot;,
                      inputType: InputType.date,
                      format: DateFormat(&quot;dd-MM-yyyy&quot;),
                      decoration: InputDecoration(labelText: &quot;Select Date&quot;),
                      initialValue: DateTime.now(),
                    )
                   ]
                  )
  </code></pre>
  <p>here is the image of the output:
  <a href="https://i.stack.imgur.com/exMoP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/exMoP.png" alt="enter image description here" /></a>
  on click over each chip, the value should be added to the initialvalue of the date and and get update to the future date.</p>