title: flutter add controller to an inputfield
body: <p>i have a inputfield in a a widget to get the user email, i need to add a controller to this, but if i add the controller: line then i get an error:</p>
  
  <pre><code>  child: new Column(
            children: &lt;Widget&gt;[
              new InputField(
                ****controller: emailController,******
                  hintText: email,
                  obscureText: false,
                  textInputType: TextInputType.text,
                  textStyle: loginFormTextStyle,
                  textFieldColor: textFieldColor,
                  icon: Icons.mail_outline,
                  iconColor: Colors.blue,
                  bottomMargin: 20.0,
                  validateFunction: validations.validateEmail,
                  onSaved: (String email) {
                    user.email = email;
                  }),
  </code></pre>
  
  <p>how i can add the controller to this input without change the inputfield to a inputtextfield?</p>
  
  <p>thanks</p>